Chemical key to cell division revealed

In each of our cells, most of the genetic material is packaged safely within the nucleus, which is protected by a double membrane. The biochemistry behind how this membrane transforms when cells divide has finally been unravelled, offering insights that could provide new ways of fighting cancer and some rare genetic disorders.

During cell division, the membrane that surrounds the nucleus breaks down and reforms in the two daughter cells. Researchers have been split on the precise mechanisms that govern membrane reformation. One view is that proteins alone control the membrane's transformations. Another possibility is that changes in lipids – a vast group of fat-related compounds – are responsible.

Experiments had failed to show which of these two ideas was right, because it was difficult to alter lipid levels in specific compartments of cells without affecting other cellular processes.

Banafshe Larijani at Cancer Research UK's London Research Institute and her colleagues have now overcome that hurdle. They came up with a technique that transforms a type of lipid called a diacylglycerol (DAG) into another lipid, within the nuclear membrane.

Chemical cascade

The technique involves inserting two fragments of DNA into the nucleus of a cell. This causes the cell to make two proteins: the first attaches itself to the nuclear membrane, the second floats around the cell. Adding a drug – rapalogue – to the mix causes the second protein to stick to the first, which in turn causes a chemical cascade that transforms the DAG into a different kind of lipid.

Crucially, they targeted a form of DAG that does not bind to proteins, so converting it into a different lipid does not affect any processes involving proteins in the cell.

The team tested the effect of this lipid manipulation on cell division in monkey and human cancer cells. The lower the level of DAG present in the nuclear membrane, the greater the membrane malformation and chance of cell death.

This demonstrates that lipids play a role in nuclear membrane reformation that does not depend on proteins.

Larijani says it "opens the door to finding ways to kill cancerous cells" by focusing on lipids that are important to the nuclear membrane's development.

Sausage pieces

As the nucleus divides, sausage-shaped fragments of its membrane float around the cell. The fragments have curved ends, and Larijani says that changes in lipid composition generate these curves, without which the fragments cannot reassemble correctly into new membranes.

More than a dozen rare genetic conditions such as Hutchinson-Gilford progeria syndrome, which is characterised by premature ageing in children, have been linked to irregularities in cell division. A better understanding of the way the nuclear membrane forms when cells divide could be key to treating these disorders.

The research also offers a new focus for preventing the irregular cell division that underlies many cancers.

"As a result of this work we now know with confidence that DAG plays a structural role in membrane dynamics," says Vytas Bankaitis, at the Texas A&M Health Science Center in College Station, who was not involved in the study. "If we could find a molecule with suitable characteristics, this manipulation could be done [in humans], which is something that has not really been considered before."

Journal reference: PLoS ONE DOI: 10.1371/journal.pone.0051150

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.

All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.

If you are having a technical problem posting a comment, please contact technical support.

Read More..

Three dead, 8 missing in North Sea cargo ship collision

THE HAGUE: Rescuers pulled at least three bodies from the icy waters of the North Sea on Wednesday and were frantically searching for eight missing crew from a cargo ship that sank following a collision in a busy shipping lane off the Dutch coast.

The Dutch coastguard and navy plucked 13 survivors from the water after the Baltic Ace, a 23,000 tonne car carrier, collided with container ship the Corvus J at around 7:15 pm (1815 GMT) about 100 kilometres (60 miles) from Rotterdam.

The Baltic Ace sank shortly afterwards, the coastguard said.

"I can confirm we have found three victims. Eight others are still missing," Marcel Oldenburger told AFP.

He said that 13 crew members who were on board the Bahamas-registered Baltic Ace had been rescued.

Four survivors were flown to a hospital in Rotterdam, seven taken by rescue helicopter to a hospital in Belgium and two were being treated on board a ship that found them, Oldenburger said.

"They are all in shock" and are believed to suffer from hypothermia, he said.

Oldenburger said the search for survivors was frantic: "We don't know where they are at the moment, whether they are in life boats, or in the sea."

At least three helicopters -- one of which was fitted out with infrared imaging equipment to search in the darkness -- and a plane have joined the search, Oldenburger said.

The Baltic Ace was under way from Zeebrugge in Belgium to Kotka in Finland and the Corvus J from Grangemouth in Scotland to Antwerp in Belgium, according to shipping tracker website MarineTraffic.com.

"At this stage we don't know what caused the accident," said another coastguard spokesman, Peter Verburg: "Our first priority right now is the safety of the crew."

The shipping lane where the accident happened is one of the busiest in the North Sea and an important passing point for ships sailing into Rotterdam port, Europe's largest and the fifth-largest in the world.

Rotterdam port spokesman Sjaak Poppe told AFP the collision would not affect shipping in and out of the port.

In one of the most serious collisions in Dutch waters in recent years, the Greek crude oil tanker Mindoro in October 2010 collided with the container ship Jork Ranger off the coast of Scheveningen near The Hague, spilling thousands of litres of kerosene (jet fuel) into the sea, the European Maritime Safety Agency said on its website.

-AFP/ac

Read More..

AT&T says true 4G is coming in 2013, but will it beat Verizon?

Soon to up the ante?

(Credit:
AT&T)

If the rumors are true, real, honest-to-god 4G in the United States could be on the way sometime in the next 7 to 12 months. FierceWireless reports on word from AT&T's annual meeting with analysts that it will be "firing up" new "LTE Advanced" service across its network in the second half of 2013.

What is LTE Advanced? Well, it's a lot like 4G LTE, only more, um, advanced.

See, in the old days of mobile broadband -- like, all the way back in 2011 -- carriers started marketing services they called 4G, but in the real world, they really only offered speeds one-tenth or one-twentieth those of the actual 4G standard, which is meant to deliver download speeds in the range of 100Mbps. That means we were suddenly able to download full songs out of the air in mere seconds on these new 4G services.

That's right, I said seconds instead of the single second it should be taking us over true 4G. And thus we were robbed in the name of marketing. After all, who wants to wait five full seconds to download "Party Rock Anthem?"

But now it looks like next year will produce a savior in the form of a carrier to deliver us to a land of true 4G LTE Advanced with extra cheese... or whatever.

Sprint has LTE Advanced on their roadmaps as well, but was only talking speeds of 15Mbps at last check.

So if AT&T winds up as the first company that can actually deliver triple-digit Mbps speeds, we may finally stop poking fun at the company's one-time inability to deliver consistent service without dropped calls and dead zones in the biggest of American cities.

That's right my fellow soldiers of snark, it may finally be time to make nice with the big blue deathstar, for this may be the year we all fall to our knees and beg AT&T to bring its new network to our towns.

Then again, by that time it could all be a moot point, as Verizon's CEO claimed this week that by the time the other guys are making their next big 4G moves, Big Red will already be looking at 5G and 6G networks.

Read More..

Large, Peanut-Shaped Asteroid Headed Toward Earth

A giant asteroid is set to buzz Earth next week, and astronomers are already keeping their eyes on the skies—but not because 4179 Toutatis poses any danger.

Toutatis, at 2.7 miles (4.46 kilometers) long and 1.5 miles (2.4 kilometers) wide, is one of the largest asteroids that comes anywhere near Earth. But only an astronomer would consider its closest approach to be "near." When the peanut-shaped rock is at its closest to the Earth on December 12, it'll be more than 4.3 million miles (6.9 million kilometers) away, or more than 18 times the distance from the Earth to the moon.

(See pictures of asteroids.)

So why are astronomers eagerly awaiting Toutatis? By figuring out what the asteroid is made of, they'll have a better picture of the early days of the solar system. And by refining a model of the asteroid's rotation, they'll get a better idea of its composition.

Topsy-Turvy

Michael Busch, a fellow at the National Radio Astronomy Observatory, studied radar images of Toutatis' previous passes—the asteroid approaches Earth every four years—to try to figure out how it was moving through space. "It's tumbling," Busch said. "It's spinning around its long axis, while that in turn is precessing around in a circle, like a gyroscope." Busch and his colleagues were hoping to use radar images taken in 2000, 2004, and 2008 to update a 1996 model of Toutatis' spin state. "[But] this became more complicated when we understood that [gravitational] tides were changing the spin," he said.

Every time Toutatis came close to the sun or the Earth, gravity would tug slightly on the asteroid, changing its spin by a tiny fraction. But over the years, those tugs added up. Once Busch and his collaborators were able to account for these changes, they had a much better model of its spin. And that told them how the asteroid's mass was distributed.

Toutatis is shaped sort of like a lumpy peanut, or from some angles, like a poorly built snowman. It's long and narrow, with two distinct lobes, one smaller than the other. Busch's analysis found that the asteroid's shape isn't the only thing that's lumpy; its mass is also distributed in a lumpy fashion rather than evenly spread throughout the asteroid. "It may have a quite complicated internal structure," he said.

Inner Workings

It's possible the asteroid got its internal structure when a smaller body smashed into it, throwing material off. "That can fracture it, just like hitting a surface with a hammer," Busch said.

Toutatis could also have been created when two objects collided and stuck.

Or, it could have been created through the YORP effect, which explains how nothing but sunlight can cause an asteroid to start spinning. "Wind blowing on a propeller makes the propeller spin," said Dan Scheeres, an astrodynamics professor at the University of Colorado, Boulder, who's been studying Toutatis for almost two decades. And that's similar to what happens when photons hit an uneven body, making that body spin faster, he added. Scheeres thinks that a faster-spinning Toutatis could have eventually spun so fast that it began throwing off material into space, becoming two separate bodies. These bodies would have eventually slowed down and recombined, starting the process over again.

It's still just a theory, Scheeres said, but the model explains how Toutatis and other so-called contact binaries could exist.

Scheeres and Busch will be analyzing their new observations of Toutatis as it gets closer to Earth over the next week; Busch plans to refine his model of the asteroid's spin after seeing the new radar images.

But astronomers aren't the only ones who will be able to see Toutatis on its flyby. Backyard hobbyists can get in on the fun too. At its closest approach, Toutatis will be "too faint to see with the naked eye, but well within the range of a small backyard telescope," Busch said.

(Learn about telescopes.)

And no, it's not going to hit Earth, so doomsday theorists, relax.

(Learn about potentially hazardous asteroids.)

"There may be more nonsense circulating about Toutatis than many other objects, but that's because it's a large object that makes repeated close flybys of Earth and has an interesting shape," he said.

The new Toutatis data on density and spin state was presented at the 45th annual fall meeting of the American Geophysical Union.

Read More..

WH 'Absolutely' Willing to Go Off Fiscal Cliff

President Obama's lead negotiator in the "fiscal cliff" talks said the administration is "absolutely" willing to allow the package of deep automatic spending cuts and across-the-board tax hikes to take effect Jan. 1, unless Republicans drop their opposition to higher income tax rates on the wealthy.

Treasury Secretary Timothy Geithner said in an interview with CNBC that both sides are "making a little bit of progress" toward a deal to avert the "cliff" but remain stuck on Obama's desired rate increase for the top U.S. income-earners.

"There's no prospect for an agreement that doesn't involve those rates going up on the top two percent of the wealthiest," Geithner said.

Most House Republicans, including Speaker John Boehner, remain opposed to any increase in tax rates.

Obama and Boehner spoke by phone this afternoon, their first conversation in exactly one week, an administration official said. Their relations have grown frosty in recent days as both sides have dug in on the issue of higher rates.

In separate appearances earlier today, Obama and Boehner publicly sparred over who's to blame for the standoff and what to do if lawmakers can't reach a broad deficit-reduction agreement in 27 days.

Saul Loeb/AFP/GettyImages

Fiscal Cliff: What Republicans, Democrats Agree on So Far Watch Video

'Fiscal Cliff': John Boehner Makes Counteroffer Watch Video

Washington, D.C., Gridlocked as Fiscal Cliff Approaches Watch Video

Obama, speaking at a meeting of 100 CEOs, warned Republicans that he would not accept a so-called "doomsday" deal that extends tax cuts for middle-income earners before the end of the year but nothing more.

Such an approach, which has been under consideration by top Republicans as a likely scenario, would set the stage for a big battle over spending cuts and top tax rates in early 2013 – all tied to the nation's debt ceiling, which will need to be raised, which only Congress can do.

"That is a bad strategy for America, it's bad strategy for businesses," Obama said. "It's not a game I will play."

Brinksmanship over the a 2011 debt ceiling increase to avoid a U.S. default cost the country its AAA credit rating and rattled markets around the world.

While both sides say publicly that the U.S. will not default on its debt obligations, Republicans believe the issue could give them increased leverage for extracting cuts to entitlement programs and other spending.

Boehner said at a morning news conference that Obama has stifled the "fiscal cliff" negotiations by imposing the precondition that Republicans accept income tax hikes on the top 2 percent of U.S. earners.

"We're ready and eager to talk to the president and to work with him to make sure that the American people aren't disadvantaged by what's happening here in Washington," Boehner said at a morning news conference.

"We need a response from the White House," he said. "We can't sit here and negotiate with ourselves."

Earlier this week, House Republicans presented a $2.2 trillion deficit reduction package, including $800 billion in higher taxes through elimination of loopholes and deductions, slower annual cost-of-living increases for Social Security benefits and a higher eligibility age for Medicare.

The plan contrasts sharply with the White House proposal, which calls for $1.6 trillion in new tax revenue -- largely from higher rates on upper-income earners -- modest unspecified savings from Medicare and a new burst of economic stimulus spending.

Both sides rejected the opposing plan as "unserious."

Read More..

When is a baby too premature to save?

It was never easy, but trying to decide whether to save extremely premature babies just got harder.

A study called EPICure compared the fates of babies born 22 to 26 weeks into pregnancy in the UK in 1995 with similar babies born in 2006. In this 11-year period, the babies surviving their first week rose from 40 to 53 per cent. But an accompanying study comparing the fate of survivors at age 3 found that the proportion developing severe disabilities was unchanged, at just under 1 in 5.

"We've increased survival, but it's confined to the first week of life," says Kate Costeloe of Queen Mary, University of London, author of the first study. "Yet the pattern of death and health problems is strikingly similar between the two periods."

The absolute numbers of premature babies born over the 11 year period increased by 44 per cent, from 666 in 1995 to 959 in 2006. This meant that the absolute numbers of children with severe disabilities such as blindness, deafness or lameness also rose, increasing the burden on health, educational and social services.

Lifelong disability

"As the number of children that survive preterm birth continues to rise, so will the number who experience disability throughout their lives," says Neil Marlow of University College London, who led the second study.

By far the worst outcomes were for the youngest babies, with 45 per cent of those born at 22 or 23 weeks in 2006 developing disabilities compared with 20 per cent of those born at 26 weeks. In 1995 only two babies survived after being born at 22 weeks. In 2006, three did.

In 2006, a panel of UK ethicists concluded that babies born at 22 weeks should be allowed to die, as with babies born at or before 23 weeks in France and Holland.

Journal references: BMJ, Costeloe et al, DOI: 10.1136/bmj.e7976; Marlow et al, DOI: 10.1136/bmj.e7961

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.

All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.

If you are having a technical problem posting a comment, please contact technical support.

Read More..

Football: Zenit secure Europa spot

MILAN, Italy: A 35th minute strike from Danny secured a 1-0 away win over seven-time champions AC Milan and a Europa League spot for Russia side Zenit St Petersburg here on Tuesday.

With qualification secured two weeks ago, Milan coach Massimiliano Allegri could afford to rest a number of regulars including top scorer Stephan El Shaarawy, midfielder Riccardo Montolivo and defender Philippe Mexes.

However, Allegri's plan almost backfired, with fans leaving the stadium early as the dominant hosts tried but failed to find a leveller to Danny's superb first-half strike.

Zenit had been condemned to perform as well as Anderlecht did away to Malaga to hold on to third place in Group C and a Europa League last 32 spot.

And despite seeing his side defend for long periods as Milan laid siege to the visitors' area Zenit held on for a win which Spalletti did not seem too overwhelmed with.

"I'm happy with the qualification (for Europa) and how we played tonight, it's good we are still in Europe," said Spalletti, who grew up 70 km away from Allegri in Tuscany.

"Winning is important but maybe a draw would have been a fairer result as we ended up defending a lot."

He added: "We have to come back stronger and qualify for the knockout phase the next time because this club, this team deserves it."

Spalletti sent out his strongest possible side, with Hulk spearheading the attack flanked by Danny and Sergei Semak and Bruno Alves marshalling the defence in front of the experienced Vyacheslav Malafeev.

And on one of their few forays into the Milan area Danny pounced to send a superb curling shot past the outstretched Christian Abbiati to secure victory.

"I'm sorry about the defeat, but only in the sense the team put in a good, solid performance. The guys didn't deserve it," said Allegri.

"Otherwise it was a positive performance, we forced Zenit to defend for most of the match and they scored in what was practically their only chance of the opening half."

Milan should have had several goals, especially in the second half when the Russians seemed happy to sit on their lead.

The Rossoneri's hopes for an early opener, however, were snuffed out by the referee who waved away what appeared to be a valid penalty claim after Alves felled Giampaolo Pazzini from behind in the fourth minute.

When Zenit broke the deadlock, Milan's makeshift defence was caught on the hoof, Danny picking up a backpass from his own through ball to beat Abbiati with a well placed shot at the keeper's far post.

Milan responded immediately but attempts by Bojan and Flamini, the latter with a rasping drive which forced a good block from Malafeev, came to nothing.

Milan came close to levelling minutes after the restart when Urby Emanuelson got his foot to Kevin Prince Boateng's cross from the right after a superb counter-attack orchestrated by defender Francesco Acerbi, only for Malafeev to block superbly.

Pazzini then flashed a header wide from Emanuelson's cross, and when Bojan was allowed space to run down on goal he sent his 20-metre drive wayward.

Allegri replaced left-back Djamel Mesbah with Robinho just after the hour mark, and his through ball allowed Bojan to run through with the goal at his mercy on 74 minutes only for the Spaniard to be dispossessed as he wound up to shoot.

With 10 minutes remaining, El Shaarawy replaced Flamini, although it was Robinho who came closest to beating Malafeev when he curled a sublime shot just wide of Malafeev's far post.

El Shaarawy followed up moments later with a shot on the turn which edged just wide of the upright.

Zenit had enjoyed little time in Milan's area in the second half but almost embarrassed the hosts with a three-on-two scenario which only the alert Abbiati thwarted with a superb block from substitute Maksim Kanunnikov's shot in the closing minutes.

- AFP/fa

Read More..

Apple's Eddy Cue lets go of $8.76M in stock

Eddy Cue, Apple's iCloud and music chief at Apple's iPhone 5 event earlier this year.

(Credit:
James Martin/CNET)

Apple's
iTunes, iCloud and Maps chief Eddy Cue let go of a portion of company stock last Friday, a new filing shows.

According to a filing with the U.S. Securities and Exchange Commission this afternoon, last week Cue sold off 15,000 shares, worth just under $584 on average.

The total sale was worth just under $8.76 million.

Cue was promoted to senior vice president last September, a month after Tim Cook took the helm as CEO. As part of the promotion Cue oversaw iTunes, iCloud, iAd, and Apple's iBookstore. With an executive shuffle in November, Cue was also given responsibility of Apple's Siri voice assistant product, as well as its homegrown mapping service as part of an "online services" group.

Before making too much out of last week's sale, Cue was given a hearty bonus of 100,000 restricted stock units last November, designed to keep him and others there for the long haul. The first bunch of those shares vest on September 21, 2014, reliant on Cue continuing to work at Apple.

Cue's sell off comes a day after a sale of 35,000 shares by fellow Apple SVP Bob Mansfield, who pulled in around $20 million from the sale.

Read More..

Oldest Giant Panda Relative Found in Spain

The oldest relative of the giant panda has been discovered in Spain—suggesting that the animals' ancestors originated in Europe, a new study says.

Dubbed Kretzoiarctos beatrix, the 11-million-year-old species was previously named Agriarctos beatrix based on a few fossil teeth found at a paleontological site near Zaragoza, Spain (map). Agriarctos is an extinct genus of European bear and a possible panda ancestor that lived eight to nine million years ago. (Read about the previous research.)

Earlier this year, scientists found a piece of A. beatrix's jaw, allowing them to compare it with that of another ancient Agriarctos bear from Hungary. In doing so, the team determined that A. beatrix is actually its own genus, which they called Kretzoiarctos.

The newly named K. beatrix pushes back the origin of giant pandas by a few million years, making it the oldest recorded giant panda relative, said study leader Juan Abella, a paleobiologist at the Museo Nacional de Ciencias Naturales in Madrid, Spain.

"Therefore, the origin of this group is not located in China, where the [giant panda] species lives, but in the warm and humid regions of [southwestern] Europe," Abella said in May.

(See: "Ancient Bear DNA Mapped—A First for Extinct Species.")

New Bear Was Panda-Like?

K. beatrix likely shared some similarities with today's giant panda.

For one, says Abella, the newfound jaw fragment shows the animal was likely an omnivore that fed on tough plants, like modern-day pandas. Also like them, and like most existing species of small bears, K. beatrix was probably a great climber. According to Abella, it would have had to scramble up trees to escape big predators of the day—such as extinct, doglike carnivores called bear-dogs—in the forests of what's now Spain.

But at 130 pounds (60 kilograms), K. beatrix was smaller than modern pandas and even more petite than the modern-day sun bear or spectacled bear.

(See "Biggest Bear Ever Found-'It Blew My Mind,' Expert Says.")

An Epic Trek?

It's still unclear how panda ancestors made the epic trek from Europe to China.

Previous research suggests bears generally can migrate easily if the climate is mild enough, Abella said. Eleven million years ago, southwestern Europe was warm and humid-good conditions for starting out, he said.

The bears likely migrated mostly on land. One potential barrier—an ancient European sea called Parathetys—was already shrinking during the Middle Miocene, when K. beatrix lived, said Abella.

As for whether K. beatrix made it to China, "We don't really know, but no fossil remains of this species have been found outside Spain."

Whatever its history, the new research shows that K. beatrix was not your average bear.

The oldest panda relative study was published November 14 in the journal PLoS ONE.

Read More..

Obama Sees 'Potential' for Averting the Fiscal Cliff

President Obama says he sees "potential" for averting the "fiscal cliff" in 28 days, but that no deal will get done unless Republicans consent to raise income-tax rates on the top 2 percent of U.S. earners.

"We're going to have to see the rates on the top 2 percent go up and we're not going to be able to get a deal without it," Obama told Bloomberg TV in his first televised interview since the Nov. 6 election.

Obama suggested that Republican opposition to any increase in tax rates has stifled progress in negotiations and at least partly explains why he has not met more regularly with House Speaker John Boehner.

"Speaker Boehner and I speak frequently," he said. "I don't think the issue right now has to do with sitting in a room.

"Unfortunately, the speaker's proposal right now is still out of balance," he added, referring to the GOP plan unveiled Monday that would extend all income tax rates at current levels while imposing changes to Medicare and Social Security.

The GOP proposal would achieve $2.2 trillion in deficit reduction in the next decade, including $800 billion in higher taxes through elimination of loopholes and deductions, slower annual cost-of-living increases for Social Security benefits and a higher eligibility age for Medicare.

Jessica Kourkounis/Getty Images

Washington, D.C., Gridlocked as Fiscal Cliff Approaches Watch Video

What Exactly Did Obama Promise Voters on Tax Hikes Watch Video

'Fiscal Cliff' Negotiations: Ball Is in the GOP's Court Watch Video

The plan contrasts sharply with the White House proposal, which calls for $1.6 trillion in new tax revenue -- largely from higher rates on upper-income earners -- modest unspecified savings from Medicare and a new burst of economic stimulus spending.

Both sides have dismissed out of hand the opposing proposal, raising the prospect of continued gridlock as the economy hurdles toward the "cliff."

Income tax rates for the top 2 percent of Americans remain the immediate sticking point. Obama insists that rates must rise at the end of the year as part of any deal; Republicans oppose increasing rates on the wealthy.

Unless Obama and Republicans reach a compromise, a sweeping set of automatic, across-the-board tax hikes and deep spending cuts will take effect, potentially throwing the U.S. economy back into recession.

The "cliff" scenario results from a failure by Congress and the administration at previous intervals to take steps to reduce federal deficits and debt.

In the Bloomberg interview, Obama said he could be flexible on tax rates and entitlement overhaul, but only in broader discussions next year about revamping the tax code and social safety-net programs.

"Let's let [rates on higher-income earners] go up and then let's set up a process with a time certain at the end of 2013, or the fall of 2013, where we work on tax reform, we look at what loopholes and deductions both Democrats and Republicans are willing to close and it's possible that we may be able to lower rates by broadening the base at that point," he said.

The president also said he's "willing to look at anything" that might strengthen entitlements and extend their financial solvency, but did not specify further.

Republicans continued to rebuff the president's proposal Tuesday, claiming the $1.6 trillion package of tax increases could not pass either house of Congress, including the Democrat-controlled Senate.

"Only one person in the country can deliver the members of his party to support a deal that he makes, and that is the president," said Senate Minority Leader Mitch McConnell.

He praised House Republicans for "trying to move the process forward" with their proposal, but stopped short of endorsing it. Some conservative advocacy groups have been assailing GOP leaders this week for consenting to any tax revenue increases in a deal with Obama.

"With our latest offer we have demonstrated there is a middle ground solution that can cut spending and bring in revenue without hurting American small businesses," Boehner said in a statement today.

Read More..