Biologists uncover a novel cellular proofreading mechanism

Nov 11, 2011

(PhysOrg.com) -- To make proteins, cells assemble long chains of amino acids, based on genetic instructions from DNA. That construction takes place in a tiny cellular structure called a ribosome, to which amino acids are delivered by transfer RNA (tRNA).

Each of the 20 amino acids encoded by the is carried by a specific type of tRNA. The matching between amino acid and tRNA must be precise, or else the wrong amino acid will be added to the protein.

A team of MIT researchers has now discovered that cells have a proofreading mechanism that destroys any malformed tRNA molecules. This ensures that only the correct amino acids are used, preventing proteins from being misassembled.

The finding is reported in the Nov. 10 issue of the journal Science. Lead author of the paper is Jeremy Wilusz, a postdoc in the David H. Koch Institute for Integrative at MIT. Senior author of the paper is Phillip Sharp, Institute Professor at MIT.

It was already known that all tRNAs, which are made of nucleotides, just like DNA, have a CCA sequence at one end, which is where an amino acid can latch onto the tRNA. This CCA is added to the tRNA after it is transcribed from DNA, by an enzyme called the CCA-adding enzyme. Without CCA, the tRNA would be nonfunctional.

The new study shows that the CCA-adding enzyme can also add a CCACCA sequence. This sequence is added to abnormal tRNAs – those with a mutation or a structural flaw. The CCACCA tag marks the tRNA for destruction by other enzymes called exonucleases.

“It’s a way to prevent these mistakes, by taking the tRNA out of service and not giving it the chance to add the wrong amino acid,” says Wilusz. “If it can’t quite fold right, the structure falls apart a little bit and everything’s a bit more flimsy, so you’re able to add this second CCA.”

The researchers observed this mechanism in species from all kingdoms of life.

Explore further: How plant cell compartments change with cell growth

Related Stories

Giant tablets aimed at families

49 minutes ago

Costing a little more than an iPad but standing more than twice as tall, a new pair of giant tablets wants families to share cozier group experiences with technology.

Restaurants experimenting with pay-in-advance tickets

2 hours ago

With restaurant patrons increasingly jumping on the Internet to make reservations, some high-end eateries here and across the country are adding a new tech wrinkle: having their clientele pay for their meal in advance using ...

Recommended for you

How plant cell compartments change with cell growth

Aug 22, 2014

A research team led by Kiminori Toyooka from the RIKEN Center for Sustainable Resource Science has developed a sophisticated microscopy technique that for the first time captures the detailed movement of ...

Plants can 'switch off' virus DNA

Aug 22, 2014

A team of virologists and plant geneticists at Wageningen UR has demonstrated that when tomato plants contain Ty-1 resistance to the important Tomato yellow leaf curl virus (TYLCV), parts of the virus DNA ...

A better understanding of cell to cell communication

Aug 22, 2014

Researchers of the ISREC Institute at the School of Life Sciences, EPFL, have deciphered the mechanism whereby some microRNAs are retained in the cell while others are secreted and delivered to neighboring ...

A glimpse at the rings that make cell division possible

Aug 22, 2014

Forming like a blown smoke ring does, a "contractile ring" similar to a tiny muscle pinches yeast cells in two. The division of cells makes life possible, but the actual mechanics of this fundamental process ...

User comments : 0