Nav: Home

Microbe breaks 'universal' DNA rule by using two different translations

June 14, 2018

DNA is often referred to as the blueprint for life, however scientists have for the first time discovered a microbe that uses two different translations of the DNA code at random. This unexpected finding breaks what was thought to be a universal rule, since the proteins from this microbe cannot be fully predicted from the DNA sequence.

Researchers from the Milner Centre for Evolution at the University of Bath and the Max-Planck Institute for Biophysical Chemistry in Göttingen, Germany have published their findings in the journal Current Biology.

All organisms receive genetic information from their parents which tell the cells how to make proteins - the molecules that do the chemistry in our bodies. This genetic information comprises DNA molecules made up of a sequence of four chemical bases represented by the letters A, T, C and G; the genetic code dictates to the cell which sequence of amino acids to join together to form each protein given the underlying sequence in the DNA.

In a similar way that "dot dot dot" in morse code translates as S, so too the genetic code is read in blocks of three bases (codons) to translate to one amino acid.

It was originally thought that any given codon always results in the same amino acid - just as dot dot dot always means S in morse code. GGA in the DNA for example translates as the amino acid glycine.

However a collaboration between Dr Stefanie Mühlhausen and Professor Laurence Hurst at the Milner Centre for Evolution at the University of Bath, and Martin Kollmar and colleagues at the Max-Planck Institute for Biophysical Chemistry in Göttingen, Germany have now described the first - and unexpected - exception to this rule in a natural code.

The group examined an unusual group of yeasts in which some species have evolved an unusual non-universal code. While humans (and just about everything else) translate the codon CTG as the amino acid leucine, some of the species of yeast instead translate this as the amino acid serine whilst others translate it as alanine.

This is odd enough in itself. But the team was even more surprised to find one species, Ascoidea asiatica, randomly translated this codon as serine or leucine. Every time this codon is translated the cell tosses a chemical coin: heads for leucine, tails it's serine.

Laurence Hurst, Professor of Evolutionary Genetics and Director of the Milner Centre for Evolution at the University of Bath, said: "This is the first time we've seen this in any species.

"We were surprised to find that about 50 per cent of the time that CTG is translated as serine, the remainder of the time it is leucine.

"The last rule of genetics codes, that translation is deterministic, has been broken. This makes this genome unique - you cannot work out the proteins if you know the DNA."

To understand how this happens - how this coin-toss mechanism is physically manifested - the team investigated molecules called tRNAs - which act as translators that recognise the codons and bring together the amino acids to make a protein chain.

Dr Martin Kollmar, from the Max-Planck Institute for Biophysical Chemistry in Göttingen said: "We found that Ascoidea asiatica, is unusual in having two sorts of tRNAs for CTG - one which bridges with leucine and one which bridges with serine.

"So when CTG comes to be translated, it randomly picks one of the two tRNAs and hence randomly picks between serine and leucine."

Dr Stefanie Mühlhausen from The Milner Centre for Evolution at the University of Bath added: "Swapping a serine for leucine could cause serious problems in a protein as they have quite different properties - serine is often found on the surface of the protein whereas leucine is hydrophobic and often buried inside the protein.

"We looked at how this strange yeast copes with this randomness and found that A. asiatica has evolved to use the CTG codon very rarely and especially avoids key parts of proteins."

The researchers estimate that the random encoding is 100 million years old, but other closely related species evolved to lose this potentially problematic trait.

Dr Martin Kollmar said: "It's unclear why A. asiatica should have retained this stochastic encoding for so long. Perhaps there are rare occasions when this sort of randomness can be beneficial."
-end-
The research was funded by the European Research Council and Medical Research Council.

University of Bath

Related Dna Articles:

Scientists now know what DNA's chaperone looks like
Researchers have discovered the structure of the FACT protein -- a mysterious protein central to the functioning of DNA.
In one direction or the other: That is how DNA is unwound
DNA is like a book, it needs to be opened to be read.
DNA is like everything else: it's not what you have, but how you use it
A new paradigm for reading out genetic information in DNA is described by Dr.
A new spin on DNA
For decades, researchers have chased ways to study biological machines.
From face to DNA: New method aims to improve match between DNA sample and face database
Predicting what someone's face looks like based on a DNA sample remains a hard nut to crack for science.
Self-healing DNA nanostructures
DNA assembled into nanostructures such as tubes and origami-inspired shapes could someday find applications ranging from DNA computers to nanomedicine.
DNA design that anyone can do
Researchers at MIT and Arizona State University have designed a computer program that allows users to translate any free-form drawing into a two-dimensional, nanoscale structure made of DNA.
DNA find
A Queensland University of Technology-led collaboration with University of Adelaide reveals that Australia's pint-sized banded hare-wallaby is the closest living relative of the giant short-faced kangaroos which roamed the continent for millions of years, but died out about 40,000 years ago.
DNA structure impacts rate and accuracy of DNA synthesis
DNA sequences with the potential to form unusual conformations, which are frequently associated with cancer and neurological diseases, can in fact slow down or speed up the DNA synthesis process and cause more or fewer sequencing errors.
Changes in mitochondrial DNA control how nuclear DNA mutations are expressed in cardiomyopathy
Differences in the DNA within the mitochondria, the energy-producing structures within cells, can determine the severity and progression of heart disease caused by a nuclear DNA mutation.
More Dna News and Dna Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

In & Out Of Love
We think of love as a mysterious, unknowable force. Something that happens to us. But what if we could control it? This hour, TED speakers on whether we can decide to fall in — and out of — love. Guests include writer Mandy Len Catron, biological anthropologist Helen Fisher, musician Dessa, One Love CEO Katie Hood, and psychologist Guy Winch.
Now Playing: Science for the People

#543 Give a Nerd a Gift
Yup, you guessed it... it's Science for the People's annual holiday episode that helps you figure out what sciency books and gifts to get that special nerd on your list. Or maybe you're looking to build up your reading list for the holiday break and a geeky Christmas sweater to wear to an upcoming party. Returning are pop-science power-readers John Dupuis and Joanne Manaster to dish on the best science books they read this past year. And Rachelle Saunders and Bethany Brookshire squee in delight over some truly delightful science-themed non-book objects for those whose bookshelves are already full. Since...
Now Playing: Radiolab

An Announcement from Radiolab