Enzyme necessary for DNA synthesis can also erase DNA

June 8, 2009

In this week's edition of Proceedings of the National Academy of Sciences, PNAS, Uppsala University scientists describe a new mechanism behind an important process that causes a rapid reduction of DNA in the chromosomes of bacteria. The findings advance our knowledge of how DNA content has been reduced, which is something that has occurred in bacteria that live as parasites inside the cells of other organisms.

The amount of DNA in the chromosomes of bacteria can change rapidly, either by increasing, so-called gene amplification, or by decreasing, so-called gene deletion. These processes are evolutionarily very important, and the discovery of a new mechanism that is involved when DNA disappears is of fundamental importance to our understanding what influences the stability of chromosomes and why the amount of DNA can decrease in certain types of bacteria. "How rapidly and by what mechanisms DNA can disappear from the chromosome is a central genetic and evolutionary question," says Professor Dan I Andersson, the lead author of the study.

Previously these types of large gene deletions, have mostly been studied in artificial model systems with two long identical and neighboring . Normal spontaneous deletions, on the other hand, are often remote from each other and lack sequence identity.

In the current study, the PhD student Sanna Koskiniemi has carried out comprehensive genetic analyses of Salmonella mutants and her results show that a

special type of DNA-synthesizing enzymes are necessary if spontaneous deletions are to be formed in the bacteria. This new function has never before been described in these enzymes. By genetically inactivating or overproducing these enzymes, the researchers were able to show that the deletion rates decreased or increased by up to 30 times.

These findings can explain how and why the DNA content of different organisms varies and what govern this, says Professor Dan Andersson, who suggests that bacteria that live either as parasites inside cells or in symbiosis with other organisms are of special interest with regard to this new mechanism.

These bacteria often have small chromosomes because DNA has disappeared during evolution. With these new findings we can better understand and predict how DNA is eliminated from .

Source: Uppsala University (news : web)

Explore further: Blending bacterial genomes for megacloning

Related Stories

Mass copying of genes speeds up evolution

October 31, 2006

In the latest issue of PNAS, Proceedings of the National Academy of Sciences, a Swedish-American team of researchers show how selective gene amplification-­mass copying of a specific gene­-can increase the speed with which ...

Fungi can tell us about the origin of sex chromosomes

March 17, 2008

Fungi do not have sexes, just so-called mating types. A new study being published today in the prestigious journal PLoS shows that there are great similarities between the parts of DNA that determine the sex of plants and ...

Recommended for you

How the finch changes its tune

August 3, 2015

Like top musicians, songbirds train from a young age to weed out errors and trim variability from their songs, ultimately becoming consistent and reliable performers. But as with human musicians, even the best are not machines. ...

Machine Translates Thoughts into Speech in Real Time

December 21, 2009

(PhysOrg.com) -- By implanting an electrode into the brain of a person with locked-in syndrome, scientists have demonstrated how to wirelessly transmit neural signals to a speech synthesizer. The "thought-to-speech" process ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.