Breakthough in understanding of how mutations occur in genes

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Breakthough in understanding of how mutations occur in genes

http://www.news-medical.net/?id=27574

For the first time, it can now be shown what enzyme copies the

genetic make-up of cells.

The discovery is being published in the journal Science by

researchers at Umea University in Sweden in collaboration with a

team in the U.S. led by A. Kunkel.

The human genome has already been mapped, as have the genomes of

several other organisms. On the other hand, little has been known

how genes are copied and repaired so efficiently and precisely.

These processes always involve a so-called DNA polymerase, an enzyme

that performs the actual new growth of genes. The genes consist of

two DNA strands, but scientists have not known what polymerase

copies the two DNA strands. It has been known, however, that DNA

polymerase epsilon is responsible for a great deal of this synthesis

in higher organisms, and that it does so with the greatest precision.

The researchers describe in the article how they mutated DNA

polymerase epsilon, creating an enzyme that makes a particular error

when it copies genes. This means that the enzyme leaves a signature

at all sites where it copies the genes in the cell.

By reading where this signature is left, the scientists have then

been able to determine that DNA polymerase epsilon copies one of the

strands, the so-called " leading " strand. For decades researchers

have been wondering what enzyme synthesizes this particular part,

and now proof has been found.

These research findings, which describe fundamental biological

functions, pave the way for an enhanced understanding of how

mutations occur in genes, mutations that can lead to cancer, for

instance.

Contributors from Umea University are Johansson, a researcher

at the Department of Medical Biochemistry and Biophysics, together

with doctoral student Isabelle Isoz and laboratory assistant Else-

Britt Lundström. The U.S. authors Zacchary Pursell and A.

Kunkel work at the National Institute of Environmental Health

Sciences, NIH.

Johansson's research is described in greater detail in the Ume?

niversity project database: http://www.info.umu.se/fodb/Projekt.aspx?

id=29

http://www.adm.umu.se