The
contribution of Pol Zeta, Rev1p and Pol Eta in UV induced mutagenesis in Saccharomyces
cerevisiae.
Ana I. Belo (1),
Tineke de Ruijter (1), Hans den Dulk (1), Marcel Tijsterman (1), Leon
Mullenders (2), Jaap Brouwer (1)
(1) Molecular Genetics, Leiden Institute of Chemistry, Einsteinweg 55, Leiden,
2333 CC, The Netherlands (a.i.van.wijk@chem.leidenuniv.nl); (2) Department of
Radiation Genetics and Chemical Mutagenesis, Leiden University, Wassenaarseweg
72, 2333 AL Leiden, The Netherlands
The cell
developed diversified means of repairing lesions occurring in DNA upon
ultra-violet (UV) radiation. When this first line of defense fails, specialized
translesion polymerases are required to rescue blocked replication forks. Three
translesion synthesis polymerases are known in yeast: Rev1p, Polymerase (Pol)
Zeta and Pol Eta. In order to analyze the contribution of these polymerases in
mutagenesis in Saccharomyces cerevisiae, URA3 mutation spectrums were
made. Our data show that Pol Zeta and Rev1p insert preferentially a T or an A
opposite a UV damaged C or T. One third of the basepair substitutions were
found opposite thymine-thymine (TT) dimers where a T was inserted opposite the
damaged base. Although Rev1p is essential for all mutations in a rad30 background, only 3% of
the basepair substitutions found were C's inserted opposite the damaged base.
This implicates that inserting a C against a damaged base is not the only role
of Rev1p in translesion synthesis. Pol Eta inserts adenines opposite an UV
damaged dimer, thus contributing to UV mutagenesis by inserting A's opposite to
damaged C's. All mutations found were CG>TA transitions. Therefore, Pol Eta
functions as an A rule polymerase when replicating UV damaged DNA.