Originally published as Genetics Published Articles Ahead of Print on June 18, 2008.

Genetics, Vol. 179, 1197-1210, July 2008, Copyright © 2008
doi:10.1534/genetics.108.089003

Role of Dot1 in the Response to Alkylating DNA Damage in Saccharomyces cerevisiae: Regulation of DNA Damage Tolerance by the Error-Prone Polymerases Pol{zeta}/Rev1

Francisco Conde and Pedro A. San-Segundo1

Instituto de Microbiología Bioquímica, Consejo Superior de Investigaciones Científicas and University of Salamanca, 37007 Salamanca, Spain

1 Corresponding author: Instituto de Microbiología Bioquímica, CSIC-USAL, Edificio Departamental Lab 313-316, Campus Unamuno, 37007 Salamanca, Spain.
E-mail: pedross{at}usal.es

Maintenance of genomic integrity relies on a proper response to DNA injuries integrated by the DNA damage checkpoint; histone modifications play an important role in this response. Dot1 methylates lysine 79 of histone H3. In Saccharomyces cerevisiae, Dot1 is required for the meiotic recombination checkpoint as well as for chromatin silencing and the G1/S and intra-S DNA damage checkpoints in vegetative cells. Here, we report the analysis of the function of Dot1 in the response to alkylating damage. Unexpectedly, deletion of DOT1 results in increased resistance to the alkylating agent methyl methanesulfonate (MMS). This phenotype is independent of the dot1 silencing defect and does not result from reduced levels of DNA damage. Deletion of DOT1 partially or totally suppresses the MMS sensitivity of various DNA repair mutants (rad52, rad54, yku80, rad1, rad14, apn1, rad5, rad30). However, the rev1 dot1 and rev3 dot1 mutants show enhanced MMS sensitivity and dot1 does not attenuate the MMS sensitivity of rad52 rev3 or rad52 rev1. In addition, Rev3-dependent MMS-induced mutagenesis is increased in dot1 cells. We propose that Dot1 inhibits translesion synthesis (TLS) by Pol{zeta}/Rev1 and that the MMS resistance observed in the dot1 mutant results from the enhanced TLS activity.