The Saccharomyces cerevisiae Rad6 postreplication repair and Siz1/Srs2 homologous recombination-inhibiting pathways process DNA damage that arises in asf1 mutants

Mol Cell Biol. 2009 Oct;29(19):5226-37. doi: 10.1128/MCB.00894-09. Epub 2009 Jul 27.


The Asf1 and Rad6 pathways have been implicated in a number of common processes such as suppression of gross chromosomal rearrangements (GCRs), DNA repair, modification of chromatin, and proper checkpoint functions. We examined the relationship between Asf1 and different gene products implicated in postreplication repair (PRR) pathways in the suppression of GCRs, checkpoint function, sensitivity to hydroxyurea (HU) and methyl methanesulfonate (MMS), and ubiquitination of proliferating cell nuclear antigen (PCNA). We found that defects in Rad6 PRR pathway and Siz1/Srs2 homologous recombination suppression (HRS) pathway genes suppressed the increased GCR rates seen in asf1 mutants, which was independent of translesion bypass polymerases but showed an increased dependency on Dun1. Combining an asf1 deletion with different PRR mutations resulted in a synergistic increase in sensitivity to chronic HU and MMS treatment; however, these double mutants were not checkpoint defective, since they were capable of recovering from acute treatment with HU. Interestingly, we found that Asf1 and Rad6 cooperate in ubiquitination of PCNA, indicating that Rad6 and Asf1 function in parallel pathways that ubiquitinate PCNA. Our results show that ASF1 probably contributes to the maintenance of genome stability through multiple mechanisms, some of which involve the PRR and HRS pathways.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Cell Cycle Proteins / genetics*
  • Cell Cycle Proteins / metabolism
  • Chromosomes, Fungal
  • DNA Damage
  • DNA Helicases / genetics*
  • DNA Helicases / metabolism
  • DNA Repair*
  • DNA Replication
  • DNA, Fungal / genetics
  • DNA, Fungal / metabolism
  • Hydroxyurea / pharmacology
  • Methyl Methanesulfonate / pharmacology
  • Molecular Chaperones / genetics*
  • Molecular Chaperones / metabolism
  • Mutation
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism
  • Recombination, Genetic*
  • S Phase
  • Saccharomyces cerevisiae / cytology
  • Saccharomyces cerevisiae / drug effects
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / genetics*
  • Saccharomyces cerevisiae Proteins / metabolism
  • Ubiquitin-Conjugating Enzymes / genetics*
  • Ubiquitin-Conjugating Enzymes / metabolism
  • Ubiquitin-Protein Ligases / genetics*
  • Ubiquitin-Protein Ligases / metabolism
  • Ubiquitination


  • ASF1 protein, S cerevisiae
  • Cell Cycle Proteins
  • DNA, Fungal
  • Molecular Chaperones
  • Saccharomyces cerevisiae Proteins
  • SRS2 protein, S cerevisiae
  • Methyl Methanesulfonate
  • RAD6 protein, S cerevisiae
  • Ubiquitin-Conjugating Enzymes
  • Ubiquitin-Protein Ligases
  • DUN1 protein, S cerevisiae
  • Protein-Serine-Threonine Kinases
  • DNA Helicases
  • Siz1 protein, S cerevisiae
  • Hydroxyurea