Identification of pathways controlling DNA damage induced mutation in Saccharomyces cerevisiae.

Mutation in response to most types of DNA damage is thought to be mediated by the error-prone sub-branch of post-replication repair and the associated translesion synthesis polymerases. To further understand the mutagenic response to DNA damage, we screened a collection of 4848 haploid gene deletion strains of Saccharomyces cerevisiae for decreased damage-induced mutation of the CAN1 gene. Through extensive quantitative validation of the strains identified by the screen, we identified ten genes, which included error-prone post-replication repair genes known to be involved in induced mutation, as well as two additional genes, FYV6 and RNR4.

Phosphatases, DNA damage checkpoints and checkpoint deactivation.

Cells have evolved intricate and specialized responses to DNA damage, central to which are the DNA damage checkpoints that arrest cell cycle progression and facilitate the repair process. Activation of these damage checkpoints relies heavily on the activity of Ser/Thr kinases, such as Chk1 and Chk2 (Saccharomyces cerevisiae Rad53), which are themselves activated by phosphorylation. Only more recently have we begun to understand how cells disengage the checkpoints to reenter the cell cycle.

Pph3-Psy2 is a phosphatase complex required for Rad53 dephosphorylation and replication fork restart during recovery from DNA damage.

Activation of the checkpoint kinase Rad53 is a critical response to DNA damage that results in stabilization of stalled replication forks, inhibition of late-origin initiation, up-regulation of dNTP levels, and delayed entry to mitosis. Activation of Rad53 is well understood and involves phosphorylation by the protein kinases Mec1 and Tel1 as well as in trans autophosphorylation by Rad53 itself. However, deactivation of Rad53, which must occur to allow the cell to recover from checkpoint arrest, is not well understood.

Role of Doa1 in the Saccharomyces cerevisiae DNA damage response.

The cellular response to DNA damage requires not only direct repair of the damage but also changes in the DNA replication machinery, chromatin, and transcription that facilitate survival. Here, we describe Saccharomyces cerevisiae Doa1, which helps to control the damage response by channeling ubiquitin from the proteosomal degradation pathway into pathways that mediate altered DNA replication and chromatin modification. DOA1 interacts with genes involved in PCNA ubiquitination, including RAD6, RAD18, RAD5, UBC13, and MMS2, as well as genes involved in histone H2B ubiquitination or deubiquitination, including RAD6, BRE1, LGE1, CDC73, UBP8, UBP10, and HTB2.