Participation of the HIM1 gene of yeast Saccharomyces cerevisiae in the error-free branch of post-replicative repair and role Polη in him1-dependent mutagenesis

Abstract

In eukaryotes, DNA damage tolerance (DDT) is determined by two repair pathways, homologous repair recombination (HRR) and a pathway controlled by the RAD6-epistatic group of genes. Monoubiquitylation of PCNA mediates an error-prone pathway, whereas polyubiquitylation stimulates an error-free pathway. The error-free pathway involves components of recombination repair; however, the factors that act in this pathway remain largely unknown. Here, we report that the HIM1 gene participates in error-free DDT. Notably, inactivation RAD30 gene encoding Polη completely suppresses him1-dependent UV mutagenesis. Furthermore, data obtained show a significant role of Polη in him1-dependent mutagenesis, especially at non-bipyrimidine sites (NBP sites). We demonstrate that him1 mutation significantly reduces the efficiency of the induction expression of RNR genes after UV irradiation. Besides, this paper presents evidence that significant increase in the dNTP levels suppress him1-dependent mutagenesis. Our findings show that Polη responsible for him1-dependent mutagenesis.

Genetic Analysis of the Hsm3 Protein Function in Yeast Saccharomyces cerevisiae NuB4 Complex

“…At the same time, double mutant showed high UV resistance than the single rad30∆. We observed the same tendency in the case of him1∆ rad30∆ mutant [44]. Thus, we can conclude that, in during PRR the Polη in hsm3∆ mutant carries out reparative synthesis in unfilled gaps.…”

“…From this, it follows that the change of polymerases occurs after the destruction of the D-loop and the gap is filled with an erroneous polymerase. We observed the same events in him1∆ mutant [44].…”

“…Interaction between RAD30 and HSM3: Evidence has been obtained showing that HSM3 and HIM1 genes play a role in stabilizing the D-loops [42,44]. Earlier, we showed that after the destruction of the D-loop in the him1 mutant, Polη fills the remaining gap (44). Based on these data, we hypothesized that the cause of hsm3-mediated UV-induced mutagenesis as well as him1-dependent UV-mutagenesis is the replacement of Polδ with highly erroneous Polη.…”

“…Interaction between RAD30 and HSM3: Evidence has been obtained showing that HSM3 and HIM1 genes play a role in stabilizing the D-loops [ 42 , 44 ]. Earlier, we showed that after the destruction of the D-loop in the him1 mutant, Polη fills the remaining gap (44).…”

“…In order to find out the ratio of UV-induced mutations in non- and bipyrimidine sites in mutant rad30 , mutation spectra were determined at the CAN1 locus in hsm3Δ strain. We used the same scheme and experimental conditions as in the work with him1Δ mutant [ 44 ]. 100 can R mutants were isolated after UV irradiation at a dose 84 J/m 2 .…”