Role of Saccharomyces cerevisiae Chromatin Assembly Factor-I in Repair of Ultraviolet Radiation Damage in Vivo

Abstract

In vitro, the protein complex Chromatin Assembly Factor-I (CAF-I) from human or yeast cells deposits histones onto DNA templates after replication. In Saccharomyces cerevisiae, the CAC1, CAC2, and CAC3 genes encode the three CAF-I subunits. Deletion of any of the three CAC genes reduces telomeric gene silencing and confers an increase in sensitivity to killing by ultraviolet (UV) radiation. We used double and triple mutants involving cac1Δ and yeast repair gene mutations to show that deletion of the CAC1 gene increases the UV sensitivity of cells mutant in genes from each of the known DNA repair epistasis groups. For example, double mutants involving cac1Δ and excision repair gene deletions rad1Δ or rad14Δ showed increased UV sensitivity, as did double mutants involving cac1Δ and deletions of members of the RAD51 recombinational repair group. cac1Δ also increased the UV sensitivity of strains with defects in either the error-prone (rev3Δ) or error-free (pol30-46) branches of RAD6-mediated postreplicative DNA repair but did not substantially increase the sensitivity of strains carrying null mutations in the RAD6 or RAD18 genes. Deletion of CAC1 also increased the UV sensitivity and rate of UV-induced mutagenesis in rad5Δ mutants, as has been observed for mutants defective in error-free postreplicative repair. Together, these data suggest that CAF-I has a role in error-free postreplicative damage repair and may also have an auxiliary role in other repair mechanisms. Like the CAC genes, RAD6 is also required for gene silencing at telomeres. We find an increased loss of telomeric gene silencing in rad6Δ cac1Δ and rad18Δ cac1Δ double mutants, suggesting that CAF-I and multiple factors in the postreplicative repair pathway influence chromosome structure.

Cac1 WHD and PIP domains have distinct roles in replisome progression and genomic stability

“…7) may suggest that these chaperones link PCNA both to nucleosome deposition and activation of TLS polymerases through PCNA ubiquitylation by the RAD6/RAD18 pathway. Notably, these results are in agreement with the involvement of CAC1 in the RAD6/18 post-replication repair pathway [32].…”

“…These results are in agreement with previous studies [30][31][32] and deepen our understanding about the importance of Caf1 subunits on DNA replication under stress conditions.…”

“…Previous studies have revealed the contribution of the Caf1 subunits for H3/H4 assembly and nucleosome deposition under DNA stress conditions [30][31][32]. To further investigate the effect of cac2-or cac3-deletion on DNA replication under these conditions, we incubated the Caf1 mutant strains with 20 mM HU and measured their replication times as described above.…”

Dimerization of the largest subunit of chromatin assembly factor 1: importance in vitro and during Xenopus early development

“…Surprisingly, deletion of the genes encoding the three orthologous subunits in Saccharomyces cerevisae is not lethal and results in an increased sensitivity to UV irradiation and defects in transcriptional silencing in heterochromatic loci (Enomoto et al ., 1997; Kaufman et al ., 1997; Monson et al ., 1997; Enomoto and Berman, 1998; Game and Kaufman, 1999). Based on these data, it is possible that in S.cerevisiae , CAF‐1 is required predominantly for specialized functions associated with DNA repair of UV lesions and for maintenance of heterochromatic regions.…”

RebL1 is required for macronuclear structure stability and gametogenesis in Tetrahymena thermophila

“…In Drosophila , the removal of p55 affects the expression level of E2F-regulated genes (Taylor-Harding et al 2004 ). In yeast, Cac3/RBBP4 deletion decreases the silencing of telomeric genes and increases their lethality to ultraviolet radiation (Game and Kaufman 1999 ). In CD4 + T cell line, RBBP4 knockdown promotes HIV infection and virus particle generation (Wang et al 2016 ).…”