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Non-recombinogenic roles for Rad52 in translesion synthesis during DNA damage tolerance.

ABSTRACT: DNA damage tolerance relies on homologous recombination (HR) and translesion synthesis (TLS) mechanisms to fill in the ssDNA gaps generated during passing of the replication fork over DNA lesions in the template. Whereas TLS requires specialized polymerases able to incorporate a dNTP opposite the lesion and is error-prone, HR uses the sister chromatid and is mostly error-free. We report that the HR protein Rad52-but not Rad51 and Rad57-acts in concert with the TLS machinery (Rad6/Rad18-mediated PCNA ubiquitylation and polymerases Rev1/Pol ζ) to repair MMS and UV light-induced ssDNA gaps through a non-recombinogenic mechanism, as inferred from the different phenotypes displayed in the absence of Rad52 and Rad54 (essential for MMS- and UV-induced HR); accordingly, Rad52 is required for efficient DNA damage-induced mutagenesis. In addition, Rad52, Rad51, and Rad57, but not Rad54, facilitate Rad6/Rad18 binding to chromatin and subsequent DNA damage-induced PCNA ubiquitylation. Therefore, Rad52 facilitates the tolerance process not only by HR but also by TLS through Rad51/Rad57-dependent and -independent processes, providing a novel role for the recombination proteins in maintaining genome integrity.

SUBMITTER: Cano-Linares MI

PROVIDER: S-EPMC7788459 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Non-recombinogenic roles for Rad52 in translesion synthesis during DNA damage tolerance

Project description:DNA damage tolerance relies on homologous recombination (HR) and translesion synthesis (TLS) mechanisms to fill in the ssDNA gaps generated during passing of the replication fork over DNA lesions in the template. Whereas TLS requires specialized polymerases able to incorporate a dNTP opposite the lesion and is error-prone, HR uses the sister chromatid and is mostly error-free. We report that the HR protein Rad52 -but not Rad51 and Rad57- acts in concert with the TLS machinery (Rad6/Rad18-mediated PCNA ubiquitylation and polymerases Rev1/Pol ) to repair MMS and UV light-induced ssDNA gaps through a non-recombinogenic mechanism, as inferred from the different phenotypes displayed in the absence of Rad52 and Rad54 (essential for MMS- and UV-induced HR); accordingly, Rad52 is required for efficient DNA damage-induced mutagenesis. In addition, Rad52, Rad51 and Rad57, but not Rad54, facilitate Rad6/Rad18 binding to chromatin and subsequent DNA damage-induced PCNA ubiquitylation. Therefore, Rad52 facilitates the tolerance process not only by HR but also by TLS through Rad51/Rad57-dependent and independent processes, providing a novel role for the recombination proteins in maintaining genome integrity.

| S-SCDT-EMBOR-2020-50410V1 | biostudies-other

The NuA4 complex promotes Translesion Synthesis (TLS) - mediated DNA damage tolerance

Project description:DNA lesions can block a replication fork, leading to its collapse and gross chromosomal rearrangements. To circumvent such outcomes, DNA damage tolerance (DDT) pathways become engaged, allowing the replisome to bypass the lesion and complete S phase in the presence of unrepaired damage. Here we demonstrate a newly identified role for NuA4, including complex components Esa1 and Yng2, on the Translesion Synthesis (TLS) branch of DDT. Moreover, Our data suggest that NuA4 functionality within the tolerance pathway is likely direct as genome-wide transcriptional analysis with esa1-L254P mutants showed little changes in the expression of TLS factors compared to wild type during MMS treatment. When Yng2 expression is restricted to G2/M, cell viability and mutagenesis rates are restored to the levels measured when only the error-free branch of DDT is disrupted, indicating that the critical role of NuA4 in TLS functions in G2, after chromosomal replication is complete. Lastly, disruption of HTZ1, the Saccharomyces cerevisiae histone variant H2A.Z and target of NuA4, exhibits mutagenic rates of reversion that are comparable to the levels measured with NuA4 complex mutants, esa1-L254P and yng2M-NM-^T. The esa1-L254P strain was compared to wild type through a series of microarrays utilizing dye swaps with and without treatment of MMS. These included synchronized cells in G1 and S phase through alpha factor treatment. Four unique microarrays were performed each with dye swaps, comparing wild type to esa1-L254P in G1 and S phase with and without treatment with MMS. As a set of controls, four microarrays were performed comparing identical strains with and without MMS in G1 or S phase.

2015-02-21 | E-GEOD-66176 | biostudies-arrayexpress

The NuA4 complex promotes Translesion Synthesis (TLS) - mediated DNA damage tolerance

2015-02-21 | GSE66176 | GEO

The NuA4 complex promotes translesion synthesis (TLS)-mediated DNA damage tolerance.

Project description:Lesions in DNA can block replication fork progression, leading to its collapse and gross chromosomal rearrangements. To circumvent such outcomes, the DNA damage tolerance (DDT) pathway becomes engaged, allowing the replisome to bypass a lesion and complete S phase. Chromatin remodeling complexes have been implicated in the DDT pathways, and here we identify the NuA4 remodeler, which is a histone acetyltransferase, to function on the translesion synthesis (TLS) branch of DDT. Genetic analyses in Saccharomyces cerevisiae showed synergistic sensitivity to MMS when NuA4 alleles, esa1-L254P and yng2?, were combined with the error-free bypass mutant ubc13?. The loss of viability was less pronounced when NuA4 complex mutants were disrupted in combination with error-prone/TLS factors, such as rev3?, suggesting an epistatic relationship between NuA4 and error-prone bypass. Consistent with cellular viability measurements, replication profiles after exposure to MMS indicated that small regions of unreplicated DNA or damage were present to a greater extent in esa1-L254P/ubc13? mutants, which persist beyond the completion of bulk replication compared to esa1-L254P/rev3?. The critical role of NuA4 in error-prone bypass is functional even after the bulk of replication is complete. Underscoring this observation, when Yng2 expression is restricted specifically to G2/M of the cell cycle, viability and TLS-dependent mutagenesis rates were restored. Lastly, disruption of HTZ1, which is a target of NuA4, also resulted in mutagenic rates of reversion on level with esa1-L254P and yng2? mutants, indicating that the histone variant H2A.Z functions in vivo on the TLS branch of DDT.

| S-EPMC4391564 | biostudies-literature

Identification of novel DNA-damage tolerance genes reveals regulation of translesion DNA synthesis by nucleophosmin.

Project description:Cells cope with replication-blocking lesions via translesion DNA synthesis (TLS). TLS is carried out by low-fidelity DNA polymerases that replicate across lesions, thereby preventing genome instability at the cost of increased point mutations. Here we perform a two-stage siRNA-based functional screen for mammalian TLS genes and identify 17 validated TLS genes. One of the genes, NPM1, is frequently mutated in acute myeloid leukaemia (AML). We show that NPM1 (nucleophosmin) regulates TLS via interaction with the catalytic core of DNA polymerase-? (pol?), and that NPM1 deficiency causes a TLS defect due to proteasomal degradation of pol?. Moreover, the prevalent NPM1c+ mutation that causes NPM1 mislocalization in ~30% of AML patients results in excessive degradation of pol?. These results establish the role of NPM1 as a key TLS regulator, and suggest a mechanism for the better prognosis of AML patients carrying mutations in NPM1.

| S-EPMC4263322 | biostudies-literature

Roles of exonucleases and translesion synthesis DNA polymerases during mitotic gap repair in yeast.

Project description:Transformation-based gap-repair assays have long been used to model the repair of mitotic double-strand breaks (DSBs) by homologous recombination in yeast. In the current study, we examine genetic requirements of two key processes involved in DSB repair: (1) the processive 5'-end resection that is required to efficiently engage a repair template and (2) the filling of resected ends by DNA polymerases. The specific gap-repair assay used allows repair events resolved as crossover versus noncrossover products to be distinguished, as well as the extent of heteroduplex DNA formed during recombination to be measured. To examine end resection, the efficiency and outcome of gap repair were monitored in the absence of the Exo1 exonuclease and the Sgs1 helicase. We found that either Exo1 or Sgs1 presence is sufficient to inhibit gap-repair efficiency over 10-fold, consistent with resection-mediated destruction of the introduced plasmid. In terms of DNA polymerase requirements for gap repair, we focused specifically on potential roles of the Pol ? and Pol ? translesion synthesis DNA polymerases. We found that both Pol ? and Pol ? are necessary for efficient gap repair and that each functions independently of the other. These polymerases may be involved either in the initiation of DNA synthesis from the an invading end, or in a gap-filling process that is required to complete recombination.

| S-EPMC3870910 | biostudies-literature

Genomic assay reveals tolerance of DNA damage by both translesion DNA synthesis and homology-dependent repair in mammalian cells.

Project description:DNA lesions can block replication forks and lead to the formation of single-stranded gaps. These replication complications are mitigated by DNA damage tolerance mechanisms, which prevent deleterious outcomes such as cell death, genomic instability, and carcinogenesis. The two main tolerance strategies are translesion DNA synthesis (TLS), in which low-fidelity DNA polymerases bypass the blocking lesion, and homology-dependent repair (HDR; postreplication repair), which is based on the homologous sister chromatid. Here we describe a unique high-resolution method for the simultaneous analysis of TLS and HDR across defined DNA lesions in mammalian genomes. The method is based on insertion of plasmids carrying defined site-specific DNA lesions into mammalian chromosomes, using phage integrase-mediated integration. Using this method we show that mammalian cells use HDR to tolerate DNA damage in their genome. Moreover, analysis of the tolerance of the UV light-induced 6-4 photoproduct, the tobacco smoke-induced benzo[a]pyrene-guanine adduct, and an artificial trimethylene insert shows that each of these three lesions is tolerated by both TLS and HDR. We also determined the specificity of nucleotide insertion opposite these lesions during TLS in human genomes. This unique method will be useful in elucidating the mechanism of DNA damage tolerance in mammalian chromosomes and their connection to pathological processes such as carcinogenesis.

| S-EPMC3631627 | biostudies-literature

PDIP38/PolDIP2 controls the DNA damage tolerance pathways by increasing the relative usage of translesion DNA synthesis over template switching.

Project description:Replicative DNA polymerases are frequently stalled at damaged template strands. Stalled replication forks are restored by the DNA damage tolerance (DDT) pathways, error-prone translesion DNA synthesis (TLS) to cope with excessive DNA damage, and error-free template switching (TS) by homologous DNA recombination. PDIP38 (Pol-delta interacting protein of 38 kDa), also called Pol ?-interacting protein 2 (PolDIP2), physically associates with TLS DNA polymerases, polymerase ? (Pol?), Pol?, and PrimPol, and activates them in vitro. It remains unclear whether PDIP38 promotes TLS in vivo, since no method allows for measuring individual TLS events in mammalian cells. We disrupted the PDIP38 gene, generating PDIP38-/- cells from the chicken DT40 and human TK6 B cell lines. These PDIP38-/- cells did not show a significant sensitivity to either UV or H2O2, a phenotype not seen in any TLS-polymerase-deficient DT40 or TK6 mutants. DT40 provides a unique opportunity of examining individual TLS and TS events by the nucleotide sequence analysis of the immunoglobulin variable (Ig V) gene as the cells continuously diversify Ig V by TLS (non-templated Ig V hypermutation) and TS (Ig gene conversion) during in vitro culture. PDIP38-/- cells showed a shift in Ig V diversification from TLS to TS. We measured the relative usage of TLS and TS in TK6 cells at a chemically synthesized UV damage (CPD) integrated into genomic DNA. The loss of PDIP38 also caused an increase in the relative usage of TS. The number of UV-induced sister chromatid exchanges, TS events associated with crossover, was increased a few times in PDIP38-/- human and chicken cells. Collectively, the loss of PDIP38 consistently causes a shift in DDT from TLS to TS without enhancing cellular sensitivity to DNA damage. We propose that PDIP38 controls the relative usage of TLS and TS increasing usage of TLS without changing the overall capability of DDT.

| S-EPMC6402704 | biostudies-literature

Homologous Recombination and Translesion DNA Synthesis Play Critical Roles on Tolerating DNA Damage Caused by Trace Levels of Hexavalent Chromium.

Project description:Contamination of potentially carcinogenic hexavalent chromium (Cr(VI)) in the drinking water is a major public health concern worldwide. However, little information is available regarding the biological effects of a nanomoler amount of Cr(VI). Here, we investigated the genotoxic effects of Cr(VI) at nanomoler levels and their repair pathways. We found that DNA damage response analyzed based on differential toxicity of isogenic cells deficient in various DNA repair proteins is observed after a three-day incubation with K2CrO4 in REV1-deficient DT40 cells at 19.2 ?g/L or higher as well as in TK6 cells deficient in polymerase delta subunit 3 (POLD3) at 9.8 ?g/L or higher. The genotoxicity of Cr(VI) decreased ~3000 times when the incubation time was reduced from three days to ten minutes. TK mutation rate also significantly decreased from 6 day to 1 day exposure to Cr(VI). The DNA damage response analysis suggest that DNA repair pathways, including the homologous recombination and REV1- and POLD3-mediated error-prone translesion synthesis pathways, are critical for the cells to tolerate to DNA damage caused by trace amount of Cr(VI).

| S-EPMC5132242 | biostudies-other

Translesion DNA Synthesis.

Project description:All living organisms are continually exposed to agents that damage their DNA, which threatens the integrity of their genome. As a consequence, cells are equipped with a plethora of DNA repair enzymes to remove the damaged DNA. Unfortunately, situations nevertheless arise where lesions persist, and these lesions block the progression of the cell's replicase. In these situations, cells are forced to choose between recombination-mediated "damage avoidance" pathways or a specialized DNA polymerase (pol) to traverse the blocking lesion. The latter process is referred to as Translesion DNA Synthesis (TLS). As inferred by its name, TLS not only results in bases being (mis)incorporated opposite DNA lesions but also bases being (mis)incorporated downstream of the replicase-blocking lesion, so as to ensure continued genome duplication and cell survival. Escherichia coli and Salmonella typhimurium possess five DNA polymerases, and while all have been shown to facilitate TLS under certain experimental conditions, it is clear that the LexA-regulated and damage-inducible pols II, IV, and V perform the vast majority of TLS under physiological conditions. Pol V can traverse a wide range of DNA lesions and performs the bulk of mutagenic TLS, whereas pol II and pol IV appear to be more specialized TLS polymerases.

| S-EPMC4231548 | biostudies-literature

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