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Accumulation of sumoylated Rad52 in checkpoint mutants perturbed in DNA replication

ABSTRACT: Checkpoints are cellular surveillance and signaling pathways that regulate responses to DNA damage and perturbations of DNA replication. Here we show that high levels of sumoylated Rad52 are present in the mec1 sml1 and rad53 sml1 checkpoint mutants exposed to DNA damaging agents such as methyl methanesulfonate (MMS) or the DNA replication inhibitor hydroxyurea (HU). The kinase-defective mutant rad53-K227A also showed high levels of Rad52 sumoylation. Elevated levels of Rad52 sumoylation occur in checkpoint mutants proceeding S phase being exposed DNA-damaging agent. Interestingly, ChIP on chip analyses revealed non-canonical chromosomal localization of Rad52 in the HU-treated rad53-K227A cells arrested in early S phase: Rad52 localization at dormant and early DNA replication origins. However, such unusual localization was not dependent on the sumoylation of Rad52. In addition, we also found that Rad52 could be highly sumoylated in the absence of Rad51. Double deletion of RAD51 and RAD53 exhibited the similar levels of Rad52 sumoylation to RAD51 single deletion. The significance and regulation mechanism of Rad52 sumoylation by checkpoint pathways will be discussed. Keywords: ChIP-chip

ORGANISM(S): Saccharomyces cerevisiae

PROVIDER: GSE14761 | GEO | 2009/05/26

SECONDARY ACCESSION(S): PRJNA112255

REPOSITORIES: GEO

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Project description:Checkpoints are cellular surveillance and signaling pathways that regulate responses to DNA damage and perturbations of DNA replication. Here we show that high levels of sumoylated Rad52 are present in the mec1 sml1 and rad53 sml1 checkpoint mutants exposed to DNA damaging agents such as methyl methanesulfonate (MMS) or the DNA replication inhibitor hydroxyurea (HU). The kinase-defective mutant rad53-K227A also showed high levels of Rad52 sumoylation. Elevated levels of Rad52 sumoylation occur in checkpoint mutants proceeding S phase being exposed DNA-damaging agent. Interestingly, ChIP on chip analyses revealed non-canonical chromosomal localization of Rad52 in the HU-treated rad53-K227A cells arrested in early S phase: Rad52 localization at dormant and early DNA replication origins. However, such unusual localization was not dependent on the sumoylation of Rad52. In addition, we also found that Rad52 could be highly sumoylated in the absence of Rad51. Double deletion of RAD51 and RAD53 exhibited the similar levels of Rad52 sumoylation to RAD51 single deletion. The significance and regulation mechanism of Rad52 sumoylation by checkpoint pathways will be discussed. Keywords: ChIP-chip â¢ The goal of the experiment Genome-wide localization of Rad52 binding sites in Saccharomyces cerevisiae â¢ Experimental factor Distribution of Rad52 on chromosome III, IV, and V and the right arm of chromosome VI Strain: wild type, rad53 mutant, and rad53 siz2 mutant (W303 background, expressing myc tagged protein from its native promoter) Cell condition 1: G1 arrest with alpha-factor Cell condition 2: HU treatment â¢ Experimental design ChIP analyses: ChIP using anti-c-Myc antibody. ChIP-chip analyses: In all cases, hybridization data of ChIP fraction was compared with WCE (whole cell extract) fraction. Saccharomyces cerevisiae affymetrix genome tiling array (SC3456a520015F) were used. â¢ Quality control steps taken Confirmation of several loci by quantitative real time PCR. Wild type cells expressing non-tagged Rad52 were used as a negative control of DNA amplification.

Project description:Chromosomal DNA replication involves the coordinated activity of hundreds to thousands of replication origins. Individual replication origins are subject to epigenetic regulation of their activity during S-phase, resulting in differential efficiencies and timings of replication initiation during S-phase. This regulation is thought to involve chromatin structure and organization into timing domains with differential ability to recruit limiting replication factors. Rif1 has recently been identified as a genome-wide regulator of replication timing in fission yeast and in mammalian cells. However, previous studies in budding yeast have suggested that Rif1’s role in controlling replication timing may be limited to subtelomeric domains and derives from its established role in telomere length regulation. We have analyzed replication timing by analyzing BrdU incorporation genome-wide, and report that Rif1 regulates the timing of late/dormant replication origins throughout the S. cerevisiae genome. Analysis of pfa4∆ cells, which are defective in palmitoylation and membrane association of Rif1, suggests that replication timing regulation by Rif1 is independent of its role in localizing telomeres to the nuclear periphery. Intra-S checkpoint signaling is intact in rif1∆ cells, and checkpoint-defective mec1∆ cells do not comparably deregulate replication timing, together indicating that Rif1 regulates replication timing through a mechanism independent of this checkpoint. Our results indicate that the Rif1 mechanism regulates origin timing irrespective of proximity to a chromosome end, and suggest instead that telomere sequences merely provide abundant binding sites for proteins that recruit Rif1. Still, the abundance of Rif1 binding in telomeric domains may facilitate Rif1-mediated repression of non-telomeric origins that are more distal from centromeres. 30 total samples: (6 samples - BrdU- HU arrest 45min with 2 replicates, strains: WT, rif1 delta, pfa4 delta) (12 samples -S-phase BrdU time course with 2 replicates at 25 and 35 min, strains: WT, rif1 delta, mec1_100) (12 samples - S-phase BrdU time course with 2 replicates at 25 and 35 min, strains: sml1 delta, sml1 delta rif1 delta, sml1 delta mec1 delta)

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Accumulation of sumoylated Rad52 in checkpoint mutants perturbed in DNA replication

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