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Xrs2 Dependent and Independent Functions of the Mre11-Rad50 Complex.

ABSTRACT: The Mre11-Rad50-Xrs2/Nbs1 (MRX/N) complex orchestrates the cellular response to DSBs through its structural, enzymatic, and signaling roles. Xrs2/Nbs1 is essential for nuclear translocation of Mre11, but its role as a component of the complex is not well defined. Here, we demonstrate that nuclear localization of Mre11 (Mre11-NLS) is able to bypass several functions of Xrs2, including DNA end resection, meiosis, hairpin resolution, and cellular resistance to clastogens. Using purified components, we show that the MR complex has equivalent activity to MRX in cleavage of protein-blocked DNA ends. Although Xrs2 physically interacts with Sae2, we found that end resection in its absence remains Sae2 dependent in vivo and in vitro. MRE11-NLS was unable to rescue the xrs2? defects in Tel1/ATM kinase signaling and non-homologous end joining, consistent with the role of Xrs2 as a chaperone and adaptor protein coordinating interactions between the MR complex and other repair proteins.

SUBMITTER: Oh J

PROVIDER: S-EPMC5123801 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Xrs2 Dependent and Independent Functions of the Mre11-Rad50 Complex.

Oh Julyun J Al-Zain Amr A Cannavo Elda E Cejka Petr P Symington Lorraine S LS

Molecular cell 20161013 2

The Mre11-Rad50-Xrs2/Nbs1 (MRX/N) complex orchestrates the cellular response to DSBs through its structural, enzymatic, and signaling roles. Xrs2/Nbs1 is essential for nuclear translocation of Mre11, but its role as a component of the complex is not well defined. Here, we demonstrate that nuclear localization of Mre11 (Mre11-NLS) is able to bypass several functions of Xrs2, including DNA end resection, meiosis, hairpin resolution, and cellular resistance to clastogens. Using purified components, ...[more]

PMID: 27746018

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The Mre11-Rad50-Xrs2 complex is required for yeast DNA postreplication repair.

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Gene Expression Profile of Deletion RAD50, MRE11, XRS2

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A Role for the Mre11-Rad50-Xrs2 Complex in Gene Expression and Chromosome Organization.

Project description:Mre11-Rad50-Xrs2 (MRX) is a highly conserved complex with key roles in various aspects of DNA repair. Here, we report a new function for MRX in limiting transcription in budding yeast. We show that MRX interacts physically and colocalizes on chromatin with the transcriptional co-regulator Mediator. MRX restricts transcription of coding and noncoding DNA by a mechanism that does not require the nuclease activity of Mre11. MRX is required to tether transcriptionally active loci to the nuclear pore complex (NPC), and it also promotes large-scale gene-NPC interactions. Moreover, MRX-mediated chromatin anchoring to the NPC contributes to chromosome folding and helps to control gene expression. Together, these findings indicate that MRX has a role in transcription and chromosome organization that is distinct from its known function in DNA repair.

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S. cerevisiae Mre11 recruits conjugated SUMO moieties to facilitate the assembly and function of the Mre11-Rad50-Xrs2 complex.

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Sae2 is an endonuclease that processes hairpin DNA cooperatively with the Mre11/Rad50/Xrs2 complex.

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Gene Expression Profile of Deletion RAD50, MRE11, XRS2

Project description:Deletion mutants of the yeast MRX complex (Rad50, Mre11 and Xrs2) were studied for gene expression levels. Significant difference in expression levels was observed in genes pertaining to DNA damage, cell cycle etc. as compared to the BY4741 wild type. Organism : Saccharomyces cerevisiae , Custom Saccharomyces cerevisiae 8x15k Gene expresssion Microarray (AMADID: 016333) designed by Genotypic Technology Private Limited

2015-12-31 | E-GEOD-48538 | biostudies-arrayexpress

A role for the Mre11–Rad50–Xrs2 complex in gene expression and chromosome organization

Project description:Mre11–Rad50–Xrs2 (MRX) is a highly conserved complex with key roles in various aspects of DNA repair. Here, we report a new function for MRX in limiting transcription in budding yeast. We show that MRX interacts physically and colocalizes on chromatin with the transcriptional co-regulator Mediator. It restricts transcription of coding and noncoding DNA independently by a mechanism that does not require the nuclease activity of Mre11. MRX is required to tether the active GAL locus to the nuclear pore complex (NPC) and also promotes large-scale gene–NPC interactions. Moreover, MRX-mediated chromatin anchoring to the NPC contributes to chromosome folding and helps to control gene expression. Together, these findings indicate that MRX has a role in transcription and chromosome organization that is distinct from its known function in DNA repair.

2020-12-01 | GSE148170 | GEO

Physiological protein blocks direct the Mre11-Rad50-Xrs2 and Sae2 nuclease complex to initiate DNA end resection.

Project description:DNA double-strand break repair by homologous recombination is initiated by DNA end resection, which is commenced by the Mre11-Rad50-Xrs2 complex and Sae2 in yeast. Here we report that the nonhomologous end joining factor Ku limits the exonuclease activity of Mre11 and promotes its endonuclease to cleave 5'-terminated DNA strands at break sites. Following initial endonucleolytic cleavage past the obstacle, Exo1 specifically extends the resection track, leading to the generation of long 3' overhangs that are required for homologous recombination. These experiments provide mechanistic insights into how short-range and long-range DNA end resection enzymes overcome obstacles near broken DNA ends to initiate recombination.

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MRE11-RAD50-NBS1 complex dictates DNA repair independent of H2AX.

Project description:DNA double-strand breaks (DSBs) represent one of the most serious forms of DNA damage that can occur in the genome. Here, we show that the DSB-induced signaling cascade and homologous recombination (HR)-mediated DSB repair pathway can be genetically separated. We demonstrate that the MRE11-RAD50-NBS1 (MRN) complex acts to promote DNA end resection and the generation of single-stranded DNA, which is critically important for HR repair. These functions of the MRN complex can occur independently of the H2AX-mediated DNA damage signaling cascade, which promotes stable accumulation of other signaling and repair proteins such as 53BP1 and BRCA1 to sites of DNA damage. Nevertheless, mild defects in HR repair are observed in H2AX-deficient cells, suggesting that the H2AX-dependent DNA damage-signaling cascade assists DNA repair. We propose that the MRN complex is responsible for the initial recognition of DSBs and works together with both CtIP and the H2AX-dependent DNA damage-signaling cascade to facilitate repair by HR and regulate DNA damage checkpoints.

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Sae2 promotes DNA damage resistance by removing the Mre11-Rad50-Xrs2 complex from DNA and attenuating Rad53 signaling.

Project description:The Mre11-Rad50-Xrs2/NBS1 (MRX/N) nuclease/ATPase complex plays structural and catalytic roles in the repair of DNA double-strand breaks (DSBs) and is the DNA damage sensor for Tel1/ATM kinase activation. Saccharomyces cerevisiae Sae2 can function with MRX to initiate 5'-3' end resection and also plays an important role in attenuation of DNA damage signaling. Here we describe a class of mre11 alleles that suppresses the DNA damage sensitivity of sae2? cells by accelerating turnover of Mre11 at DNA ends, shutting off the DNA damage checkpoint and allowing cell cycle progression. The mre11 alleles do not suppress the end resection or hairpin-opening defects of the sae2? mutant, indicating that these functions of Sae2 are not responsible for DNA damage resistance. The purified M(P110L)RX complex shows reduced binding to single- and double-stranded DNA in vitro relative to wild-type MRX, consistent with the increased turnover of Mre11 from damaged sites in vivo. Furthermore, overproduction of Mre11 causes DNA damage sensitivity only in the absence of Sae2. Together, these data suggest that it is the failure to remove Mre11 from DNA ends and attenuate Rad53 kinase signaling that causes hypersensitivity of sae2? cells to clastogens.

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