Misrejoining of DNA double-strand breaks in primary and transformed human and rodent cells: a comparison between the HPRT region and other genomic locations

Abstract In most taxa, halving of chromosome numbers during meiosis requires that homologous chromosomes (homologues) pair and form crossovers. Crossovers emerge from the recombination-mediated repair of programmed DNA double-strand breaks (DSBs). DSBs are generated by SPO11, whose activity requires auxiliary protein complexes, called pre-DSB recombinosomes. To elucidate the spatiotemporal control of the DSB machinery, we focused on an essential SPO11 auxiliary protein, IHO1, which serves as the main anchor for pre-DSB recombinosomes on chromosome cores, called axes. We discovered that DSBs restrict the DSB machinery by at least four distinct pathways in mice. Firstly, by activating the DNA damage response (DDR) kinase ATM, DSBs restrict pre-DSB recombinosome numbers without affecting IHO1. Secondly, in their vicinity, DSBs trigger IHO1 depletion mainly by another DDR kinase, ATR. Thirdly, DSBs enable homologue synapsis, which promotes the depletion of IHO1 and pre-DSB recombinosomes from synapsed axes. Finally, DSBs and three DDR kinases, ATM, ATR and PRKDC, enable stage-specific depletion of IHO1 from all axes. We hypothesize that these four negative feedback pathways protect genome integrity by ensuring that DSBs form without excess, are well-distributed, and are restricted to genomic locations and prophase stages where DSBs are functional for promoting homologue pairing and crossover formation.

Download Full-text

Genetic Interactions of Histone Modification Machinery Set1 and PAF1C with the Recombination Complex Rec114-Mer2-Mei4 in the Formation of Meiotic DNA Double-Strand Breaks

International Journal of Molecular Sciences ◽

10.3390/ijms21082679 ◽

2020 ◽

Vol 21 (8) ◽

pp. 2679

Author(s):

Ying Zhang ◽

Takuya Suzuki ◽

Ke Li ◽

Santosh K. Gothwal ◽

Miki Shinohara ◽

...

Keyword(s):

Histone Modification ◽

Genetic Interaction ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

H3k4 Methylation ◽

Yeast Saccharomyces Cerevisiae ◽

Strand Breaks ◽

Histone H3k4 ◽

Genomic Locations ◽

Chromosome Axis

Homologous recombination is essential for chromosome segregation during meiosis I. Meiotic recombination is initiated by the introduction of double-strand breaks (DSBs) at specific genomic locations called hotspots, which are catalyzed by Spo11 and its partners. DSB hotspots during meiosis are marked with Set1-mediated histone H3K4 methylation. The Spo11 partner complex, Rec114-Mer2-Mei4, essential for the DSB formation, localizes to the chromosome axes. For efficient DSB formation, a hotspot with histone H3K4 methylation on the chromatin loops is tethered to the chromosome axis through the H3K4 methylation reader protein, Spp1, on the axes, which interacts with Mer2. In this study, we found genetic interaction of mutants in a histone modification protein complex called PAF1C with the REC114 and MER2 in the DSB formation in budding yeast Saccharomyces cerevisiae. Namely, the paf1c mutations rtf1 and cdc73 showed synthetic defects in meiotic DSB formation only when combined with a wild-type-like tagged allele of either the REC114 or MER2. The synthetic defect of the tagged REC114 allele in the DSB formation was seen also with the set1, but not with spp1 deletion. These results suggest a novel role of histone modification machinery in DSB formation during meiosis, which is independent of Spp1-mediated loop-axis tethering.

Download Full-text

Identification of a signature of evolutionarily conserved stress-induced mutagenesis in cancer

10.1101/2021.04.17.440291 ◽

2021 ◽

Author(s):

Luis Humberto Cisneros ◽

Kimberly J Bussey ◽

Charles Vasque

Keyword(s):

Double Strand Breaks ◽

Whole Genome Sequencing Data ◽

Dna Double Strand Breaks ◽

Sequencing Data ◽

Single Nucleotide ◽

Strand Breaks ◽

Evolutionarily Conserved ◽

Induced Mutagenesis ◽

Genomic Locations ◽

Inherited Mutations

The clustering of mutations observed in cancer cells is reminiscent of the stress-induced mutagenesis (SIM) response in bacteria. SIM employs error-prone polymerases resulting in mutations concentrated around DNA double-strand breaks with an abundance that decays with genomic distance. We performed a quantitative study on single nucleotide variant calls for whole-genome sequencing data from 1950 tumors and non-inherited mutations from 129 normal samples. We introduce statistical methods to identify mutational clusters and quantify their distribution pattern. Our results show that mutations in both normal and cancer samples are indeed clustered and have shapes indicative of SIM. We found the genomic locations of groups of close mutations are more likely to be prevalent across normal samples than in cancer suggesting loss of regulation over the mutational process during carcinogenesis.

Download Full-text

PRDM9 activity depends on HELLS and promotes local 5-hydroxymethylcytosine enrichment

eLife ◽

10.7554/elife.57117 ◽

2020 ◽

Vol 9 ◽

Author(s):

Yukiko Imai ◽

Mathilde Biot ◽

Julie AJ Clément ◽

Mariko Teragaki ◽

Serge Urbach ◽

...

Keyword(s):

Binding Sites ◽

Male Meiosis ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Chromatin Remodelers ◽

Strand Breaks ◽

Complex Regulation ◽

Genomic Locations ◽

Functional Analyses ◽

Deficient Mice

Meiotic recombination starts with the formation of DNA double-strand breaks (DSBs) at specific genomic locations that correspond to PRDM9-binding sites. The molecular steps occurring from PRDM9 binding to DSB formation are unknown. Using proteomic approaches to find PRDM9 partners, we identified HELLS, a member of the SNF2-like family of chromatin remodelers. Upon functional analyses during mouse male meiosis, we demonstrated that HELLS is required for PRDM9 binding and DSB activity at PRDM9 sites. However, HELLS is not required for DSB activity at PRDM9-independent sites. HELLS is also essential for 5-hydroxymethylcytosine (5hmC) enrichment at PRDM9 sites. Analyses of 5hmC in mice deficient for SPO11, which catalyzes DSB formation, and in PRDM9 methyltransferase deficient mice reveal that 5hmC is triggered at DSB-prone sites upon PRDM9 binding and histone modification, but independent of DSB activity. These findings highlight the complex regulation of the chromatin and epigenetic environments at PRDM9-specified hotspots.

Download Full-text

Repair pathway choice for double-strand breaks

Essays in Biochemistry ◽

10.1042/ebc20200007 ◽

2020 ◽

Vol 64 (5) ◽

pp. 765-777 ◽

Cited By ~ 2

Author(s):

Yixi Xu ◽

Dongyi Xu

Keyword(s):

Cell Cycle ◽

Double Strand Breaks ◽

Homologous Region ◽

Gene Repair ◽

Repair Pathway ◽

Dna Double Strand Breaks ◽

Environmental Radiation ◽

Strand Breaks ◽

Dna End Resection ◽

End Resection

Abstract Deoxyribonucleic acid (DNA) is at a constant risk of damage from endogenous substances, environmental radiation, and chemical stressors. DNA double-strand breaks (DSBs) pose a significant threat to genomic integrity and cell survival. There are two major pathways for DSB repair: nonhomologous end-joining (NHEJ) and homologous recombination (HR). The extent of DNA end resection, which determines the length of the 3′ single-stranded DNA (ssDNA) overhang, is the primary factor that determines whether repair is carried out via NHEJ or HR. NHEJ, which does not require a 3′ ssDNA tail, occurs throughout the cell cycle. 53BP1 and the cofactors PTIP or RIF1-shieldin protect the broken DNA end, inhibit long-range end resection and thus promote NHEJ. In contrast, HR mainly occurs during the S/G2 phase and requires DNA end processing to create a 3′ tail that can invade a homologous region, ensuring faithful gene repair. BRCA1 and the cofactors CtIP, EXO1, BLM/DNA2, and the MRE11–RAD50–NBS1 (MRN) complex promote DNA end resection and thus HR. DNA resection is influenced by the cell cycle, the chromatin environment, and the complexity of the DNA end break. Herein, we summarize the key factors involved in repair pathway selection for DSBs and discuss recent related publications.

Download Full-text