Biology subjects

Shodhan, A.

Publications and source records attributed to Shodhan, A..

3 recordsLinked to original sources

bioRxiv2026

Directional branch migration remodels the meiotic Holliday junction landscape

Holliday junctions (HJs) are four-way branched DNA intermediates in double strand break (DSB) repair by homologous recombination. During meiosis, HJs are resolved predominantly as crossovers that are necessary for correct chromosome segregation. However, the genome-wide behavior of meiotic HJs has remained inaccessible without direct mapping. By a HJ-binding peptide approach (HJSeq), we capture the genome-wide distribution of these crucial intermediates for the first time. We show that during pachytene, the stage before crossover formation, HJs undergo sustained directional branch migration, reorganizing the HJ-landscape in a transcription-linked manner, away from DSB sites towards convergent transcription sites. The presented findings establish pachytene as an active remodeling phase in which HJ branch-migration accommodates an active chromatin environment to support regulated crossover formation and faithful chromosome segregation. HighlightsO_LIHJSeq enables genome-wide mapping of meiotic Holliday junctions C_LIO_LIHJ formation propensity is determined by DSB hotspot strength C_LIO_LIMeiotic HJs undergo long-range, transcription-linked branch migration C_LIO_LIDirectional HJ migration away from DSB sites is facilitated by the ZMM pathway C_LI

cell biology↗

bioRxiv2022

Turning coldspots into hotspots: targeted recruitment of axis protein Hop1 stimulates meiotic recombination in Saccharomyces cerevisiae

The DNA double strand breaks (DSBs) that initiate meiotic recombination are formed in the context of the meiotic chromosome axis, which in budding yeast contains a meiosis-specific cohesin isoform and the meiosis-specific proteins Hop1 and Red1. Hop1 and Red are important for DSB formation; DSB levels are reduced in their absence and their levels, which vary along the lengths of chromosomes, are positively correlated with DSB levels. How axis protein levels influence DSB formation and recombination remains unclear. To address this question, we developed a novel approach that uses a bacterial ParB-parS partition system to recruit axis proteins at high levels to inserts at recombination coldspots where Hop1 and Red1 levels are normally low. Recruiting Hop1 markedly increased DSBs and homologous recombination at target loci, to levels equivalent to those observed at endogenous recombination hotspots. This local increase in DSBs did not require Red1 or the meiosis-specific cohesin component Rec8, indicating that, of the axis proteins, Hop1 is sufficient to promote DSB formation. However, while most crossovers at endogenous recombination hotspots are formed by the meiosis-specific MutL{gamma} resolvase, only a small fraction of crossovers that formed at an insert locus required MutL{gamma}, regardless of whether or not Hop1 was recruited to that locus. Thus, while local Hop1 levels determine local DSB levels, the recombination pathways that repair these breaks can be determined by other factors, raising the intriguing possibility that different recombination pathways operate in different parts of the genome.

genetics↗

bioRxiv2019

Noncanonical contributions of MutLγ to VDE-initiated crossovers during Saccharomyces cerevisiae meiosis

In Saccharomyces cerevisiae, the meiosis-specific axis proteins Hop1 and Red1 are present nonuniformly across the genome. In a previous study, the meiosis-specific VMAl-derived endonuclease (VDE) was used to examine Spo11-independent recombination in a recombination reporter inserted in a Hop1/Red1-enriched region (HIS4) and in a Hop1/Red1-poor region (URA3). VDE-initiated crossovers at HIS4 were mostly dependent on Mlh3, a component of the MutL{gamma} meiotic recombination intermediate resolvase, while VDE-initiated crossovers at URA3 were mostly Mlh3-independent. These differences were abolished in the absence of the chromosome axis remodeler Pch2, and crossovers at both loci become partly Mlh3-dependent. To test the generality of these observations, we examined inserts at six additional loci that differed in terms of Hop1/Red1 enrichment, chromosome size, and distance from centromeres and telomeres. All six loci behaved similarly to URA3: the vast majority of VDE-initiated crossovers were Mlh3-independent. This indicates that, counter to previous suggestions, meiotic chromosome axis protein enrichment is not a primary determinant of which recombination pathway gives rise to crossovers during VDE-initiated meiotic recombination. In pch2{Delta} mutants, the fraction of VDE-induced crossovers that were Mlh3-dependent increased to levels previously observed for Spo11-initiated crossovers in pch2{Delta}, indicating that Pch2-dependent processes play an important role in controlling the distribution of factors necessary for MutL{gamma}-dependent crossovers.

genetics↗