Multifaceted roles of H2B mono-ubiquitylation in D-loop metabolism during homologous recombination repair.

Unlabelled: Repairing DNA double-strand breaks is crucial for maintaining genome integrity, which occurs primarily through homologous recombination (HR) in Nucleosomes, composed of DNA wrapped around a histone octamer, present a natural barrier to end-resection to initiate HR, but the impact on the downstream HR steps of homology search, DNA strand invasion and repair synthesis remain to be determined. Displacement loops (D-loops) play a pivotal role in HR, yet the influence of chromatin dynamics on D-loop metabolism remains unclear. Using the physical D-loop capture (DLC) and D-loop extension (DLE) assays to track HR intermediates, we employed genetic analysis to reveal that H2B mono-ubiquitylation (H2Bubi) affects multiple steps during HR repair.

Rad51 determines pathway usage in post-replication repair.

Stalled replication forks can be processed by several distinct mechanisms collectively called post-replication repair which includes homologous recombination, fork regression, and translesion DNA synthesis. However, the regulation of the usage between these pathways is not fully understood. The Rad51 protein plays a pivotal role in maintaining genomic stability through its roles in HR and in protecting stalled replication forks from degradation.

Multi-step control of homologous recombination via Mec1/ATR suppresses chromosomal rearrangements.

The Mec1/ATR kinase is crucial for genome stability, yet the mechanism by which it prevents gross chromosomal rearrangements (GCRs) remains unknown. Here we find that in cells with deficient Mec1 signaling, GCRs accumulate due to the deregulation of multiple steps in homologous recombination (HR). Mec1 primarily suppresses GCRs through its role in activating the canonical checkpoint kinase Rad53, which ensures the proper control of DNA end resection.

Local structural dynamics of Rad51 protomers revealed by cryo-electron microscopy of Rad51-ssDNA filaments.

Homologous recombination (HR) is a high-fidelity repair mechanism for double-strand breaks. Rad51 is the key enzyme that forms filaments on single-stranded DNA (ssDNA) to catalyze homology search and DNA strand exchange in recombinational DNA repair. In this study, we employed single-particle cryo-electron microscopy (cryo-EM) to ascertain the density map of the budding yeast Rad51-ssDNA filament bound to ADP-AlF , achieving a resolution of 2.

Multi-Step Control of Homologous Recombination by Mec1/ATR Ensures Robust Suppression of Gross Chromosomal Rearrangements.

The Mec1/ATR kinase is crucial for genome stability, yet the mechanism by which it prevents gross chromosomal rearrangements (GCRs) remains unknown. Here we find that in cells with deficient Mec1 signaling, GCRs accumulate due to the deregulation of multiple steps in homologous recombination (HR). Mec1 primarily suppresses GCRs through its role in activating the canonical checkpoint kinase Rad53, which ensures the proper control of DNA end resection.