Biology subjects

Mazouzi, A.

Publications and source records attributed to Mazouzi, A..

3 recordsLinked to original sources

bioRxiv2025

Identification of critical factors of the replication stress response in human cells

High fidelity of replication is important to preserve genomic integrity and ensure healthy progeny. Perturbations of replication, also known as replication stress, is frequently observed in cancer cells and is considered a cancer cell-specific trait. Although replication stress drives genomic instability and tumor progression, it also generates a targetable cancer-specific vulnerability. In order to identify potential therapeutic targets in cancer cells that experience replication stress, we performed a genome wide genetic screen in human HAP1 cells challenged with low doses of replication stress-inducing drugs. We identified a large set of genes that specifically hamper cell survival in the context of replication stress. In addition to well-known players in the replication stress response and DNA repair, such as RNASEH1, BRIP1, and MDC1, we identified several genes with no prior described role in DNA replication, damage tolerance or repair. We validated that the loss of GIGYF2, HNRNPA2B1, and SUMO2 renders cells more vulnerable to replication stress. For GIGYF2 and SUMO2, we could implicate a role in homologous recombination. Taken together, our replication stress screen identified several known as well as some novel factors that protect against the toxic implications of replication stress. These factors could entail potential therapeutic targets for cancer cells experiencing replication stress.

cell biology↗

bioRxiv2024

Chromatin protein complexes involved in gene repression in lamina-associated domains

Lamina-associated domains (LADs) are large chromatin regions that are associated with the nuclear lamina (NL) and form a repressive environment for transcription. The molecular players that mediate gene repression in LADs are currently unknown. Here we performed FACS-based whole-genome genetic screens in human cells using LAD-integrated fluorescent reporters to identify such regulators. Surprisingly, the screen identified very few NL proteins, but revealed roles for dozens of known chromatin regulators. Among these are the negative elongation factor (NELF) complex and interacting factors involved in RNA polymerase pausing, suggesting that regulation of transcription elongation is a mechanism to repress transcription in LADs. Furthermore, the chromatin remodeler complex BAF and the activation complex Mediator can work both as activators and repressors in LADs, depending on the local context and possibly rewiring of heterochromatin. Our data clearly emphasize that the fundamental regulatory steps of the transcription process and chromatin remodeling factors, rather than interaction with NL proteins, play a major role in the regulation of transcription within LADs. HIGHLIGHTSO_LIHaploid genetic screens identify proteins that control gene activity in LADs C_LIO_LIChromatin proteins rather than NL proteins control repression in LADs C_LIO_LIRegulators of elongation contribute to repression of transcription in LADs C_LIO_LIBAF and Mediator can both repress and activate transcription in LADs C_LI

molecular biology↗

bioRxiv2024

Condensin II activation by M18BP1

Condensin complexes promote the drastic spatial rearrangement of the genome upon mitotic entry. Condensin II initiates chromosome condensation in early mitosis. To prevent chromosome condensation during interphase, condensin II is inhibited by MCPH1, but the mechanism is unknown. Through genetic and proteomic approaches, we identify M18BP1, a protein previously associated with centromere identity, as a factor required for condensin II localization to chromatin. M18BP1 directly binds condensin IIs CAP-G2 subunit and competes with MCPH1 for binding. Upon mitotic entry, CDK1 mediated phosphorylation may promote a switch from MCPH1 to M18BP1 binding to activate condensin II. Our results identify a fundamental and evolutionarily conserved mechanism of condensin II activation.

cell biology↗