Biology subjects

Starowicz, K.

Publications and source records attributed to Starowicz, K..

4 recordsLinked to original sources

bioRxiv2024

USP50 suppresses alternative RecQ helicase use and deleterious DNA2 activity during replication.

Mammalian DNA replication employs several RecQ DNA helicases to orchestrate the faithful duplication of genetic information. Helicase function is often coupled to the activity of specific nucleases, but how helicase and nuclease activities are co-directed is unclear. Here we identify the inactive ubiquitin-specific protease, USP50, as a ubiquitin-binding and chromatin-associated protein required for ongoing replication, fork restart, telomere maintenance and cellular survival during replicative stress. USP50 supports WRN:FEN1 at stalled replication forks, suppresses MUS81-dependent fork collapse and restricts double-strand DNA breaks at GC-rich sequences. Surprisingly we find that cells depleted for USP50 and recovering from a replication block exhibit increased DNA2 and RECQL4 foci and that the defects in ongoing replication, poor fork restart and increased fork collapse seen in these cells are mediated by DNA2, RECQL4 and RECQL5. These data define a novel ubiquitin-dependent pathway that promotes the balance of helicase: nuclease use at ongoing and stalled replication forks.

cancer biology↗

bioRxiv2022

RAD52 underlies the synthetic-lethal relationship between BRCA1/2 and 53BP1 deficiencies and DNA polymerase theta loss.

Introductory paragraphCells lacking several DNA repair proteins, including those promoting homologous recombination (HR), are sensitive to polymerase theta (Pol{theta}) repression1-4. Pol{theta} drives theta-mediated end joining (TMEJ) and suppresses HR but what mediates its synthetic lethal relationships is unclear. Here we examine murine Brca1C61G/C61G 53bp1-/-cells and find they are largely HR proficient by using RNF168 and RAD52. They exhibit no more TMEJ than 53bp1-/- cells yet are more sensitive to targeting of Pol{theta}. We find that RAD52 recruitment to damaged chromatin is increased following Pol{theta} depletion. RAD52 accumulation and cellular sensitivity to Pol{theta} repression can be curbed by the RAD51-binding regions of BARD1 and BRCA2, and sensitivity of BRCA1/2 depleted cells to Pol{theta} repression is suppressed by RAD52 inhibition. 53bp1-/- cells exhibit a smaller increase in RAD52 recruitment following Pol{theta} repression and also become resistant to Pol{theta} repression following RAD52 inhibition. Thus, RAD52 mediates sensitivity to targeting Pol{theta} in these contexts.

molecular biology↗

bioRxiv2018

The deSUMOylase SENP2 coordinates homologous recombination and non-homologous end joining by independent mechanisms.

SUMOylation in the DNA double-strand break (DSB) response regulates recruitment, activity and clearance of repair factors. However, our understanding of a role for deSUMOylation in this process is limited. Here we identify different mechanistic roles for deSUMOylation in homologous recombination (HR) and non-homologous enjoining (NHEJ) through the investigation of the deSUMOylase SENP2. We find regulated deSUMOylation of MDC1 prevents excessive SUMOylation and its RNF4-VCP mediated clearance from DSBs, thereby promoting NHEJ. In contrast we show HR is differentially sensitive to SUMO availability and SENP2 activity is needed to provide SUMO. SENP2 is amplified as part of the chromosome 3q amplification in many cancers. Increased SENP2 expression prolongs MDC1 foci retention and increases NHEJ and radioresistance. Collectively our data reveal that deSUMOylation differentially primes cells for responding to DSBs and demonstrates the ability of SENP2 to tune DSB repair responses.

cell biology↗

bioRxiv2018

PIN1 isomerisation of BRCA1 promotes replication fork protection.

BRCA1, BRCA2 and a subset of Fanconis Anaemia proteins act to promote RAD51-mediated protection of newly synthesised DNA at stalled replication forks from degradation by nucleases. How BRCA1 contributes, how it is regulated and whether replication fork protection relates to, or differs from, the roles BRCA1 has in homologous recombination is not clear. Here we show that the canonical BRCA1-PALB2 interaction is not required for fork protection and instead we demonstrate that the ability of BRCA1 to protect nascent DNA is regulated in an unexpected fashion through conformational change mediated by the phosphorylation-directed prolyl isomerase, PIN1. BRCA1 isomerisation enhances BRCA1-BARD1 interaction with RAD51 and consequently RAD51 presence at stalled replication structures. Our data suggest BRCA1-BARD1 promotes fork protection in part by enhancing the RAD51 synapse. Patient missense variants in the regulated BRCA1-BARD1 regions similarly show poor nascent strand protection but proficient homologous recombination, defining novel domains required for fork protection in BRCA1-BARD1 associated with cancer predisposition. Together these findings reveal a previously unrecognised pathway that governs BRCA1-mediated replication fork protection.

cell biology↗