Biology subjects

Bagci, H.

Publications and source records attributed to Bagci, H..

5 recordsLinked to original sources

bioRxiv2023

The hGID GID4 E3 ubiquitin ligase complex targets ARHGAP11A to regulate cell migration

The human CTLH/GID (hGID) complex emerged as an important E3 ligase regulating multiple cellular processes, including cell cycle progression and metabolic activity. However, the range of biological functions controlled by hGID remains unexplored. Here, we show that the hGID substrate receptor GID4 regulates cell growth and migration. Biochemical and cellular assays combined with proximity-dependent biotinylation (BioID2) revealed that the hGIDGID4 E3-ligase targets the Rho-GAP ARHGAP11A for degradation. Depletion of GID4 or impeding the GID4 substrate binding pocket impairs motility and directed cell movement, whereas knockdown of ARHGAP11A significantly restores the cell migration defect. We found that GID4 controls cell migration by degrading ARHGAP11A thereby preventing its accumulation at the cell periphery where it inactivates RhoA activity. Together, we identified a unique function for GID4, as well as a wide range of substrate profiles beyond Pro/N-degron motifs, which pave the way for deciphering additional pathways regulated by hGID E3 ligase activity through its GID4 substrate receptor.

biochemistry↗

bioRxiv2021

POGZ modulates the DNA damage response in a HP1-dependent manner

The heterochromatin protein HP1 plays a central role in the maintenance of genome stability, in particular by promoting homologous recombination (HR)-mediated DNA repair. However, little is still known about how HP1 is controlled during this process. Here, we describe a novel function of the POGO transposable element derived with ZNF domain protein (POGZ) in the regulation of HP1 during the DNA damage response in vitro. POGZ depletion delays the resolution of DNA double-strand breaks (DSBs) and correlates with an increased sensitivity to different DNA damaging agents, including the clinically-relevant Cisplatin and Talazoparib. Mechanistically, POGZ promotes homology-directed DNA repair pathways by retaining the BRCA1/BARD1 complex at DSBs, in a HP1-dependent manner. In vivo CRISPR inactivation of Pogz is embryonically lethal and Pogz haplo-insufficiency (Pogz+/{Delta}) results in a developmental delay, impaired intellectual abilities, a hyperactive behaviour as well as a compromised humoral immune response in mice, recapitulating the main clinical features of the White Sutton syndrome (WHSUS). Importantly, Pogz+/{Delta} mice are radiosensitive and accumulate DSBs in diverse tissues, including the spleen and the brain. Altogether, our findings identify POGZ as an important player in homology-directed DNA repair both in vitro and in vivo, with clinical implications for the WHSUS.

molecular biology↗

bioRxiv2021

GFI1 tethers the NuRD complex to open and transcriptionally active chromatin in myeloid progenitors

GFI1 is a SNAG-domain, DNA binding transcriptional repressor which controls myeloid differentiation, in particular the formation of neutrophils. Here we show that GFI1 interacts with the chromodomain helicase CHD4 and other components of the "Nucleosome remodeling and deacetylase" (NuRD) complex. In granulo-monocytic precursors, GFI1, CHD4 or GFI1/CHD4 complexes occupy sites of open chromatin enriched for histone marks associated with active transcription suggesting that GFI1 recruits the NuRD complex to target genes that are regulated by active or bivalent promoters and active enhancers. Our data also show that GFI1 and GFI1/CHD4 complexes occupy promoters of different sets of genes that are either enriched for IRF1 or SPI-1 consensus sites, respectively. During neutrophil differentiation, overall chromatin closure and depletion of H3K4me2 occurs at different degrees depending on whether GFI1, CHD4 or both are present, indicating that GFI1 affects the chromatin remodeling activity of the NuRD complex. Moreover, GFI1/CHD4 complexes regulate chromatin openness and histone modifications differentially to enable regulation of target genes affecting the signaling pathways of the immune response or nucleosome organization or cellular metabolic processes.

molecular biology↗

bioRxiv2018

The endosomal sorting adaptor HD-PTP is required for ephrin-B:EphB signalling in cell collapse and motor axon guidance

The signalling output of many transmembrane receptors that mediate cell-cell communication is restricted by the endosomal sorting complex required for transport (ESCRT), but the impact of this machinery on Eph tyrosine kinase receptor function is unknown. We identified the ESCRT-associated adaptor protein HD-PTP as part of an EphB2 BioID interactome, and confirmed this association using co-immunoprecipitation. Although HD-PTP loss does not change EphB2 expression, it attenuates the ephrin-B2:EphB2 signalling-induced collapse of cultured cells and axonal growth cones, and results in aberrant guidance of chick spinal motor neuron axons in vivo HD-PTP depletion abrogates ligand-induced EphB2 clustering, and EphB2 and Src family kinase activation. HD-PTP deficiency also accelerates ligand-induced EphB2 degradation, contrasting the phenotypes reported for other cell surface receptors. Our results link Eph signalling to the ESCRT machinery and demonstrate a role for HD-PTP in the earliest steps of ephrin-B:EphB signalling, as well as in obstructing premature receptor depletion.

cell biology↗

bioRxiv2018

FAM35A co-operates with REV7 to coordinate DNA double-strand break repair pathway choice.

DNA double-strand breaks (DSBs) can be repaired by two major pathways: non-homologous end-joining (NHEJ) and homologous recombination (HR). DNA repair pathway choice is governed by the opposing activities of 53BP1, in complex with its effectors RIF1 and REV7, and BRCA1. However, it remains unknown how the 53BP1/RIF1/REV7 complex stimulates NHEJ and restricts HR to the S/G2 phases of the cell cycle. Using a mass spectrometry (MS)-based approach, we identify 11 high-confidence REV7 interactors and elucidate the role of a previously undescribed factor, FAM35A/SHDL2, as a novel effector of REV7 in the NHEJ pathway. FAM35A depletion impairs NHEJ-mediated DNA repair and compromises antibody diversification by class switch recombination (CSR) in B-cells. FAM35A accumulates at DSBs in a 53BP1-, RIF1- and REV7-dependent manner and antagonizes HR by limiting DNA end resection. In fact, FAM35A is part of a larger complex composed of REV7 and another previously uncharacterized protein, C20orf196/SHDL1, which promotes NHEJ and limits HR. Together, these results establish FAM35A as a novel effector of REV7 in controlling the decision-making process during DSB repair.

cancer biology↗