Biology subjects

Garcia-Luis, J.

Publications and source records attributed to Garcia-Luis, J..

4 recordsLinked to original sources

bioRxiv2026

Human FACT complex coordinates cohesin and transcription on chromatin

The spatial organisation of eukaryotic genomes is critical for coordinating DNA-dependent processes such as transcription and replication. Cohesin contributes to this organisation by extruding chromatin loops; however, how cohesin achieves processive translocation along nucleosome-dense chromatin in vivo remains poorly understood. Here, we identify the histone chaperone FACT as a regulator of cohesin dynamics in human cells. We show that the FACT subunit SUPT16H colocalises and interacts with cohesin on chromatin. Depletion of FACT impairs cohesin translocation from its loading sites, leading to reduced chromatin looping and decreased boundary strength of topologically associating domains (TADs), as revealed by Hi-C. In addition, FACT depletion results in the accumulation of cohesin within gene bodies that are not engaged in loop formation, which is associated with reduced transcription. Importantly, degradation of cohesin in FACT-depleted cells restores transcriptional output, indicating that cohesin mislocalisation underlies this effect. Together, these findings demonstrate that FACT facilitates cohesin translocation along chromatin, promoting efficient loop extrusion while preventing its aberrant accumulation within transcribed regions. This work provides mechanistic insight into how chromatin structure modulates cohesin function to coordinate genome organisation with transcription in mammalian cells.

biochemistry↗

bioRxiv2021

Transactive response DNA-binding Protein (TDP-43) regulates early HIV-1 entry and infection.

The transactive response DNA-binding protein (TDP-43) is an important regulator of mRNA, being reported to stabilize the anti-HIV factor, histone deacetylase 6 (HDAC6). However, little is known about the role of TDP-43 in HIV infection. In this work, we seek for the TDP-43 function on regulating CD4+ T cell permissibility to HIV infection. We observed that over-expression of wt-TDP-43 in CD4+ T cells stabilized HDAC6, increasing mRNA and the protein levels of this antiviral enzyme. Under this experimental condition, HIV-1 infection was impaired, independently of the viral envelope glycoprotein (Env) complex tropism. The results obtained by using an HIV-1 Env-mediated cell-to-cell fusion model, under the same experimental conditions, suggest that the increase in TDP-43 levels negatively affects the viral Env fusion capacity. Moreover, the specific siRNA silencing of endogenous TDP-43 in target cells lead to a significant decrease in the levels of HDAC6 which consistently induces an increase in the fusogenic and infection activities of the HIV-1 Env. These observations were confirmed by using primary viral Envs from HIV+ individuals with different clinical phenotypes. An increase in the level of expression of wt-TDP-43 strongly reduced the Envs infection activity of viremic non-progressors (VNP) and rapid progressors (RP) HIV+ individuals down to the levels of the inefficient HIV-1 Envs from long-term non-progressor elite controllers (LTNP-EC) individuals. On the contrary, low levels of endogenous TDP-43, obtained after specific siRNA-TDP-43 knocking-down, significantly favors the infection activity of primary HIV-1 Envs of VNP and RP individuals, leading to an increase in the infection ability of the primary HIV-1/LTNP-EC Envs. Based on this evidence, we interpret that TDP-43 conditions cell permissibility to HIV infection by affecting viral Env fusion and infection capacities, at least by altering the cellular levels of the antiviral enzyme HDAC6.

immunology↗

bioRxiv2021

Cohesin is essential for the timely activation of condensin and anaphase segregation

Chromosome segregation requires both the separation of sister chromatids and the sustained condensation of chromatids during anaphase. In yeast cells, cohesin is not only required for sister chromatid cohesion but also plays a major role in determining the structure of individual chromatids in metaphase. Separase cleavage is thought to remove all cohesin complexes from chromosomes to initiate anaphase. It is thus not clear how the length and organisation of segregating chromatids are maintained during anaphase in the absence of cohesin. Here we show that degradation of cohesin at the anaphase onset causes aberrant chromatid segregation. Hi-C analysis on segregating chromatids demonstrates that cohesin depletion causes loss of intrachromatid organisation. Surprisingly, TEV-mediated cleavage of cohesin does not dramatically disrupt chromatid organisation in anaphase, explaining why bulk segregation is achieved. In addition, we identified a small pool of cohesin complexes bound to telophase chromosomes in wildtype cells and show that they play a role in the organisation of centromeric regions. Our data demonstrate that in yeast cells, cohesin function is not over in metaphase, but extends to the anaphase period when chromatids are segregating. One sentence summaryCohesin complexes on yeast chromosomes provide organisation to segregating chromatids.

cell biology↗

bioRxiv2019

FACT mediates cohesin function on chromatin

Cohesin is a key regulator of genome architecture with roles in sister chromatid cohesion 1,2 and the organisation of higher-order structures during interphase 3 and mitosis 4,5. The recruitment and mobility of cohesin complexes on DNA is restricted by nucleosomes 6-8. Here we show that cohesin role in chromosome organisation requires the histone chaperone FACT. Depletion of FACT in metaphase cells affects cohesin stability on chromatin reducing its accumulation at pericentric regions and binding on chromosome arms. Using Hi-C, we show that cohesin-dependent TAD (Topological Associated Domains)-like structures in G1 and metaphase chromosomes are disrupted in the absence of FACT. Surprisingly, sister chromatid cohesion is intact in FACT-depleted cells, although chromosome segregation failure is observed. Our results uncover a role for FACT in genome organisation by facilitating cohesin-dependent compartmentalization of chromosomes into loop domains.

molecular biology↗