Biology subjects

Sanchez-Pozo, A.

Publications and source records attributed to Sanchez-Pozo, A..

3 recordsLinked to original sources

bioRxiv2024

BMAL1 represses transposable elements independently of CLOCK in pluripotent cells

Circadian oscillations of gene transcripts rely on a negative feedback loop executed by the activating BMAL1-CLOCK heterodimer and its negative regulators PER and CRY. Although circadian rhythms and CLOCK protein are mostly absent during embryogenesis, the lack of BMAL1 during prenatal development causes an early aging phenotype during adulthood, suggesting that BMAL1 carries out an unknown non-circadian function during organism development that is fundamental for healthy adult life. Here, we show that BMAL1 interacts with TRIM28 and represses transcription of totipotency-associated MERVL retrotransposons in mouse pluripotent cells. Deletion of Bmal1 leads to genome-wide upregulation of MERVLs, changes in the three-dimensional organization of the genome, and acquisition of totipotency-associated features. Overall, we demonstrate that in pluripotent cells BMAL1 is redeployed as a transcriptional repressor of transposable elements (TEs) in a CLOCK-independent way. We propose that BMAL1-TRIM28 activity during prenatal life is essential for optimal health and life span in mammals.

molecular biology↗

bioRxiv2022

Polycomb repression during S/G2 phases restrain initiation of cell differentiation to the G1 phase of the cell cycle

The potential of pluripotent cells to respond to developmental cues and trigger cell differentiation is enhanced during the G1 phase of the cell cycle, but the molecular mechanisms involved are poorly understood. Variations in polycomb activity during interphase progression have been hypothesized to regulate the cell-cycle-phase-dependent transcriptional activation of differentiation genes during lineage transition in pluripotent cells. Here, we asked whether the Polycomb Repressive Complex 1 (PRC1) modulates the ability of mouse embryonic stem cells (ESCs) to differentially respond to developmental cues depending on the phase of the cell cycle in which they are found. We discovered that recruitment of PRC1 complexes and their associated molecular functions, ubiquitination of H2AK119 and three-dimensional chromatin interactions, are enhanced during S and G2 phases compared to the G1 phase. In agreement with the accumulation of PRC1 at target promoters upon G1 phase exit, cells in S and G2 phases show firmer transcriptional repression of developmental regulator genes that is drastically perturbed upon genetic ablation of the PRC1 catalytic subunit Ring1b. Importantly, depletion of Ring1b during retinoic acid stimulation interferes with the preference of mESCs to induce the transcriptional activation of differentiation genes in G1 phase. We propose that incremental enrolment of polycomb repressive activity during interphase progression reduces the tendency of cells to respond to developmental cues during S and G2 phases, facilitating activation of cell differentiation in the G1 phase of the pluripotent cell cycle.

molecular biology↗

bioRxiv2022

EZH2 endorses cell plasticity to carcinoma cells facilitating mesenchymal to epithelial transition and tumour colonization

Reversible transition between the epithelial and mesenchymal states are key aspects of carcinoma cell dissemination and the metastatic disease, and thus, characterizing the molecular basis of the epithelial to mesenchymal transition (EMT) is crucial to find druggable targets and more effective therapeutic approaches in cancer. Emerging studies suggest that epigenetic regulators might endorse cancer cells with the cell plasticity required to conduct dynamic changes in cell state during EMT. However, epigenetic mechanisms involved remain mostly unknown. Polycomb Repressive Complexes (PRCs) proteins are well-established epigenetic regulators of development and stem cell differentiation, but their role in different cancer systems is inconsistent and sometimes paradoxical. In this study, we have analysed the role of the PRC2 protein EZH2 in lung carcinoma cells. We found that besides its described role in CDKN2A-dependent cell proliferation, EZH2 upholds the epithelial state of cancer cells by repressing the transcription of hundreds of mesenchymal genes. Chemical inhibition or genetic removal of EZH2 promotes the residence of cancer cells in the mesenchymal state during reversible epithelial-mesenchymal transition. In fitting, analysis of human patient samples and tumour xenograft models indicate that EZH2 is required to efficiently repress mesenchymal genes and facilitate tumour colonization in vivo. Overall, this study discloses a novel role of PRC2 as a master regulator of EMT in carcinoma cells. This finding has important implications for the design of therapies based on EZH2 inhibitors in human cancer patients.

cancer biology↗