The role of Xist‐mediated Polycomb recruitment in the initiation of X‐chromosome inactivation. (27th August 2019)

• Record Type: Journal Article
• Authors: Bousard, Aurélie; Raposo, Ana Cláudia; Żylicz, Jan Jakub; Picard, Christel; Pires, Vanessa Borges; Qi, Yanyan; Gil, Cláudia; Syx, Laurène; Chang, Howard Y; Heard, Edith; da Rocha, Simão Teixeira
• Is Part Of: EMBO reports. Volume 20:Number 10(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-08-27
• Subjects: chromatin -- PRC1 -- PRC2 -- X‐chromosome inactivation -- Xist; Molecular biology -- Periodicals; Molecular Biology -- Periodicals; Molecular biology; Periodicals; 572.8
• DOI: 10.15252/embr.201948019
• Languages: English
• ISSNs: 1469-221X

Abstract

Abstract: Xist RNA has been established as the master regulator of X‐chromosome inactivation (XCI) in female eutherian mammals, but its mechanism of action remains unclear. By creating novel Xist‐ inducible mutants at the endogenous locus in male mouse embryonic stem (ES) cells, we dissect the role of the conserved A‐B‐C‐F repeats in the initiation of XCI. We find that transcriptional silencing can be largely uncoupled from Polycomb repressive complex 1 and complex 2 (PRC1/2) recruitment, which requires B and C repeats. Xist ΔB+C RNA specifically loses interaction with PCGF3/5 subunits of PRC1, while binding of other Xist partners is largely unaffected. However, a slight relaxation of transcriptional silencing in Xist ΔB+C indicates a role for PRC1/2 proteins in early stabilization of gene repression. Distinct modules within the Xist RNA are therefore involved in the convergence of independent chromatin modification and gene repression pathways. In this context, Polycomb recruitment seems to be of moderate relevance in the initiation of silencing. Synopsis: Distinct modules of the Xist RNA are involved in Polycomb recruitment and initiation of gene silencing. The coordinated convergence of these two pathways is ultimately important to ensure the repressed state of the inactive X‐chromosome. Xist ‐mediated PRC1 and PRC2 recruitment involves the conserved B and C repeats. Transcriptional silencing can be initiated without Xist ‐mediated Polycomb recruitment. Absence of Xist ‐mediated Polycomb recruitment results in moderate relaxation of transcriptional silencing, suggesting a role in early stabilization of gene repression. Abstract : Distinct modules of the Xist RNA are involved in Polycomb recruitment and initiation of gene silencing. The coordinated convergence of these two pathways is ultimately important to ensure the repressed state of the inactive X‐chromosome.