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      BRG1 Activates Proliferation and Transcription of Cell Cycle-Dependent Genes in Breast Cancer Cells

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          Abstract

          Cancer malignancy is usually characterized by unlimited self-renewal. In some types of advanced tumors that are rapidly dividing, gene expression profiles depict elevations in pro-proliferative genes accompanied by coordinately elevated transcription of factors responsible for removal of DNA lesions. In our studies, fast proliferating breast cancer cell lines (MDA-MB-231 and MCF7), BRG1, a component of the SWI/SNF complex, emerges as an activator of functionally-linked genes responsible for activities such as mitotic cell divisions and DNA repair. Products of at least some of them are considerably overrepresented in breast cancer cells and BRG1 facilitates growth of MCF7 and MDA-MB-231 cell lines. BRG1 occurs at the promoters of genes such as CDK4, LIG1, and NEIL3, which are transcriptionally controlled by cell cycle progression and highly acetylated by EP300 in proliferating cells. As previously documented, in dividing cells BRG1 directly activates gene transcription by evicting EP300 modified nucleosomes from the promoters and, thereby, relaxing chromatin. However, the deficiency of BRG1 or EP300 activity for 48 h leads to cell growth arrest and to chromatin compaction, but also to the assembly of RB1/HDAC1/EZH2 complexes at the studied cell cycle-dependent gene promoters. Epigenetic changes include histone deacetylation and accumulation of H3K27me trimethylation, both known to repress transcription. Cell cycle arrest in G1 by inhibition of CDK4/6 phenocopies the effect of the long-term BRG1 inhibition on the chromatin structure. These results suggest that BRG1 may control gene transcription also by promoting expression of genes responsible for cell cycle progression in the studied breast cancer cells. In the current study, we show that BRG1 binding occurs at the promoters of functionally linked genes in proliferating breast cancer cells, revealing a new mechanism by which BRG1 defines gene transcription.

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          Manipulation of FASTQ data with Galaxy

          Summary: Here, we describe a tool suite that functions on all of the commonly known FASTQ format variants and provides a pipeline for manipulating next generation sequencing data taken from a sequencing machine all the way through the quality filtering steps. Availability and Implementation: This open-source toolset was implemented in Python and has been integrated into the online data analysis platform Galaxy (public web access: http://usegalaxy.org; download: http://getgalaxy.org). Two short movies that highlight the functionality of tools described in this manuscript as well as results from testing components of this tool suite against a set of previously published files are available at http://usegalaxy.org/u/dan/p/fastq Contact: james.taylor@emory.edu; anton@bx.psu.edu Supplementary information: Supplementary data are available at Bioinformatics online.
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            The retinoblastoma protein and BRG1 form a complex and cooperate to induce cell cycle arrest.

            The retinoblastoma tumor suppressor protein (RB) binds several cellular proteins involved in cell cycle progression. Using the yeast two-hybrid system, we found that RB bound specifically to the protein BRG1. BRG1 shares extensive sequence similarity to Drosophila brahma, an activator of homeotic gene expression, and the yeast transcriptional activator SNF2/SW12. BRG1 contains an RB-binding motif found in viral oncoproteins and bound to the A/B pocket and the hypophosphorylated form of RB. BRG1 did not bind RB in viral oncoprotein-transformed cells. Coimmunoprecipitation experiments suggested BRG1 associates with the RB family in vivo. In the human carcinoma cell line SW13, BRG1 exhibited tumor suppressor activity by inducing formation of flat, growth-arrested cells. This activity depended on the ability of BRG1 to cooperate and complex with RB, as both an RB-nonbinding mutant of BRG1 and the sequestration of RB by adenovirus E1A protein abolished flat cell formation.
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              Rad51 paralog complexes BCDX2 and CX3 act at different stages in the BRCA1-BRCA2-dependent homologous recombination pathway.

              The Rad51 paralogs are required for homologous recombination (HR) and the maintenance of genomic stability. The molecular mechanisms by which the five vertebrate Rad51 paralogs regulate HR and genomic integrity remain unclear. The Rad51 paralogs associate with one another in two distinct complexes: Rad51B-Rad51C-Rad51D-XRCC2 (BCDX2) and Rad51C-XRCC3 (CX3). We find that the BCDX2 and CX3 complexes act at different stages of the HR pathway. In response to DNA damage, the BCDX2 complex acts downstream of BRCA2 recruitment but upstream of Rad51 recruitment. In contrast, the CX3 complex acts downstream of Rad51 recruitment but still has a marked impact on the measured frequency of homologous recombination. Both complexes are epistatic with BRCA2 and synthetically lethal with Rad52. We conclude that human Rad51 paralogs facilitate BRCA2-Rad51-dependent homologous recombination at different stages in the pathway and function independently of Rad52.
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                Author and article information

                Journal
                Cancers (Basel)
                Cancers (Basel)
                cancers
                Cancers
                MDPI
                2072-6694
                04 February 2020
                February 2020
                : 12
                : 2
                : 349
                Affiliations
                [1 ]Department of General Biophysics, Institute of Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz, Poland; maciej.sobczak@ 123456unilodz.eu (M.S.); julita.pietrzak@ 123456unilodz.eu (J.P.)
                [2 ]Department of Clinical and Laboratory Genetics, Medical University of Lodz, Pomorska 251, 92-213 Lodz, Poland; tomasz.ploszaj@ 123456umed.lodz.pl
                Author notes
                [* ]Correspondence: agnieszka.robaszkiewicz@ 123456biol.uni.lodz.pl ; Tel./Fax: +48-42-6354449
                Author information
                https://orcid.org/0000-0002-6265-5585
                Article
                cancers-12-00349
                10.3390/cancers12020349
                7072512
                32033115
                01582eef-f9b0-4bdc-8fcb-79c59dd95bf6
                © 2020 by the authors.

                Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/).

                History
                : 24 December 2019
                : 23 January 2020
                Categories
                Article

                brg1 (brahma-related gene 1),ep300 (e1a binding protein p300),gene transcription,breast cancer epigenetics

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