De-regulated expression of the BRG1 chromatin remodeling factor in bone marrow mesenchymal stromal cells induces senescence associated with the silencing of NANOG and changes in the levels of chromatin proteins.
Stem cells have a peculiar chromatin architecture that contributes to their unique properties, including uncommitted status, multi/pluripotency and self-renewal. We analyzed the effect of the de-regulation of the SWI/SNF chromatin remodeling complex in mesenchymal stromal cells (MSC) through the silencing and up-regulation of BRG1, which is the ATPase subunit of the complex. The altered expression of BRG1 promoted the senescence of MSC with suppression of the NANOG transcription, which is part of the transcriptional circuitry governing stem cell functions. To gain insight on the way NANOG was silenced, we evaluated how the de-regulated BRG1 expression affect the binding of activators and repressors on the NANOG promoter. We found 4 E2F binding motifs on NANOG promoter, which can be occupied by RB1 and RB2/P130. These are members of the retinoblastoma gene family. In MSC with a silenced BRG1, the relative binding of the 2 retinoblastoma proteins increased, and this was associated with the recruitment of DNMT1. This induced the methylation of CpG on the NANOG promoter. Opposingly, when a high level of BRG1 was present, the same E2F binding motifs were docking sites for BRG1, which induced chromatin compaction without CpG methylation but with increased histone deacetylation, associated with the presence of HDAC1 on E2F binding sites. Besides the sharp regulation of the NANOG expression, we evidenced, through proteomic analysis, that the de-regulation of the SWI/SNF function affected the expression of histones and other nuclear proteins involved in "nuclear architecture," suggesting that BRG1 may act as global regulator of gene expression.
a Department of Experimental Medicine; Biotechnology and Molecular Biology Section ; Second University of Naples ; Naples , Italy.
Tiziana
T
Squillaro
Valeria
V
Severino
Nicola
N
Alessio
Annarita
A
Farina
Giovanni
G
Di Bernardo
Marilena
M
Cipollaro
Gianfranco
G
Peluso
Angela
A
Chambery
Umberto
U
Galderisi
D001665:Binding Sites; D001854:Bone Marrow Cells / Q000166:cytology; D002478:Cells, Cultured; D016922:Cellular Senescence; D002843:Chromatin / Q000378:metabolism*; D042002:Chromatin Assembly and Disassembly; D050719:Crk-Associated Substrate Protein / Q000378:metabolism; D004265:DNA Helicases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D019175:DNA Methylation; D050684:E2F Transcription Factors / Q000378:metabolism; D005786:Gene Expression Regulation; D056284:Histone Deacetylase 1 / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D018398:Homeodomain Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism*; D000071317:Nanog Homeobox Protein; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry / Q000378:metabolism; D015854:Up-Regulation
C493841:BCAR1 protein, human; D002843:Chromatin; D050719:Crk-Associated Substrate Protein; D050684:E2F Transcription Factors; D006657:Histones; D018398:Homeodomain Proteins; C486780:NANOG protein, human; D000071317:Nanog Homeobox Protein; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D016160:Retinoblastoma Protein; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; C110550:HDAC1 protein, human; D056284:Histone Deacetylase 1; C084108:SMARCA4 protein, human; D004265:DNA Helicases
mesenchymal stem cells; proteome; retinoblastoma; senescence