SNF5 reexpression in malignant rhabdoid tumors regulates transcription of target genes by recruitment of SWI/SNF complexes and RNAPII to the transcription start site of their promoters.
Malignant rhabdoid tumor (MRT), a highly aggressive cancer of young children, displays inactivation or loss of the hSNF5/INI1/SMARCB1 gene, a core subunit of the SWI/SNF chromatin-remodeling complex, in primary tumors and cell lines. We have previously reported that reexpression of hSNF5 in some MRT cell lines causes a G1 arrest via p21(CIP1/WAF1) (p21) mRNA induction in a p53-independent manner. However, the mechanism(s) by which hSNF5 reexpression activates gene transcription remains unclear. We initially searched for other hSNF5 target genes by asking whether hSNF5 loss altered regulation of other consensus p53 target genes. Our studies show that hSNF5 regulates only a subset of p53 target genes, including p21 and NOXA, in MRT cell lines. We also show that hSNF5 reexpression modulates SWI/SNF complex levels at the transcription start site (TSS) at both loci and leads to activation of transcription initiation through recruitment of RNA polymerase II (RNAPII) accompanied by H3K4 and H3K36 modifications. Furthermore, our results show lower NOXA expression in MRT cell lines compared with other human tumor cell lines, suggesting that hSNF5 loss may alter the expression of this important apoptotic gene. Thus, one mechanism for MRT development after hSNF5 loss may rely on reduced chromatin-remodeling activity of the SWI/SNF complex at the TSS of critical gene promoters. Furthermore, because we observe growth inhibition after NOXA expression in MRT cells, the NOXA pathway may provide a novel target with clinical relevancy for treatment of this aggressive disease.
Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA.
Yasumichi
Y
Kuwahara
Darmood
D
Wei
Joel
J
Durand
Bernard E
BE
Weissman
D001932:Brain Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D042002:Chromatin Assembly and Disassembly / Q000235:genetics*; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007680:Kidney Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D012319:RNA Polymerase II / Q000235:genetics* / Q000378:metabolism; D018335:Rhabdoid Tumor / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000071796:SMARCB1 Protein; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D024363:Transcription Initiation Site; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism
D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C498702:PMAIP1 protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; D000071796:SMARCB1 Protein; C513266:SMARCB1 protein, human; C495901:TP53 protein, human; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D012319:RNA Polymerase II