title: Downregulation of splicing factor SRSF3 induces p53β, an alternatively spliced isoform of p53 that promotes cellular senescence.
abstract: Most human pre-mRNA transcripts are alternatively spliced, but the significance and fine-tuning of alternative splicing in different biological processes is only starting to be understood. SRSF3 (SRp20) is a member of a highly conserved family of splicing factors that have critical roles in key biological processes, including tumor progression. Here, we show that SRSF3 regulates cellular senescence, a p53-mediated process to suppress tumorigenesis, through TP53 alternative splicing. Downregulation of SRSF3 was observed in normal human fibroblasts undergoing replicative senescence, and was associated with the upregulation of p53β, an alternatively spliced isoform of p53 that promotes p53-mediated senescence. Knockdown of SRSF3 by short interfering RNA (siRNA) in early-passage fibroblasts induced senescence, which was associated with elevated expression of p53β at mRNA and protein levels. Knockdown of p53 partially rescued SRSF3-knockdown-induced senescence, suggesting that SRSF3 acts on p53-mediated cellular senescence. RNA pulldown assays demonstrated that SRSF3 binds to an alternatively spliced exon uniquely included in p53β mRNA through the consensus SRSF3-binding sequences. RNA crosslinking and immunoprecipitation assays (CLIP) also showed that SRSF3 in vivo binds to endogenous p53 pre-mRNA at the region containing the p53β-unique exon. Splicing assays using a transfected TP53 minigene in combination with siRNA knockdown of SRSF3 showed that SRSF3 functions to inhibit the inclusion of the p53β-unique exon in splicing of p53 pre-mRNA. These data suggest that downregulation of SRSF3 represents an endogenous mechanism for cellular senescence that directly regulates the TP53 alternative splicing to generate p53β. This study uncovers the role for general splicing machinery in tumorigenesis, and suggests that SRSF3 is a direct regulator of p53.
authors: Laboratory of Human Carcinogenesis, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4258, USA.
authors: Y
authors: Y
authors: Tang
authors: I
authors: I
authors: Horikawa
authors: M
authors: M
authors: Ajiro
authors: A I
authors: AI
authors: Robles
authors: K
authors: K
authors: Fujita
authors: A M
authors: AM
authors: Mondal
authors: J K
authors: JK
authors: Stauffer
authors: Z-M
authors: ZM
authors: Zheng
authors: C C
authors: CC
authors: Harris
mesh_terms: D017398:Alternative Splicing / Q000235:genetics*; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D016922:Cellular Senescence / Q000235:genetics; D015536:Down-Regulation; D005347:Fibroblasts; D006801:Humans; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D012322:RNA Precursors / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000068103:Serine-Arginine Splicing Factors; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D020033:Protein Isoforms; D012322:RNA Precursors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; C491388:SRSF3 protein, human; D016159:Tumor Suppressor Protein p53; D000068103:Serine-Arginine Splicing Factors