title: Alternative splicing of FBP-interacting repressor coordinates c-Myc, P27Kip1/cyclinE and Ku86/XRCC5 expression as a molecular sensor for bleomycin-induced DNA damage pathway.
abstract: The far-upstream element-binding protein-interacting repressor (FIR) is a c-myc transcriptional suppressor. FIR is alternatively spliced to lack the transcriptional repression domain within exon 2 (FIRΔexon2) in colorectal cancers. FIR and FIRΔexon2 form homo- or heterodimers that complex with SAP155. SAP155, a subunit of the essential splicing factor 3b subcomplex in the spliceosome, is required for proper P27Kip1 pre-mRNA splicing, and P27Kip1 arrests cells at G1. In contrast, FIR was co-immunoprecipitated with Ku86 and DNA-PKcs. siRNA against Ku86/Ku70 decreased FIR and P27Kip1 expression, whereas siRNA against FIR decreased Ku86/XRCC5 and P27Kip1 expression. Thus the mechanical interaction of FIR/FIRΔexon2/SAP155 bridges c-myc and P27Kip1 expression, potentially integrates cell-cycle progression and c-myc transcription in cell. Bleomycin(BLM) is an anticancer agent that introduces DNA breaks. Because DNA breaks generate the recruitment of Ku86/Ku70 to bind to the broken DNA ends, the possible involvement of FIR and Ku86/Ku70 interaction in the BLM-induced DNA damage repair response was investigated in this study. First, BLM treatment reduced SAP155 expression and increased FIR and FIRΔexon2 mRNA expression as well as the ratio of FIRΔexon2:FIR in hepatoblastoma cells (HLE and HLF). Second, FIR or FIRΔexon2 adenovirus vectors (Ad-FIR or Ad-FIRΔexon2) increased Ku86/Ku70 and P27Kip1 expression in vitro. Third, BLM decreased P27Kip1 protein expression, whereas increased P27Kip1 and γH2AX expression with Ad-FIRΔexon2. Together, the interaction of FIR/SAP155 modulates FIR splicing and involves in cell-cycle control or cell fate via P27Kip1 and c-myc in BLM-induced DNA damage pathway. This novel function of FIR splicing will contribute to clinical studies of cancer management through elucidating the mechanical interaction of FIR/FIRΔexon2/SAP155 as a potential target for cancer treatment.
authors.affiliation: Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Chiba City, Chiba, Japan.
authors.forename: Bahityar
authors.initials: B
authors.lastname: Rahmutulla
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Matsushita
authors.forename: Mamoru
authors.initials: M
authors.lastname: Satoh
authors.forename: Masanori
authors.initials: M
authors.lastname: Seimiya
authors.forename: Sachio
authors.initials: S
authors.lastname: Tsuchida
authors.forename: Shuji
authors.initials: S
authors.lastname: Kubo
authors.forename: Hideaki
authors.initials: H
authors.lastname: Shimada
authors.forename: Masayuki
authors.initials: M
authors.lastname: Ohtsuka
authors.forename: Masaru
authors.initials: M
authors.lastname: Miyazaki
authors.forename: Fumio
authors.initials: F
authors.lastname: Nomura
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D001761:Bleomycin / Q000494:pharmacology*; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage / Q000187:drug effects*; D004265:DNA Helicases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000187:drug effects / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005434:Flow Cytometry; D018197:Hepatoblastoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D000072200:Ku Autoantigen; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism*; D000072260:RNA Splicing Factors; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D016601:RNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D012097:Repressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D000903:Antibiotics, Antineoplastic; D016271:Proto-Oncogene Proteins c-myc; D000072260:RNA Splicing Factors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; C410595:poly-U binding splicing factor 60KDa; D001761:Bleomycin; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004265:DNA Helicases; C106893:XRCC5 protein, human; D000072200:Ku Autoantigen