title: Identification of novel alternative splicing variants of interferon regulatory factor 3.
abstract: Interferon regulatory factor 3 (IRF-3) plays a crucial role in host defense against viral and microbial infection as well as in cell growth regulation. IRF-3a is the only structurally and functionally characterized IRF-3 splicing variant and has been established to antagonize IRF-3 activity. Here, five novel splicing variants of IRF-3, referred to as IRF-3b, -3c, -3d, -3e, and -3f, were identified and shown to be generated by deletion of exons 2, 3, or 6 or some combination thereof. RT-PCR examination revealed that these novel splicing variants were more frequently expressed in human liver, esophagus, and cervical tumor tissues than in their normal counterparts. Additionally, electrophoretic mobility shift assay and subcellular localization showed only IRF-3 and IRF-3e were capable of binding the PRDI/III element of interferon-beta (IFNβ) promoter in vitro and underwent cytoplasm-to-nucleus translocation following Poly(I:C) stimulation. Coimmunoprecipitation assay revealed that only IRF-3c (3f) of novel splicing variants associated with IRF-3 in vivo. Further luciferase assay showed IRF-3c (3f) and IRF-3e failed to transactivate PRDI/III-containing promoter but appeared to inhibit transactivation potential of IRF-3 to varying degrees. Taken together, our findings suggest novel splicing variants may function as negative modulators of IRF-3 and may be correlated with pathogenesis of human tumors.
authors.affiliation: Key laboratory of Carcinogenesis and Translational Research, Department of Genesis, Peking University School of Oncology , Beijing Cancer Hospital & Institute, Beijing, PR China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Li
authors.forename: Xiuhua
authors.initials: X
authors.lastname: Hu
authors.forename: Yuqin
authors.initials: Y
authors.lastname: Song
authors.forename: Zheming
authors.initials: Z
authors.lastname: Lu
authors.forename: Tao
authors.initials: T
authors.lastname: Ning
authors.forename: Hong
authors.initials: H
authors.lastname: Cai
authors.forename: Yang
authors.initials: Y
authors.lastname: Ke
mesh_terms: D017398:Alternative Splicing / Q000187:drug effects / Q000235:genetics*; D000595:Amino Acid Sequence; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D003001:Cloning, Molecular; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D050838:Interferon Regulatory Factor-3 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D016899:Interferon-beta / Q000235:genetics; D008969:Molecular Sequence Data; D011070:Poly I-C / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015533:Transcriptional Activation / Q000187:drug effects / Q000235:genetics
chemical_list: C494232:IRF3 protein, human; D050838:Interferon Regulatory Factor-3; D016899:Interferon-beta; D011070:Poly I-C