title: Interferon-γ upregulates expression of IFP35 gene in HeLa cells via interferon regulatory factor-1.
abstract: BACKGROUND
  Interferon-induced 35-kDa protein (IFP35) plays important roles in antiviral defense and the progression of some skin cancer diseases. It can be induced by interferon-γ (IFN-γ) in multiple human cells. However, the mechanisms by which IFN-γ contributes to IFP35 induction remain to be elucidated.
  
  
  RESULTS
  We identified the transcription start sites of IFP35 by 5' rapid amplification of cDNA ends (RACE) and cloned the promoter of IFP35. Sequence analysis and luciferase assays revealed two GC boxes and an IFN-stimulated response element (ISRE) in the 5' upstream region of the transcription start sites, which were important for the basal transcription of IFP35 gene. Furthermore, we found that interferon regulatory factor 1 (IRF-1) and IRF-2 could bind to IFP35 promoter and upregulate endogenous IFP35 protein level. Depletion of endogenous IRF-1 by interfering RNA reduced the constitutive and IFN-γ-dependent expression of IFP35, whereas depletion of IRF-2 had little effect on IFN-γ-inducible IFP35 expression. Moreover, IRF-1 was recruited to the ISRE site in IFP35 promoter in IFN-γ treated HeLa cells, as demonstrated by electrophoretic mobility shift and chromatin immunoprecipitation assays.
  
  
  CONCLUSIONS
  These findings provide the first evidence that IRF-1 and IRF-2 are involved in constitutive IFP35 expression in HeLa cells, while IRF-1 also activates IFP35 expression in an IFN-γ-inducible manner. Our data therefore identified a new IRF-1 and IRF-2 target gene, which may expand our current understanding of the versatile functions of IRF-1 and IRF-2.
authors.affiliation: Key Laboratory of Molecular Microbiology and Biotechnology, Ministry of Education and Key Laboratory of Microbial Functional Genomics Tianjin, College of Life Sciences, Nankai University, Tianjin, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
authors.forename: Juan
authors.initials: J
authors.lastname: Tan
authors.forename: Ruikang
authors.initials: R
authors.lastname: Liu
authors.forename: Xiaoxu
authors.initials: X
authors.lastname: Cui
authors.forename: Qinglin
authors.initials: Q
authors.lastname: Ma
authors.forename: Yunqi
authors.initials: Y
authors.lastname: Geng
authors.forename: Wentao
authors.initials: W
authors.lastname: Qiao
mesh_terms: D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D016384:Consensus Sequence / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D050856:Interferon Regulatory Factor-1 / Q000378:metabolism*; D050835:Interferon Regulatory Factors / Q000378:metabolism; D007371:Interferon-gamma / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D020218:Response Elements / Q000235:genetics; D050794:STAT1 Transcription Factor / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics*
chemical_list: C085378:IFI35 protein, human; C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; D050835:Interferon Regulatory Factors; D047908:Intracellular Signaling Peptides and Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D007371:Interferon-gamma