title: Identification of a secondary promoter of CASP8 and its related transcription factor PURα.
abstract: Caspase-8 (CASP8) is an essential initiator of apoptosis and is associated with many diseases in humans including esophageal squamous cell carcinoma. CASP8 produces a variety of transcripts, which might perform distinct functions. However, the cis and trans transcriptional determinants that control CASP8 expression remain poorly defined. Using a series of luciferase reporter assays, we identified a novel secondary promoter of CASP8 within chr2: 202,122,236 to 202,123,227 and 25 kb downstream of the previously described CASP8 promoter. ENCODE ChIP-seq data for this novel promoter region revealed several epigenetic features, including high levels of histone H3 lysine 27 acetylation and lysine 4 methylation, as well as low levels of CpG island methylation. We developed a mass spectrometry based strategy to identify transcription factors that contribute to the function of the secondary promoter. We found that the transcription activator protein PURα is specifically involved in the transcriptional activation of the secondary promoter and may exert its function by forming a complex with E2F-1 and RNA polymerase II. PURα can bind to both DNA and RNA, and functions in the initiation of DNA replication, regulation of transcription. We observed that knockdown of PURα expression decreased the transcriptional activity of the secondary promoter and mRNA expression of CASP8 isoform G. Although the physiologic roles of this secondary promoter remain unclear, our data may help explain the complexity of CASP8 transcription and suggest that the various caspase 8 isoforms may have distinct regulations and functions.
authors.affiliation: State Key Laboratory of Molecular Oncology, Cancer Institute and Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, P.R. China.
authors.forename: Zhengwei
authors.initials: Z
authors.lastname: Lin
authors.affiliation: State Key Laboratory of Molecular Oncology, Cancer Institute and Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, P.R. China.
authors.forename: Zhimin
authors.initials: Z
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Molecular Oncology, Cancer Institute and Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, P.R. China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Molecular Oncology, Cancer Institute and Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, P.R. China.
authors.forename: Xiaohang
authors.initials: X
authors.lastname: Zhao
mesh_terms: D020121:5' Untranslated Regions; D001483:Base Sequence; D053181:Caspase 8 / Q000235:genetics*; D045744:Cell Line, Tumor; D002889:Chromosomes, Human, Pair 2; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D050687:E2F1 Transcription Factor / Q000378:metabolism*; D044127:Epigenesis, Genetic; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012319:RNA Polymerase II / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*
chemical_list: D020121:5' Untranslated Regions; D004268:DNA-Binding Proteins; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; C501130:PURA protein, human; D020033:Protein Isoforms; D014157:Transcription Factors; D012319:RNA Polymerase II; C505530:CASP8 protein, human; D053181:Caspase 8