Abstract 2221: A new promoter of Casp 8 in an esophageal squamous cell carcinoma susceptibility locus

Abstract

Abstract Our previous Genome wide associationstudy (GWAS) of esophagealsquamous cell carcinoma (ESCC) identified a susceptibility locus on chromosome 2q33.1 encompassing CASP8 gene. Caspase 8 is an essential initiator in cell apoptosis and is associated with many diseases. CASP8 has varieties of transcripts, which might exert distinct functions. However, the transcriptional determinants, which control CASP8 gene expression remain poorly defined. The present study focused on revealing the mechanism behind the GWAS signal and finding clues for the complex regulation of CASP8.We observed a secondary promoter in CASP8 using a series of luciferase reporter assays, which locates 25kb far away from the previously described CASP8 promoter. The ENCODE ChIP-seq data shows the promoter features at the epigenetic level, including high H3K27Ac, H3K4M3 and low CpG methylation around the novel promoter region. Though people have known lots of transcription factors, little research focuses on which factors exert the transcription function for a certain promoteron earth. To explore the transcription factors that contribute to the secondary promoter of CASP8, we developed an effective strategy based on DNA-protein affinity purification and mass spectrometry. PURα was identified from the eluted protein products that the secondary promoter fragment could bind specific. We validated the mass spectrometry result through western blot analysis and immunoprecipitation assay and confirmed that PURα was involved in the transcription machine and might exert the function by forming a complex together with E2F-1 and Pol II. Remarkably, we observed that if knocking down the expression of PURα, the transcription activity decreased significantly. Although the physiologicrole of the CASP8 secondary promoter and its correspondent transcripts remain unclear, the current data suggest that it could explain the complexity of CASP8's transcription in some degree and expand the GWAS results to the function level. We believe these two promoters have thecapacity to play a role in the very different functions of caspase 8 isoforms. Note: This abstract was not presented at the meeting. Citation Format: Zhengwei Lin, Xiaohang Zhao, Yang Xu, Zhimin Guo, Nan Zhao, Yulin Sun. A new promoter of Casp 8 in an esophageal squamous cell carcinoma susceptibility locus. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2221. doi:10.1158/1538-7445.AM2014-2221