Preliminary Functional Analysis Of Human CREB4 Gene

Signal-transduction pathways converge ultimately at the level of transcriptional activation to produce specific patterns of gene expression in response to environmental stimuli. The initiation of transcription mediated by these signaling pathways is regulated by the coordinate expression and/or activation of specific transcription factors that bind to the control regions of genes. Specific insights into the mechanisms underlying transcriptional activation have recently arisen from studies of the structure and functions of these transcription factors. The mammalian CREB/ATF family represents a large group of basic-region leucine zipper(bzip) transcription factors with rather diverse physiological functions.CREB4 is a novel member of human CREB/ATF family. RT-PCR showed CREB4 was broadly expressed in various human tumor tissues such as lung carcinoma LX-1, colon adenocarcinoma CX-1, prastatic adenocarcinoma PC-3, colon carcinoma Gl-112, and pancreatic adenocarcinoma Gl-103, whereas specific bands of the transcript could not be detected in breast carcinoma GI-101, ovarian carcinoma GI-102 and lung carcinoma GI-117. In addition, our results of human tumor MTC panel showed obvious transcripts in lung carcinoma LX-1, colon adenocarcinoma CX-1 and colon carcinoma Gl-112, whereas in normal lung and colon tissues transcripts could not be detected, which suggested that CREB4 may be involved in the development of lung carcinoma, colon adenocarcinoma and colon carcinoma.Subcellular location of CREB4 and CREB4^1-279aa showed that a fusion protein of GFP and full-length CREB4 was localized in cytoplasm, whereas the fusion protein of GFP and a deletion mutant lacking the C-terminal putative transmembrane domain was translocated in nucleus, which suggested that the process of translocation of CREB4 from cytoplasm to nucleus is associated with the lack of C-terminal of CREB4 protein.Constructing CREB4 and CREB^215-395aafusion protein with the entire prokaryotic LexA protein respectively to done yeast-two-hybrid analysis disclosed that CREB4 protein functioned as a transcription activator and its N-terminal accounted for the activation ability.Yeast two-hybrid system revealed 2 proteins, TPR and KPNA2 ,may associate with CREB4^215-279. TPR was a nuclear pore complex associated protein. KPNA2 was concerned with the Karyopherin a 2 β 1 pathways mediated by receptor to assist the translocation of proteins from cytoplasm to nucleous. These results suggested that TPR and KPN A2 may be associated with translocation of CREB4.