Chorionic gonadotropin (CG) is a heterodimeric hormone that is encoded by separate alpha and beta subunit genes. The biological function of CG, as a placental hormone, is to stimulate steroidogenesis in the corpus luteum, providing an essential step in the maintenance of early pregnancy. CG is produced ectopically. by many different neoplasms and CGalpha and beta sub unit genes are expressed in the placenta at a time of rapid cellular proliferation. The focus of this proposal is on the transcriptional control of the CGalpha and beta subunit genes, in particular to determine those factors involved in ectopic expression of the CG genes in tumors. An integrated series of studies are proposed to identify regulatory DNA elements within a limited region of the CGalpha and beta promoters and to use these sequences as tools to identify transcription factors that regulate CG gene expression during dedifferentiation and tumorigenesis. Several different cellular proto- oncogenes and transforming viruses have been shown to act as regulators of gene transcription. This current proposal will focus on transcriptional regulation of the CG genes by the cellular proto- oncogenes c-jun and c-fos and the transforming virus E1A, (referred to together here as Transforming Factors- TFs), in tumor cell lines. Portions of the CGalpha and beta promoters will be linked to the luciferase reporter gene and transfected into cell lines in conjunction with vectors driving expression of the TF. In this manner regions of the CG promoter regulated by these TFs will be identified. Structural domains of the TFs involved in regulating CG transcription will be determined through overexpressing wild type and mutant TF proteins with the CG reporter gene containing the known responsive DNA element(s). Previous studies defining domains of E1A involved in transformation enable us to use this viral protein as a """"""""molecular probe"""""""" of the mechanisms responsible for E1A induced transcription of human genes in cultured human cells. The region(s) of the CG promoter interacting with these TFs will be used as probes to identify other genes coding for protein(s) that bind these DNA regions through expression cloning techniques. These cloned genes will be sequenced to determine whether they resemble known transforming factors, and the abundance of the protein from these cloned genes determined in ectopic tumors and transformed cells. These cloned genes will be expressed and their effects on the CGalpha and CGbeta promoters determined in ectopic cell lines. Mutational studies of the cloned proteins will determine their mechanism of CG promoter transregulation. Identification of target proteins that modulate TF mediated transcription of human genes, may identify key factors governing the process of tumorigenesis.
| Xiong, W; Pestell, R G; Watanabe, G et al. (1997) Cyclin D1 is required for S phase traversal in bovine tracheal myocytes. Am J Physiol 272:L1205-10 |
