NF-1 and octamer binding proteins in Mouse Mammary Tumor Virus transcription

Abstract

The Mouse Mammary Tumor Virus (MMTV) is currently one of the best understood steroid hormone inducible systems. The hormone response element (HRE), which functions as a hormone-inducible enhancer has been well characterized, and the genes encoding several steroid hormone receptors have been cloned. In contrast, relatively less is known about the functional elements of the basal level promoter and the transcription factors which bind to the promoter. Both aspects, hormone-induced transcription and basal level transcription, are important in understanding transcription. The purpose of the work presented in this dissertation is to provide evidence for MMTV promoter transcription factors. The focus is then directed toward providing in vitro and in vivo evidence for the importance of two transcription factors, Nuclear Factor 1 (NF-1) and an octamer-related binding protein(s). In addition to the ubiquitous Oct-1 protein, a 40kD protein was found to bind to the MMTV octamer region. It is still not known which protein mediates MMTV transcription in vivo. Protein/protein interactions are postulated to take place based on evidence from other transcriptional systems and the organization of the putative binding sites for MMTV transcription factors. Evidence is presented for protein/protein interactions between some MMTV transcription factors. Overall, these results suggests a complex interaction of several proteins with DNA and with each other in the regulation of MMTV transcription.