In Vivo and In Vitro Analysis of the Regulation of c-myc Proto-OncogeneExpression in Human Breast Cancer

摘要

The purpose of this research is to characterize the factors controlling theexpression of c-myc and other genes that are commonly mis-regulated in transformed cells, Genomic DNA exists in the form of chromatin, which generally renders the DNA inaccessible to factors that promote gene expression. Here we report characterization of a cellular protein complex, hSW1/SNF, that can alter chromatin structure and facilitate the interaction of transcription factors with chromatin. The results indicate that the change in chromatin structure induced by hSW1/SNF is stable and not transient in nature, that hSW1/SNF activity requires ATP hydrolysis, that the hydrolysis of ATP is likely utilized to alter the chromatin structure as opposed to modifying or altering the conformation of hSW1/SNF, and that the increased ability of transcription factors to bind to chromatin is not dependent on concurrent hSW1/SNF activity, which indicates that hS1/SNF facilitated binding of transcription factors to nucleosomal DNA is a multi-step process. The results also show that hSWI/SNF can increase transcriptional elongation in vitro on a reconstituted nucleosomal human hsp7O promoter, a promoter that, like c-myc, is regulated at the level of transcription initiation and transcription elongation.