Regulation of eukaryotic gene expression by transactivating proteins and cis acting DNA elements.

In this review we try to examine some of the recent developments in our understanding of the mechanisms that control gene expression in eukaryotes. We discuss the nature of the positive regulation exerted by adenovirus, herpes virus or papova immediate early proteins. These proteins which can activate homologous promoters can also stimulate transcription from cellular promoters present on transfected DNA. This property of the E1a gene product of Adenovirus e.g. may be related to its immortalizing function. Transcription of cellular genes can be stimulated by viral or cellular short DNA elements named enhancers. These elements acting in cis, can be placed 5' or 3' to the gene and function in both orientations. Some of them show a remarkable cell specificity in their action. Enhancers affect the chromatin structure by creating a local nuclease sensitive region that may serve as an entry site for RNA polymerase II or for factors involved in the process of transcription initiation.