Promoter specificity and modulation of RNA polymerase II transcription.

RNA polymerase II is a multisubunit enzyme involved in the transcription of protein encoding genes. Recently acquired knowledge of the transcription process and of the RNA polymerase molecule as well as the isolation of subunit clones have led to a better understanding of the enzyme's functional regulation. Specific transcription initiation occurs at promoter regions located upstream of the gene and requires a minimum of five basic factors in addition to the enzyme. Furthermore, proteins that bind to specific DNA elements within the promoter also regulate transcriptional activity. Additional factors are required for the elongation and, possibly, termination of transcription. Two elongation factors, SII and TFIIF, interact directly with the RNA polymerase II molecule. Functional domains of RNA polymerase II have been determined by analysis of genomic clones for the two largest subunits of the enzyme. For example, the 240-kDa largest subunit contains a highly phosphorylated carboxyl-terminal heptapeptide domain repeated 26-52 times that is absolutely required for transcription in vivo. Analysis of the polymerase molecule and its interaction with basic gene-specific transcription factors will aid in our studies of the control of gene expression.