RNA-POLYMERASE-II TRANSCRIPTION INITIATION - A STRUCTURAL VIEW

In eukaryotes, RNA polymerase II transcribes messenger RNAs and severa l small nuclear RNAs. Like RNA polymerases I and III, polymerase II ca nnot act alone. Instead, general initiation factors [transcription fac tor (TF) IIB, TFIID, TFIIE, TFIIF, and TFIIH] assemble on promoter DNA with polymerase II, creating a large multiprotein-DNA complex that su pports accurate initiation, Another group of accessory factors, transc riptional activators and coactivators, regulate the rate of RNA synthe sis from each gene in response to various developmental and environmen tal signals. Our current knowledge of this complex macromolecular mach inery is reviewed in detail, with particular emphasis on insights gain ed from structural studies of transcription factors.