Transcription elongation: Structural basis and mechanisms

A ternary complex composed of RNA polymerase (RNAP), DNA template, and RNA transcript is the central intermediate in the transcription cycle responsib le for the elongation of the RNA chain. Although the basic biochemistry of RNAP functioning is well understood, little is known about the underlying s tructural determinants. The absence of high-resolution structural data has hampered our understanding of RNAP mechanism. However, recent work suggests a structure-function model of the ternary elongation complex, if not at a defined structural level, then at least as a conceptual view, such that key components of RNAP are defined operationally on the basis of compelling bi ochemical, protein chemical, and genetic data. The model has important impl ications for mechanisms of transcription elongation and also for initiation and termination. (C) 1999 Academic Press.