2 Messenger RNA Transcription and Its Control in Saccharomyces cerevisiae

Abstract

I. INTRODUCTION
The regulation of transcription plays a critical role in the control of growth and differentiation in eukaryotic cells. The basis of this regulation in both eukaryotic cells and in prokaryotic cells is the activation or repression of a transcriptional apparatus (or machinery) by site-specific DNA-binding proteins. Fundamental differences exist between prokaryotes and eukaryotes in both the apparatus and site-specific regulators. The prokaryotic apparatus is the RNA polymerase core enzyme, which associates with any of several σ factors to acquire promoter specificity, whereas the eukaryotic apparatus consists of RNA polymerase, a protein that binds to the TATA box, and a series of other general transcription factors needed for specific initiation of transcription. Prokaryotic transcriptional activators and repressors, with few exceptions, bind in close proximity to the promoter site bound by RNA polymerase. In contrast, eukaryotic activators bind to upstream activation sites (UASs) or enhancers that can lie hundreds or thousands of bases away from the TATA box (Guarente 1984Guarente 1987; McKnight and Tjian 1986; Struhl 1987). The ability of these regulators to operate over such distances requires non-DNA-binding proteins, termed adaptors, that bridge the activators at the UASs to the general factors at the TATA boxes. Eukaryotic promoters can therefore be complex, with many different regulators influencing transcription at a particular TATA box.

One of the major themes to emerge from studies of transcriptional regulation in Saccharomyces cerevisiae in recent years is the remarkable conservation in this process from yeast to mammals. This conservation includes the components of the...