MODULATION OF POLYMERASE-II COMPOSITION - A POSSIBLE MODE OF TRANSCRIPTIONAL REGULATION OF STRESS-RESPONSE IN EUKARYOTES

Regulation of stress response in prokaryotes is mainly achieved at the transcriptional initiation level. Prokaryotes use alternative holoenz ymes, consisting of the core polymerase associated with different sigm a factors, which confer on it altered specificity of transcriptional i nitiation. Stress response being probably one of the most inevitable f eatures of life, it would be interesting to find if eukaryotes also us e a similar strategy at this level of regulation. Since the yeast Sacc haromyces cerevisiae is a model system for studying many different phe nomena in eukaryotes we review the transcriptional regulation of stres s in this system. Based on published observations in the literature an d our own studies, we have analysed the regulation of stress response in the yeast S. cerevisiae. Two of the core subunits of the yeast RNA polymerase II, which show altered stoichiometry within the polymerase under different conditions appear to be involved specifically in regul ating the stress response. In a very broad sense then, the altered sub unit composition of the core polymerase or a different holoenzyme, app ears to correlate with gene expression specific to stress response in S. cerevisiae and probably reflects the scenario in other eukaryotes.