The mechanism of transcription termination by RNA poiymerase I

SummaryEukaryotic ribosomal gene transcription units are bordered at their 3’ends by short DNA sequences which specify site‐specific termination by RNA polymerase I (poll). Poll terminators from yeast through to mammals appear to follow similar rules: they contain a site for a sequence‐specific DNA‐binding protein; they function only in one orientation; 3’ends are formed upstream of the binding site; and 5’flanking sequences influence the position and efficiency of 3’end formation. Recent progress in understanding the mechanism of RNA chain elongation by other polymerases suggests a model for poll termination in which termination is seen as one of the several outcomes possible when a polymerase encounters a pause site.