ESCHERICHIA-COLI RHO-FACTOR INDUCES RELEASE OF YEAST RNA-POLYMERASE-II BUT NOT POLYMERASE-I OR POLYMERASE-III

Purified RNA polymerase II (pol II) from the yeast Saccharomyces cerev isiae pauses without releasing at many locations during in vitro trans cription. Pausing can be induced by intrinsic DNA sequence as well as by specific DNA bound proteins such as the RNA pol I termination facto r, Reb1p, or lac repressor. Addition of rho termination factor from E. coil induces RNA pol II to release at all of these pause sites, Rho-i nduced release of pol II requires both a rho binding site in the trans cript upstream of the pause sites as well as hydrolysis of ATP, In con trast, rho factor has no effect on either pausing or release by RNA po l I or III. When combined with previous observations, these results su ggest that RNA pol II may terminate by a mechanism closely related to the rho-dependent mechanism of prokaryotes. In contrast, pol I and III appear to utilize a mechanism more related to the rho-independent ter minators of prokaryotes.