J. Biol. Chem., Vol. 264, Issue 33, 19528-19534, 11, 1989
rRNA transcription initiation is decreased by inhibitors of the yeast cell cycle control step "start"
LM Veinot-Drebot, RA Singer and GC Johnston
Department of Microbiology, Dalhousie University, Halifax, Nova Scotia, Canada.
Inhibitors of the "start" regulatory step in the cell cycle of the yeast
Saccharomyces cerevisiae are known by indirect studies to perturb RNA
metabolism. We have investigated these effects further and show here by a
pulse-labeling and quantitative hybridization procedure that pre-rRNA
transcription was substantially decreased by five inhibitors of start but
was transiently stimulated by the mating pheromone alpha- factor. Thus in
contrast to the effects of the other start inhibitors, the inhibition of
start by alpha-factor is unrelated to this aspect of biosynthetic activity.
Mating factor treatment also stimulated the synthesis rate of poly(A)+ RNA.
The start inhibitors o-phenanthroline and L-ethionine inhibited pre-rRNA
transcription with little effect on poly(A)+ RNA synthesis rates. Northern
analysis showed that all inhibitors of start also inhibited pre-rRNA
transcript cleavage, a process that has been dissociated from the
inhibition of start. Most inhibitors also affected ATP pool size. One
inhibitor, o- phenanthroline, markedly induced the general control
response.