A Sequence Element Downstream of the Yeast HTB1 Gene Contributes to mRNA 3′ Processing and Cell Cycle Regulation

Abstract

ABSTRACT Histone mRNAs accumulate in the S phase and are rapidly degraded as cells progress into the G 2 phase of the cell cycle. In Saccharomyces cerevisiae , fusion of the 3′ untranslated region and downstream sequences of the yeast histone gene HTB1 to a neomycin phosphotransferase open reading frame is sufficient to confer cell cycle regulation on the resulting chimera gene ( neo-HTB1 ). We have identified a sequence element, designated the distal downstream element (DDE), that influences both the 3′-end cleavage site selection and the cell cycle regulation of the neo-HTB1 mRNA. Mutations in the DDE, which is located approximately 110 nucleotides downstream of the HTB1 gene, lead to a delay in the accumulation of the neo-HTB1 mRNA in the S phase and a lack of mRNA turnover in the G 2 phase. The DDE is transcribed as part of the primary transcript and binds a protein factor(s). Maximum binding is observed in the S phase of the cell cycle, and mutations that affect the turnover of the HTB1 mRNA alter the binding activity. While located in the same general region, mutations that affect 3′-end cleavage site selection act independently from those that alter the cell cycle regulation.