Saccharomyces cerevisiae MSA1 mRNA has a sequence for localization at the bud tip

Abstract

MSA1 mRNA encodes Msa1p, a protein associated with the SCB-binding factor (SBF) and MCB-binding factor (MBF) complex. Msa1p promotes the transcription of G1 phase-specific genes, and is subjected to cell cycle-dependent regulation for its abundance and subcellular localization. MSA1 mRNA and Msa1p levels oscillate in the cell cycle with peaks at the late M/early G1 phase and early G1 phase, respectively. Phosphorylation by CDK1 negatively regulates the nuclear localization of Msa1p. In the present study, we identified MSA1 mRNA as a bud tip-localized mRNA in screening using a Tag-GFP system. A fragmentation analysis revealed a sequence of ~145 bases for the bud tip localization. Endogenous MSA1 mRNA localized at the bud tip in a manner that depended on SHE2. Msa1p levels were also affected by SHE2 in cells constitutively expressing MSA1 mRNA. These results suggest the existence of a regulatory mechanism for Msa1p through the localized control of MSA1 mRNA.