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MSA1mRNA 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.MSA1mRNA 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 identifiedMSA1mRNA 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. EndogenousMSA1mRNA localized at the bud tip in a manner that depended onSHE2. Msa1p levels were also affected bySHE2in cells constitutively expressingMSA1mRNA. These results suggest the existence of a regulatory mechanism for Msa1p through the localized control ofMSA1mRNA. [ABSTRACT FROM PUBLISHER]

RNA localization is an important event that is essential for the polarization and differentiation of a cell. Although several methods are currently used to detect localized RNAs, a simplified detection system has not yet been developed forSchizosaccharomyces pombe. In the present study, we describe a new vector system for the visualization of localized RNAs inS. pombeusing a U1A-tag-GFP system. A pREP1-U1A-tag vector plasmid to express U1A-tagged RNA and a pREP2-U1AGFP plasmid to produce a U1A-GFP fusion protein were constructed for this system. Since the U1A-GFP protein binds U1A-tagged RNA, fluorescence is observed at the location of U1A-tagged RNA in cells expressing both of these. The nucleolar localization of U3 snoRNA was successfully detected using this system, and a novel RNA localized at the DNA region of the nucleus was found by screening localized RNAs. This system will accelerate the study of localized RNAs inS. pombe. A, A simplified vector system for visualization of localized RNAs inS. pombe. B, A novel RNA localized in the DNA region of the nucleus, B1199, was found by screening. [ABSTRACT FROM AUTHOR]