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Original Article |
Correspondence to: Kelly Tatchell, Department of Biochemistry and Molecular Biology, 1501 Kings Highway, Louisiana State University Medical Center, Shreveport, LA 71130. Tel:(318) 675-7769 Fax:(318) 675-5180 E-mail:ktatch{at}mail.sh.lsumc.edu.
Protein phosphatase type I (PP1), encoded by the single essential gene GLC7 in Saccharomyces cerevisiae, functions in diverse cellular processes. To identify in vivo subcellular location(s) where these processes take place, we used a functional green fluorescent protein (GFP)Glc7p fusion protein. Time-lapse fluorescence microscopy revealed GFPGlc7p localizes predominantly in the nucleus throughout the mitotic cell cycle, with the highest concentrations in the nucleolus. GFPGlc7p was also observed in a ring at the bud neck, which was dependent upon functional septins. Supporting a role for Glc7p in bud site selection, a glc7-129 mutant displayed a random budding pattern. In
-factor treated cells, GFPGlc7p was located at the base of mating projections, again in a septin-dependent manner. At the start of anaphase, GFPGlc7p accumulated at the spindle pole bodies and remained there until cytokinesis. After anaphase, GFPGlc7p became concentrated in a ring that colocalized with the actomyosin ring. A GFPGlc7-129 fusion was defective in localizing to the bud neck and SPBs. Together, these results identify sites of Glc7p function and suggest Glc7p activity is regulated through dynamic changes in its location.
Key Words: protein phosphatase type I, yeast, GLC7, cell cycle, green fluorescent protein
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