title: The anillin-related region of Bud4 is the major functional determinant for Bud4's function in septin organization during bud growth and axial bud site selection in budding yeast.
abstract: The anillin-related protein Bud4 of Saccharomyces cerevisiae is required for axial bud site selection by linking the axial landmark to the septins, which localize at the mother bud neck. Recent studies indicate that Bud4 plays a role in septin organization during cytokinesis. Here we show that Bud4 is also involved in septin organization during bud growth prior to cytokinesis, as bud4Δ shs1Δ cells displayed an elongated bud morphology and defective septin organization at 18°C. Bud4 overexpression also affected septin organization during bud growth in shs1Δ cells at 30°C. Bud4 was previously thought to associate with the septins via its central region, while the C-terminal anillin-related region was not involved in septin association. Surprisingly, we found that the central region of Bud4 alone targets to the bud neck throughout the cell cycle, unlike full-length Bud4, which localizes to the bud neck only during G2/M phase. We identified the anillin-related region to be a second targeting domain that cooperates with the central region for proper septin association. In addition, the anillin-related region could largely mediate Bud4's function in septin organization during bud growth and bud site selection. We show that this region interacts with the C terminus of Bud3 and the two segments depend on each other for association with the septins. Moreover, like the bud4Δ mutant, the bud3Δ mutant genetically interacts with shs1Δ and cdc12-6 mutants in septin organization, suggesting that Bud4 and Bud3 may cooperate in septin organization during bud growth. These observations provide new insights into the interaction of Bud4 with the septins and Bud3.
authors.affiliation: Department of Microbiology, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Huan
authors.initials: H
authors.lastname: Wu
authors.affiliation: Department of Microbiology, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Guo
authors.affiliation: Department of Microbiology, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Ya-Ting
authors.initials: YT
authors.lastname: Zhou
authors.affiliation: Department of Microbiology, College of Life Sciences, Wuhan University, Wuhan, China Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Wuhan, China xdgao@whu.edu.cn.
authors.forename: Xiang-Dong
authors.initials: XD
authors.lastname: Gao
mesh_terms: D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division; D003285:Contractile Proteins / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D058112:Septins / Q000378:metabolism*
chemical_list: C093319:BUD3 protein, S cerevisiae; C100763:BUD4 protein, S cerevisiae; D018797:Cell Cycle Proteins; D003285:Contractile Proteins; C115656:SHS1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C095886:anillin; D019204:GTP-Binding Proteins; D058112:Septins