title: Molecular dissection of the checkpoint kinase Hsl1p.
abstract: Cell shape can influence cell behavior. In Saccharomyces cerevisiae, bud emergence can influence cell cycle progression via the morphogenesis checkpoint. This surveillance pathway ensures that mitosis always follows bud formation by linking degradation of the mitosis-inhibitory kinase Swe1p (Wee1) to successful bud emergence. A crucial component of this pathway is the checkpoint kinase Hsl1p, which is activated upon bud emergence and promotes Swe1p degradation. We have dissected the large nonkinase domain of Hsl1p by using evolutionary conservation as a guide, identifying regions important for Hsl1p localization, function, and regulation. An autoinhibitory motif restrains Hsl1p activity when it is not properly localized to the mother-bud neck. Hsl1p lacking this motif is active as a kinase regardless of the assembly state of cytoskeletal septin filaments. However, the active but delocalized Hsl1p cannot promote Swe1p down-regulation, indicating that localization is required for Hsl1p function as well as Hsl1p activation. We also show that the septin-mediated Hsl1p regulation via the novel motif operates in parallel to a previously identified Hsl1p activation pathway involving phosphorylation of the Hsl1p kinase domain. We suggest that Hsl1p responds to alterations in septin organization, which themselves occur in response to the local geometry of the cell cortex.
authors.affiliation: Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: John
authors.initials: J
authors.lastname: Crutchley
authors.forename: Kindra M
authors.initials: KM
authors.lastname: King
authors.forename: Mignon A
authors.initials: MA
authors.lastname: Keaton
authors.forename: Lee
authors.initials: L
authors.lastname: Szkotnicki
authors.forename: David A
authors.initials: DA
authors.lastname: Orlando
authors.forename: Trevin R
authors.initials: TR
authors.lastname: Zyla
authors.forename: Elaine S G
authors.initials: ES
authors.lastname: Bardes
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Lew
mesh_terms: D004789:Enzyme Activation; D010766:Phosphorylation; D010802:Phylogeny; D011485:Protein Binding; D011494:Protein Kinases / Q000737:chemistry* / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011484:Protein-Arginine N-Methyltransferases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism*; D017384:Sequence Deletion; D013329:Structure-Activity Relationship
chemical_list: D029701:Saccharomyces cerevisiae Proteins; D011484:Protein-Arginine N-Methyltransferases; C120666:HSL7 protein, S cerevisiae; D011494:Protein Kinases; C411302:ELM1 protein, S cerevisiae; C106494:HSL1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases