title: Mlc1p promotes septum closure during cytokinesis via the IQ motifs of the vesicle motor Myo2p.
abstract: Little is known about the molecular machinery that directs secretory vesicles to the site of cell separation during cytokinesis. We show that in Saccharomyces cerevisiae, the class V myosin Myo2p and the Rab/Ypt Sec4p, that are required for vesicle polarization processes at all stages of the cell cycle, form a complex with each other and with a myosin light chain, Mlc1p, that is required for actomyosin ring assembly and cytokinesis. Mlc1p travels on secretory vesicles and forms a complex(es) with Myo2p and/or Sec4p. Its functional interaction with Myo2p is essential during cytokinesis to target secretory vesicles to fill the mother bud neck. The role of Mlc1p in actomyosin ring assembly instead is dispensable for this process. Therefore, in yeast, as recently shown in mammals, class V myosins associate with vesicles via the formation of a complex with Rab/Ypt proteins. Further more, myosin light chains, via their ability to be transported by secretory vesicles and to interact with class V myosin IQ motifs, can regulate vesicle polarization processes at a specific location and stage of the cell cycle.
authors.affiliation: Institute of Microbiology and Genetics, Vienna Biocenter, University of Vienna, Dr Bohrgasse 9, A-1030 Vienna, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wagner
authors.forename: Pamela
authors.initials: P
authors.lastname: Bielli
authors.forename: Stefan
authors.initials: S
authors.lastname: Wacha
authors.forename: Antonella
authors.initials: A
authors.lastname: Ragnini-Wilson
mesh_terms: D002455:Cell Division / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors; D018995:Myosin Heavy Chains / Q000378:metabolism*; D018994:Myosin Light Chains / Q000378:metabolism*; D024701:Myosin Type V / Q000378:metabolism*; D011233:Precipitin Tests; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000378:metabolism
chemical_list: D020662:Guanine Nucleotide Exchange Factors; C113979:MLC1 protein, S cerevisiae; C077512:MYO2 protein, S cerevisiae; D018994:Myosin Light Chains; C064456:SEC2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D019204:GTP-Binding Proteins; D024701:Myosin Type V; C064320:SEC4 protein, S cerevisiae; D018995:Myosin Heavy Chains; D020691:rab GTP-Binding Proteins