title: Identification of interphase functions for the NIMA kinase involving microtubules and the ESCRT pathway.
abstract: The Never in Mitosis A (NIMA) kinase (the founding member of the Nek family of kinases) has been considered a mitotic specific kinase with nuclear restricted roles in the model fungus Aspergillus nidulans. By extending to A. nidulans the results of a synthetic lethal screen performed in Saccharomyces cerevisiae using the NIMA ortholog KIN3, we identified a conserved genetic interaction between nimA and genes encoding proteins of the Endosomal Sorting Complex Required for Transport (ESCRT) pathway. Absence of ESCRT pathway functions in combination with partial NIMA function causes enhanced cell growth defects, including an inability to maintain a single polarized dominant cell tip. These genetic insights suggest NIMA potentially has interphase functions in addition to its established mitotic functions at nuclei. We therefore generated endogenously GFP-tagged NIMA (NIMA-GFP) which was fully functional to follow its interphase locations using live cell spinning disc 4D confocal microscopy. During interphase some NIMA-GFP locates to the tips of rapidly growing cells and, when expressed ectopically, also locates to the tips of cytoplasmic microtubules, suggestive of non-nuclear interphase functions. In support of this, perturbation of NIMA function either by ectopic overexpression or through partial inactivation results in marked cell tip growth defects with excess NIMA-GFP promoting multiple growing cell tips. Ectopic NIMA-GFP was found to locate to the plus ends of microtubules in an EB1 dependent manner, while impairing NIMA function altered the dynamic localization of EB1 and the cytoplasmic microtubule network. Together, our genetic and cell biological analyses reveal novel non-nuclear interphase functions for NIMA involving microtubules and the ESCRT pathway for normal polarized fungal cell tip growth. These insights extend the roles of NIMA both spatially and temporally and indicate that this conserved protein kinase could help integrate cell cycle progression with polarized cell growth.
authors.affiliation: Molecular, Cellular and Developmental Biology Program, The Ohio State University, Columbus, Ohio, United States of America; Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America.
authors.forename: Meera
authors.initials: M
authors.lastname: Govindaraghavan
authors.affiliation: Millsaps College, Jackson, Mississippi, United States of America.
authors.forename: Sarah Lea
authors.initials: SL
authors.lastname: McGuire Anglin
authors.affiliation: Molecular, Cellular and Developmental Biology Program, The Ohio State University, Columbus, Ohio, United States of America; Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America.
authors.forename: Kuo-Fang
authors.initials: KF
authors.lastname: Shen
authors.affiliation: Molecular, Cellular and Developmental Biology Program, The Ohio State University, Columbus, Ohio, United States of America; Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio, United States of America.
authors.forename: Nandini
authors.initials: N
authors.lastname: Shukla
authors.affiliation: Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America.
authors.forename: Colin P
authors.initials: CP
authors.lastname: De Souza
authors.affiliation: Molecular, Cellular and Developmental Biology Program, The Ohio State University, Columbus, Ohio, United States of America; Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America; Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio, United States of America.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Osmani
mesh_terms: D001233:Aspergillus nidulans / Q000235:genetics; D002453:Cell Cycle / Q000235:genetics; D018797:Cell Cycle Proteins / Q000235:genetics*; D002467:Cell Nucleus / Q000235:genetics; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics* / Q000378:metabolism; D049452:Green Fluorescent Proteins; D007399:Interphase / Q000235:genetics*; D008870:Microtubules / Q000235:genetics*; D008938:Mitosis / Q000235:genetics; D000072380:NIMA-Related Kinase 1; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*
chemical_list: D018797:Cell Cycle Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D049452:Green Fluorescent Proteins; D000072380:NIMA-Related Kinase 1; D017346:Protein Serine-Threonine Kinases