title: Rho GTPase-independent regulation of mitotic progression by the RhoGEF Net1.
abstract: Neuroepithelial transforming gene 1 (Net1) is a RhoA-subfamily-specific guanine nucleotide exchange factor that is overexpressed in multiple human cancers and is required for proliferation. Molecular mechanisms underlying its role in cell proliferation are unknown. Here we show that overexpression or knockdown of Net1 causes mitotic defects. Net1 is required for chromosome congression during metaphase and generation of stable kinetochore microtubule attachments. Accordingly, inhibition of Net1 expression results in spindle assembly checkpoint activation. The ability of Net1 to control mitosis is independent of RhoA or RhoB activation, as knockdown of either GTPase does not phenocopy effects of Net1 knockdown on nuclear morphology, and effects of Net1 knockdown are effectively rescued by expression of catalytically inactive Net1. We also observe that Net1 expression is required for centrosomal activation of p21-activated kinase and its downstream kinase Aurora A, which are critical regulators of centrosome maturation and spindle assembly. These results identify Net1 as a novel regulator of mitosis and indicate that altered expression of Net1, as occurs in human cancers, may adversely affect genomic stability.
authors.affiliation: Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, TX 77008, USA.
authors.forename: Sarita
authors.initials: S
authors.lastname: Menon
authors.forename: Wonkyung
authors.initials: W
authors.lastname: Oh
authors.forename: Heather S
authors.initials: HS
authors.lastname: Carr
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Frost
mesh_terms: D064096:Aurora Kinase A / Q000378:metabolism; D045744:Cell Line, Tumor; D020090:Chromosome Segregation; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D042822:Genomic Instability; D006367:HeLa Cells; D006801:Humans; D008870:Microtubules / Q000737:chemistry* / Q000378:metabolism; D008938:Mitosis / Q000235:genetics / Q000502:physiology*; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D054462:p21-Activated Kinases / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism; D020743:rhoB GTP-Binding Protein / Q000378:metabolism
chemical_list: C099763:NET1 protein, human; D015513:Oncogene Proteins; D064096:Aurora Kinase A; C515907:PAK2 protein, human; D054462:p21-Activated Kinases; D020742:rhoA GTP-Binding Protein; D020743:rhoB GTP-Binding Protein