title: Human GTPases associate with RNA polymerase II to mediate its nuclear import.
abstract: Small GTPases share a biochemical mechanism and act as binary molecular switches. One important function of small GTPases in the cell is nucleocytoplasmic transport of both proteins and RNA. Here, we show the stable association of human GPN1 and GPN3, small GTPases related to Ran, with RNA polymerase II (RNAPII) isolated from either the cytoplasmic or nuclear fraction. GPN1 and GPN3 directly interact with RNAPII subunit 7 (RPB7)/RPB4 and the C-terminal domain (CTD) of RNAPII. Depletion of GPN1 or GPN3 using small interfering RNAs led to decreased RNAPII levels in the nucleus and an accumulation of this enzyme in the cytoplasm of human cells. Furthermore, isolation of a GPN1/GPN3/RNAPII complex from stable cell lines expressing a dominant negative GPN1 harboring mutations in the GTP-binding pocket demonstrated a role for these proteins in nuclear import of RNAPII. Thus, GPN1/GPN3 define a new family of small GTPases that are specialized for the transport of RNA polymerase II into the nucleus.
authors.affiliation: The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA. ccarre@wistar.org
authors.forename: Clément
authors.initials: C
authors.lastname: Carré
authors.forename: Ramin
authors.initials: R
authors.lastname: Shiekhattar
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D000595:Amino Acid Sequence; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D012319:RNA Polymerase II / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D046912:Multiprotein Complexes; D021122:Protein Subunits; D012319:RNA Polymerase II; D011993:Recombinant Fusion Proteins; C472669:GPN1 protein, human; C562157:GPN3 protein, human