A masked NES in INI1/hSNF5 mediates hCRM1-dependent nuclear export: implications for tumorigenesis.
INI1 (integrase interactor 1)/hSNF5 is a component of the mammalian SWI/SNF complex and a tumor suppressor mutated in malignant rhabdoid tumors (MRT). We have identified a nuclear export signal (NES) in the highly conserved repeat 2 domain of INI1 that is unmasked upon deletion of a downstream sequence. Mutation of conserved hydrophobic residues within the NES, as well as leptomycin B treatment abrogated the nuclear export. Full-length INI1 specifically associated with hCRM1/exportin1 in vivo and in vitro. A mutant INI1 [INI1(1-319) delG950] found in MRT lacking the 66 C-terminal amino acids mislocalized to the cytoplasm. Full-length INI1 but not the INI1(1-319 delG950) mutant caused flat cell formation and cell cycle arrest in cell lines derived from MRT. Disruption of the NES in the delG950 mutant caused nuclear localization of the protein and restored its ability to cause cell cycle arrest. These observations demonstrate that INI1 has a masked NES that mediates regulated hCRM1/exportin1-dependent nuclear export and we propose that mutations that cause deregulated nuclear export of the protein could lead to tumorigenesis.
Craig
Errol
E
Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, New York, NY 10461, USA.
Zhang
Zhi-Kai
ZK
Davies
Kelvin P
KP
Kalpana
Ganjam V
GV
D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000502:physiology*; D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D002453:Cell Cycle; D048429:Cell Size / Q000235:genetics; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D002868:Chromosomal Proteins, Non-Histone; D004273:DNA, Neoplasm / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D028884:Karyopherins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018335:Rhabdoid Tumor / Q000209:etiology* / Q000235:genetics*; D000071796:SMARCB1 Protein; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors; D000097606:Exportin 1 Protein
D002868:Chromosomal Proteins, Non-Histone; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D005231:Fatty Acids, Unsaturated; D028884:Karyopherins; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D000071796:SMARCB1 Protein; D014157:Transcription Factors; D000097606:Exportin 1 Protein; C513266:SMARCB1 protein, human; C038753:leptomycin B