GNL3L Is a Nucleo-Cytoplasmic Shuttling Protein: Role in Cell Cycle Regulation.
GNL3L is an evolutionarily conserved high molecular weight GTP binding nucleolar protein belonging to HSR1-MMR1 subfamily of GTPases. The present investigation reveals that GNL3L is a nucleo-cytoplasmic shuttling protein and its export from the nucleus is sensitive to Leptomycin B. Deletion mutagenesis reveals that the C-terminal domain (amino acids 501-582) is necessary and sufficient for the export of GNL3L from the nucleus and the exchange of hydrophobic residues (M567, L570 and 572) within the C-terminal domain impairs this process. Results from the protein-protein interaction analysis indicate that GNL3L interaction with CRM1 is critical for its export from the nucleus. Ectopic expression of GNL3L leads to lesser accumulation of cells in the 'G2/M' phase of cell cycle whereas depletion of endogenous GNL3L results in 'G2/M' arrest. Interestingly, cell cycle analysis followed by BrdU labeling assay indicates that significantly increased DNA synthesis occurs in cells expressing nuclear export defective mutant (GNL3L∆NES) compared to the wild type or nuclear import defective GNL3L. Furthermore, increased hyperphosphorylation of Rb at Serine 780 and the upregulation of E2F1, cyclins A2 and E1 upon ectopic expression of GNL3L∆NES results in faster 'S' phase progression. Collectively, the present study provides evidence that GNL3L is exported from the nucleus in CRM1 dependent manner and the nuclear localization of GNL3L is important to promote 'S' phase progression during cell proliferation.
Laboratory of Molecular Virology and Cell Biology, Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology-Madras, Chennai, 600 036, India.
Indu Jose
IJ
Thoompumkal
Laboratory of Molecular Virology and Cell Biology, Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology-Madras, Chennai, 600 036, India.
Malireddi Rama Krishna
MR
Subba Rao
Laboratory of Molecular Virology and Cell Biology, Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology-Madras, Chennai, 600 036, India; National Cancer Tissue Biobank, Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology-Madras, Chennai, 600 036, India.
Anbarasu
A
Kumaraswamy
Laboratory of Molecular Virology and Cell Biology, Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology-Madras, Chennai, 600 036, India.
Rehna
R
Krishnan
Laboratory of Molecular Virology and Cell Biology, Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology-Madras, Chennai, 600 036, India; National Cancer Tissue Biobank, Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology-Madras, Chennai, 600 036, India.
Sundarasamy
S
Mahalingam
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D019556:COS Cells; D002455:Cell Division / Q000502:physiology*; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D002522:Chlorocebus aethiops; D056751:Cyclin A2 / Q000096:biosynthesis / Q000235:genetics; D019927:Cyclin E / Q000096:biosynthesis / Q000235:genetics; D050687:E2F1 Transcription Factor / Q000096:biosynthesis / Q000235:genetics; D016195:G2 Phase / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D056945:Hep G2 Cells; D006801:Humans; D061986:MCF-7 Cells; D051379:Mice; D016296:Mutagenesis; D041681:NIH 3T3 Cells; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D015513:Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics; D015854:Up-Regulation / Q000502:physiology
C503721:CCNA2 protein, human; C475820:CCNE1 protein, human; D056751:Cyclin A2; D019927:Cyclin E; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; C509155:GNL3L protein, human; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D019204:GTP-Binding Proteins