C3G shows regulated nucleocytoplasmic exchange and represses histone modifications associated with euchromatin.
C3G (RapGEF1) is a ubiquitously expressed guanine nucleotide exchange factor that functions in signaling pathways regulating cell proliferation, apoptosis, and actin reorganization. It is essential for differentiation and early embryonic development in mice. Overexpressed C3G shows predominant cytoplasmic localization, but endogenous C3G is a component of nuclear fractions in a variety of cell types. Coexpression of importin-α and inhibition of nuclear export by leptomycin B resulted in predominant nuclear localization of C3G. Functional NLSs, NES, and GSK3-β-dependent phosphorylation regulate its dynamic nuclear localization. C3G translocates to the nucleus in response to myogenic differentiation and sublethal dose of cisplatin. C3G is associated with chromatin and nuclear matrix fractions. Cells with C3G localized in the nucleus showed peripheralization of heterochromatin and reduced histone modifications associated with euchromatin. Short hairpin RNA-mediated depletion of C3G in epithelial cells resulted in reduced expression of CDK inhibitors and the histone demethylase KDM5A. Myoblast clones with CRISPR/Cas9-mediated knockout of C3G failed to show repression of histone marks and did not show up-regulation of myosin heavy chain and myotube formation when grown in differentiation medium. Our results document regulated nucleocytoplasmic exchange of C3G in response to physiological stimuli and provide insights into nuclear functions for C3G.
Centre for Cellular and Molecular Biology, Hyderabad 500 007, India.
Dhruv Kumar
DK
Shakyawar
Centre for Cellular and Molecular Biology, Hyderabad 500 007, India.
Kunal
K
Dayma
Centre for Cellular and Molecular Biology, Hyderabad 500 007, India.
Anesh
A
Ramadhas
Centre for Cellular and Molecular Biology, Hyderabad 500 007, India.
Chavvakula
C
Varalakshmi
Centre for Cellular and Molecular Biology, Hyderabad 500 007, India vradha@ccmb.res.in.
Vegesna
V
Radha
D000199:Actins / Q000378:metabolism; D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D022041:Euchromatin / Q000378:metabolism / Q000502:physiology*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D020735:Guanine Nucleotide-Releasing Factor 2 / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D042421:Histone Code / Q000502:physiology*; D051379:Mice; D024510:Muscle Development; D019913:Nuclear Localization Signals; D010766:Phosphorylation; D015398:Signal Transduction; D015854:Up-Regulation
D000199:Actins; D022041:Euchromatin; D005231:Fatty Acids, Unsaturated; D020662:Guanine Nucleotide Exchange Factors; D020735:Guanine Nucleotide-Releasing Factor 2; D019913:Nuclear Localization Signals; D038362:Glycogen Synthase Kinase 3; C038753:leptomycin B