The cytosolic protein G0S2 maintains quiescence in hematopoietic stem cells.
Bone marrow hematopoietic stem cells (HSCs) balance proliferation and differentiation by integrating complex transcriptional and post-translational mechanisms regulated by cell intrinsic and extrinsic factors. We found that transcripts of G(0)/G(1) switch gene 2 (G0S2) are enriched in lineage(-) Sca-1(+) c-kit(+) (LSK) CD150(+) CD48(-) CD41(-) cells, a population highly enriched for quiescent HSCs, whereas G0S2 expression is suppressed in dividing LSK CD150(+) CD48(-) cells. Gain-of-function analyses using retroviral expression vectors in bone marrow cells showed that G0S2 localizes to the mitochondria, endoplasmic reticulum, and early endosomes in hematopoietic cells. Co-transplantation of bone marrow cells transduced with the control or G0S2 retrovirus led to increased chimerism of G0S2-overexpressing cells in femurs, although their contribution to the blood was reduced. This finding was correlated with increased quiescence in G0S2-overexpressing HSCs (LSK CD150(+) CD48(-)) and progenitor cells (LS(-)K). Conversely, silencing of endogenous G0S2 expression in bone marrow cells increased blood chimerism upon transplantation and promoted HSC cell division, supporting an inhibitory role for G0S2 in HSC proliferation. A proteomic study revealed that the hydrophobic domain of G0S2 interacts with a domain of nucleolin that is rich in arginine-glycine-glycine repeats, which results in the retention of nucleolin in the cytosol. We showed that this cytosolic retention of nucleolin occurs in resting, but not proliferating, wild-type LSK CD150(+) CD48(-) cells. Collectively, we propose a novel model of HSC quiescence in which elevated G0S2 expression can sequester nucleolin in the cytosol, precluding its pro-proliferation functions in the nucleolus.
Department of Pathology & Immunology, Baylor College of Medicine, Texas Children's Hospital, Houston, Texas, United States of America.
Takeshi
T
Yamada
Chun Shik
CS
Park
Audrea
A
Burns
Daisuke
D
Nakada
H Daniel
HD
Lacorazza
D000818:Animals; D001773:Blood Cells / Q000378:metabolism; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000378:metabolism*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D051379:Mice; D041681:NIH 3T3 Cells; D010750:Phosphoproteins / Q000378:metabolism; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000378:metabolism; D012261:Ribonucleoproteins / Q000378:metabolism; D000097796:Nucleolin
D018797:Cell Cycle Proteins; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D000097796:Nucleolin; C508072:G0S2 protein, mouse