title: Cyclin-dependent kinase-mediated Sox2 phosphorylation enhances the ability of Sox2 to establish the pluripotent state.
abstract: Sox2 is a key factor in maintaining self-renewal of embryonic stem cells (ESCs) and adult stem cells as well as in reprogramming differentiated cells back into pluripotent or multipotent stem cells. Although previous studies have shown that Sox2 is phosphorylated in human ESCs, the biological significance of Sox2 phosphorylation in ESC maintenance and reprogramming has not been well understood. In this study we have identified new phosphorylation sites on Sox2 and have further demonstrated that Cdk2-mediated Sox2 phosphorylation at Ser-39 and Ser-253 is required for establishing the pluripotent state during reprogramming but is dispensable for ESC maintenance. Mass spectrometry analysis of purified Sox2 protein has identified new phosphorylation sites on two tyrosine and six serine/Threonine residues. Cdk2 physically interacts with Sox2 and phosphorylates Sox2 at Ser-39 and Ser-253 in vitro. Surprisingly, Sox2 phosphorylation at Ser-39 and Ser-253 is dispensable for ESC self-renewal and cell cycle progression. In addition, Sox2 phosphorylation enhances its ability to establish the pluripotent state during reprogramming by working with Oct4 and Klf4. Finally, Cdk2 can also modulate the ability of Oct4, Sox2, and Klf4 in reprogramming fibroblasts back into pluripotent stem cells. Therefore, this study has for the first time demonstrated that Sox2 phosphorylation by Cdk2 promotes the establishment but not the maintenance of the pluripotent state. It might also help explain why the inactivation of CDK inhibitors such as p53, p21, and Arf/Ink4 promotes the induction of pluripotent stem cells.
authors.affiliation: From the Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China, Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, 510530 Guangzhou, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Ouyang
authors.affiliation: Stowers Institute for Medical Research, Kansas City, Missouri 64110.
authors.forename: Wei
authors.initials: W
authors.lastname: Yu
authors.affiliation: Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, 510530 Guangzhou, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.affiliation: Stowers Institute for Medical Research, Kansas City, Missouri 64110.
authors.forename: Nian
authors.initials: N
authors.lastname: Zhang
authors.affiliation: Stowers Institute for Medical Research, Kansas City, Missouri 64110.
authors.forename: Laurence
authors.initials: L
authors.lastname: Florens
authors.affiliation: Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, 510530 Guangzhou, China.
authors.forename: Jiekai
authors.initials: J
authors.lastname: Chen
authors.affiliation: Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, 510530 Guangzhou, China.
authors.forename: He
authors.initials: H
authors.lastname: Liu
authors.affiliation: Stowers Institute for Medical Research, Kansas City, Missouri 64110, Department of Pathology and Laboratory Medicine, The University of Kansas Medical Center, Kansas City, Kansas 66160, and.
authors.forename: Michael
authors.initials: M
authors.lastname: Washburn
authors.affiliation: Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, 510530 Guangzhou, China, pei_duanqing@gibh.ac.cn.
authors.forename: Duanqing
authors.initials: D
authors.lastname: Pei
authors.affiliation: Stowers Institute for Medical Research, Kansas City, Missouri 64110, Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, Kansas 66160 tgx@stowers.org.
authors.forename: Ting
authors.initials: T
authors.lastname: Xie
mesh_terms: D000818:Animals; D002460:Cell Line; D000067470:Cellular Reprogramming Techniques; D051357:Cyclin-Dependent Kinase 2 / Q000235:genetics / Q000378:metabolism*; D053595:Embryonic Stem Cells / Q000378:metabolism*; D006801:Humans; D057026:Induced Pluripotent Stem Cells / Q000378:metabolism*; D000090062:Kruppel-Like Factor 4; D051379:Mice; D010766:Phosphorylation / Q000235:genetics; D055748:SOXB1 Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C000715467:KLF4 protein, human; C000715468:Klf4 protein, mouse; D000090062:Kruppel-Like Factor 4; C527782:SOX2 protein, human; D055748:SOXB1 Transcription Factors; C527783:Sox2 protein, mouse; C495894:CDK2 protein, human; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2
keywords: cell cycle; cyclin-dependent kinase (CDK); induced pluripotent stem cell (iPS cell) (iPSC); phosphorylation; pluripotency; protein phosphorylation; reprograming; reprogramming; self-renewal