title: Serine 111 phosphorylation regulates OCT4A protein subcellular distribution and degradation.
abstract: Embryonic stem cell self-renewal properties are attributed to critical amounts of OCT4A, but little is known about its post-translational regulation. Sequence analysis revealed that OCT4A contains five putative ERK1/2 phosphorylation sites. Consistent with the hypothesis that OCT4A is a putative ERK1/2 substrate, we demonstrate that OCT4A interacts with ERK1/2 by using both in vitro GST pulldown and in vivo co-immunoprecipitation assays. MS analysis identified phosphorylation of OCT4A at Ser-111. To investigate the possibility that ERK1/2 activation can enhance OCT4A degradation, we analyzed endogenous ubiquitination in cells transfected with FLAG-OCT4A alone or with constitutively active MEK1 (MEK1(CA)), and we observed that the extent of OCT4 ubiquitination was clearly increased when MEK1(CA) was coexpressed and that this increase was more evident after MG132 treatment. These results suggest an increase in OCT4A ubiquitination downstream of MEK1 activation, and this could account for the protein loss observed after FGF2 treatment and MEK1(CA) transfection. Understanding and controlling the mechanism by which stem cells balance self-renewal would substantially advance our knowledge of stem cells.
authors.affiliation: Department of Medical and Biological Sciences, University of Udine, 33100 Udine, Italy. renzaspelat@yahoo.it
authors.forename: Renza
authors.initials: R
authors.lastname: Spelat
authors.forename: Federico
authors.initials: F
authors.lastname: Ferro
authors.forename: Francesco
authors.initials: F
authors.lastname: Curcio
mesh_terms: D045744:Cell Line, Tumor; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D018398:Homeodomain Proteins / Q000235:genetics; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D051741:Kruppel-Like Transcription Factors / Q000235:genetics; D007976:Leupeptins / Q000494:pharmacology; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D008856:Microscopy, Fluorescence; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000071317:Nanog Homeobox Protein; D050814:Octamer Transcription Factor-3 / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D059748:Proteolysis; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055748:SOXB1 Transcription Factors / Q000235:genetics; D012694:Serine / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D005419:Flavonoids; D018398:Homeodomain Proteins; D051741:Kruppel-Like Transcription Factors; D007976:Leupeptins; C486780:NANOG protein, human; D000071317:Nanog Homeobox Protein; D050814:Octamer Transcription Factor-3; C494173:POU5F1 protein, human; D020033:Protein Isoforms; C527782:SOX2 protein, human; D055748:SOXB1 Transcription Factors; C507976:ZFP42 protein, human; D016222:Fibroblast Growth Factor 2; D012694:Serine; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one