title: The pluripotency rheostat Nanog functions as a dimer.
abstract: The defining activity of the homeodomain protein Nanog is the ability to confer cytokine-independent self-renewal upon ES (embryonic stem) cells in which it is overexpressed. However, the biochemical basis by which Nanog achieves this function remains unknown. In the present study, we show that Nanog dimerizes through a functionally critical domain. Co-immunoprecipitation of Nanog molecules tagged with distinct epitopes demonstrates that Nanog self-associates through a region in which every fifth residue is tryptophan. In vitro binding experiments establish that this region participates directly in self-association. Moreover, analytical ultracentrifugation indicates that, in solution, Nanog is in equilibrium between monomeric and dimeric forms with a K(d) of 3 muM. The functional importance of Nanog dimerization is established by ES cell colony-forming assays in which deletion of the tryptophan-repeat region eliminates the capacity of Nanog to direct LIF (leukaemia inhibitory factor)-independent self-renewal.
authors.affiliation: MRC Centre Development in Stem Cell Biology, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JQ, U.K.
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Mullin
authors.forename: Adam
authors.initials: A
authors.lastname: Yates
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Rowe
authors.forename: Bianca
authors.initials: B
authors.lastname: Nijmeijer
authors.forename: Douglas
authors.initials: D
authors.lastname: Colby
authors.forename: Paul N
authors.initials: PN
authors.lastname: Barlow
authors.forename: Malcolm D
authors.initials: MD
authors.lastname: Walkinshaw
authors.forename: Ian
authors.initials: I
authors.lastname: Chambers
mesh_terms: D000818:Animals; D016207:Cytokines / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D000071317:Nanog Homeobox Protein; D011485:Protein Binding; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D016207:Cytokines; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D000071317:Nanog Homeobox Protein; C475540:Nanog protein, mouse; D011994:Recombinant Proteins