Reversal of Xenopus Oct25 function by disruption of the POU domain structure.
Xenopus Oct25 is a POU family subclass V (POU-V) transcription factor with a distinct domain structure. To investigate the contribution of different domains to the function of Oct25, we have performed gain of function analyses. Deletions of the N- or C-terminal regions and of the Hox domain (except its nuclear localization signal) result in mutants being indistinguishable from the wild type protein in the suppression of genes promoting germ layer formation. Deletion of the complete POU domain generates a mutant that has no effect on embryogenesis. However, disruption of the alpha-helical structures in the POU domain, even by a single amino acid mutation, causes reversal of protein function. Overexpression of such mutants leads to dorsalization of embryos and formation of secondary axial structures. The underlying mechanism is an enhanced transcription of genes coding for antagonists of the ligands for ventralizing bone morphogenetic protein and Wnt pathways. Corresponding deletion mutants of Xenopus Oct60, Oct91, or mouse Oct4 also exhibit such a dominant-negative effect. Therefore, our results reveal that the integrity of the POU domain is crucial for the function of POU-V transcription factors in the regulation of genes that promote germ layer formation.
Cao
Ying
Y
Institute of Biochemistry, University of Ulm, D-89081 Ulm, Germany.
Oswald
Franz
F
Wacker
Stephan A
SA
Bundschu
Karin
K
Knöchel
Walter
W
D028341:Activins / Q000378:metabolism; D000818:Animals; D055415:Bone Morphogenetic Protein 4 / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D017353:Gene Deletion; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007668:Kidney / Q000166:cytology; D051379:Mice; D016296:Mutagenesis / Q000502:physiology; D055457:Nodal Protein / Q000378:metabolism; D019913:Nuclear Localization Signals / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D050814:Octamer Transcription Factor-3 / Q000378:metabolism; D050816:Octamer Transcription Factor-6 / Q000378:metabolism; D050809:POU Domain Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000502:physiology; D020825:T-Box Domain Proteins / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology; D014981:Xenopus / Q000196:embryology / Q000235:genetics*; D029867:Xenopus Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism
D055415:Bone Morphogenetic Protein 4; C495266:CTNNB1 protein, Xenopus; D055457:Nodal Protein; D019913:Nuclear Localization Signals; D050814:Octamer Transcription Factor-3; D050809:POU Domain Factors; D020825:T-Box Domain Proteins; C103966:VegT protein, Xenopus; D029867:Xenopus Proteins; D051176:beta Catenin; C525812:bmp4 protein, Xenopus; C527329:pou5f3.2 protein, Xenopus; D028341:Activins; D050816:Octamer Transcription Factor-6