Phenotypic Complementation Establishes Requirements for Specific POU Domain and Generic Transactivation Function of Oct-3/4 in Embryonic Stem Cells

• DOI: 10.1128/mcb.22.5.1526-1536.2002
• Publication Date: 2002-07-27T09:56:57Z
• Authors: Hitoshi Niwa; Shinji Masui; Ian Chambers; Austin G. Smith; Jun-ichi Miyazaki
• Keywords: Transcriptional Activation; 0301 basic medicine; Stem Cells; Genetic Complementation Test; Phenotypic Complementation; Embryo, Mammalian; Protein Structure, Tertiary; DNA-Binding Proteins; Mice; 03 medical and health sciences; Mutation; Animals; Humans; Embryonic; gene; Octamer Transcription Factor-3; Cells, Cultured; Protein Binding; Sequence Deletion; Transcription Factors

Transcription factors of the POU family govern cell fate through combinatorial interactions with coactivators and corepressors. The POU factor Oct-3/4 can define differentiation, dedifferentation, or self-renewal of pluripotent embryonic stem (ES) cells in a sensitive, dose-dependent manner (H. Niwa, J.-I. Miyazali, and A. G. Smith, Nat. Genet. 24:372-376, 2000). Here we have developed a complementation assay based on the ability of Oct-3/4 transgenes to rescue self-renewal in conditionally null ES cells and used this to define which domains of Oct-3/4 are required to sustain the undifferentiated stem cell phenotype. Surprisingly, we found that molecules lacking either the N-terminal or C-terminal transactivation domain, though not both, can effectively replace full-length Oct-3/4. Furthermore, a fusion of the heterologous transactivation domain of Oct-2 to the Oct-3/4 POU domain can also sustain self-renewal. Thus, the unique function of Oct-3/4 in ES cell propagation resides in combination of the specific POU domain with a generic proline-rich transactivation domain. Interestingly, however, Oct-3/4 target gene expression elicited by the N- and C-terminal transactivation domains is not identical, indicating that at least one class of genes activated by Oct-3/4 is not required for ES cell propagation.