Possible regulation of Oct60 transcription by a positive feedback loop in Xenopus oocytes.

The POU family subclass V (POU-V) proteins have important roles in maintaining cells in an undifferentiated state. In Xenopus, expression of the POU-V protein Oct60 was detected in oocytes and was found to decrease in blastula- to gastrula-stage embryos. In addition, Oct60 overexpression inhibits some signals in early embryogenesis, including Activin/Nodal, BMP, and Wnt signalling. In this report, we analysed mechanisms of Oct60 promoter activation and discovered that Oct60 transcription was activated ectopically in somatic nuclei by oocyte extract treatment. Promoter assays demonstrated that Oct60 transcription was activated in oocytes specifically and that this activation was dependent on an Octamer-Sox binding motif. ChIP assays showed that the Oct60 protein binds the motif. These results suggest that Oct60 transcription is regulated by a positive-feedback loop in Xenopus oocytes.