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J Biol Chem. 2006 Nov 3;281(44):33554-65. Epub 2006 Sep 1.

The human OCT-4 isoforms differ in their ability to confer self-renewal.

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  • 1Laboratory of Molecular and Cellular Biology, Department of Life Science, Sogang University, Seoul 121-742, Korea.

Abstract

OCT-4 transcription factors play an important role in maintaining the pluripotent state of embryonic stem cells and may prevent expression of genes activated during differentiation. Human OCT-4 isoform mRNAs encode proteins that have identical POU DNA binding domains and C-terminal domains but differ in their N-terminal domains. We report here the cloning and characterization of the human OCT-4B isoform. Human OCT-4B cDNA encodes a 265-amino acid protein with a predicted molecular mass of 30 kDa. Embryonic stem (ES) cell-based complementation assays using ZHBTc4 ES cells showed that unlike human OCT-4A, OCT-4B cannot sustain ES cell self-renewal. In addition, OCT-4B does not bind to a probe carrying the OCT-4 consensus binding sequence, and we demonstrate that two separate regions of its N-terminal domain are responsible for inhibiting DNA binding. We also demonstrate that OCT-4B is mainly localized to the cytoplasm. Overexpression of OCT-4B did not activate transcription from OCT-4-dependent promoters, although OCT-4A did as reported previously. Furthermore, transcriptional activation by human OCT-4A was not inhibited by co-expression of OCT-4B. Taken together, these data suggest that the DNA binding, transactivation, and abilities to confer self-renewal of the human OCT-4 isoforms differ.

PMID:
16951404
[PubMed - indexed for MEDLINE]
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