The human OCT-4 isoforms differ in their ability to confer self-renewal.
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.
Lee
Jungwoon
J
Laboratory of Molecular and Cellular Biology, Department of Life Science, Sogang University, Seoul 121-742, Korea.
Kim
Hye Kyoung
HK
Rho
Jeung-Yon
JY
Han
Yong-Mahn
YM
Kim
Jungho
J
D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D053595:Embryonic Stem Cells / Q000166:cytology / Q000378:metabolism; D006801:Humans; D051379:Mice; D050814:Octamer Transcription Factor-3 / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation / Q000235:genetics
D050814:Octamer Transcription Factor-3; D020033:Protein Isoforms; D004247:DNA