Identification and functional characterization of an alternative splice variant within the fourth exon of human nanog.
Nanog, a homeodomain (HD) transcription factor, plays a critical role in the maintenance of embryonic stem (ES) cell self-renewal. Here, we report the identification of an alternatively-spliced variant of nanog. This variant lacked a stretch of amino acids (residues 168-183) located between the HD and tryptophan-repeat (WR) of the previously-reported full length sequence, suggesting that the deleted sequence functions as a linker and possibly affects the flexibility of the C-terminal transactivation domain relative to the DNA binding domain. Expression of mRNA encoding the splice variant, designated as nanog-delta 48, was much lower than that of the full length version in human ES cells. The ratio of nanog-delta 48 transcript to full length transcript increased, however, in multipotent adult progenitor cells. EMSA analysis revealed that both forms of Nanog were able to bind a nanog binding sequence with roughly the same affinity. A reporter plasmid assay also showed that both variants of nanog modestly repressed transactivation of gata-4, whose expression is proposed to be inhibited by nanog, with comparable potency. We conclude that, despite the difference in primary structure and expression pattern in various stem cells, the alternatively-spliced variant of Nanog has similar activity to that of the full length version.
Kim
Jung Sun
JS
Division of Molecular and Life Sciences, College of Science and Technology, Hanyang University, Seoul 133-791, Korea.
Kim
Jiha
J
Kim
Byung Soo
BS
Chung
Hee Yong
HY
Lee
Young Yiul
YY
Park
Choon Sik
CS
Lee
Young Seek
YS
Lee
Young Han
YH
Chung
Il Yup
IY
D017398:Alternative Splicing / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D002467:Cell Nucleus; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005091:Exons / Q000235:genetics*; D050991:GATA4 Transcription Factor / Q000378:metabolism; D020869:Gene Expression Profiling; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D000071317:Nanog Homeobox Protein; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection
D004268:DNA-Binding Proteins; D050991:GATA4 Transcription Factor; D018398:Homeodomain Proteins; C486780:NANOG protein, human; D000071317:Nanog Homeobox Protein; D012333:RNA, Messenger