Differential roles of Sall4 isoforms in embryonic stem cell pluripotency.
Murine embryonic stem (ES) cells are defined by continuous self-renewal and pluripotency. A diverse repertoire of protein isoforms arising from alternative splicing is expressed in ES cells without defined biological roles. Sall4, a transcription factor essential for pluripotency, exists as two isoforms (Sall4a and Sall4b). Both isoforms can form homodimers and a heterodimer with each other, and each can interact with Nanog. By genomewide location analysis, we determined that Sall4a and Sall4b have overlapping, but not identical binding sites within the ES cell genome. In addition, Sall4b, but not Sall4a, binds preferentially to highly expressed loci in ES cells. Sall4a and Sall4b binding sites are distinguished by both epigenetic marks at target loci and their clustering with binding sites of other pluripotency factors. When ES cells expressing a single isoform of Sall4 are generated, Sall4b alone could maintain the pluripotent state, although it could not completely suppress all differentiation markers. Sall4a and Sall4b collaborate in maintenance of the pluripotent state but play distinct roles. Our work is novel in establishing such isoform-specific differences in ES cells.
Rao
Sridhar
S
Dana Farber Cancer Institute, Department of Pediatric Oncology, Boston, MA, USA.
Zhen
Shao
S
Roumiantsev
Sergei
S
McDonald
Lindsay T
LT
Yuan
Guo-Cheng
GC
Orkin
Stuart H
SH
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D044127:Epigenesis, Genetic; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051379:Mice; D046228:Microarray Analysis; D008969:Molecular Sequence Data; D000071317:Nanog Homeobox Protein; D039904:Pluripotent Stem Cells / Q000166:cytology / Q000502:physiology*; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D000071317:Nanog Homeobox Protein; C475540:Nanog protein, mouse; D020033:Protein Isoforms; C509167:Sall4 protein, mouse; D014157:Transcription Factors