Rex-1, a Gene Encoding a Transcription Factor Expressed in the Early Embryo, Is Regulated via Oct-3/4 and Oct-6 Binding to an Octamer Site and a Novel Protein, Rox-1, Binding to an Adjacent Site

Abstract

The Rex-1 (Zfp-42) gene, which encodes an acidic zinc finger protein, is expressed at high levels in embryonic stem (ES) and F9 teratocarcinoma cells. Prior analysis identified an octamer motif in the Rex-1 promoter which is required for promoter activity in undifferentiated F9 cells and is involved in retinoic acid (RA)-associated reduction in expression. We show here that the Oct-3/4 transcription factor, but not Oct-1, can either activate or repress the Rex-1 promoter, depending on the cellular environment. Rex-1 repression is enhanced by E1A. The protein domain required for Oct-3/4 activation was mapped to amino acids 1 to 35, whereas the domain required for Oct-3/4 repression was mapped to amino acids 61 to 126, suggesting that the molecular mechanisms underlying transcriptional activation and repression differ. Like Oct-3/4, Oct-6 can also lower the expression of the Rex-1 promoter via the octamer site, and the amino-terminal portion of Oct-6 mediates this repression. In addition to the octamer motif, a novel positive regulatory element, located immediately 5 of the octamer motif, was identified in the Rex-1 promoter. Mutations in this element greatly reduce Rex-1 promoter activity in F9 cells. High levels of a binding protein(s), designated Rox-1, recognize this novel DNA element in F9 cells, and this binding activity is reduced following RA treatment. Taken together, these results indicate that the Rex-1 promoter is regulated by specific octamer family members in early embryonic cells and that a novel element also contributes to Rex-1 expression.

Promotion of self-renewal of embryonic stem cells by midkine

“…Nanog overexpression is sufficient for the self-renewal of mESCs in the absence of LIF [40] . Sox2 synergizes with Oct3/4 to activate transcription of target genes such as Fgf4 and Rex1 [36,41] . Extrinsic and intrinsic factors co-operate to form a complex network that regulates the pluripotency of ESCs.…”

A Unique Developmental Pattern of Oct-3/4DNA Methylation Is Controlled by a cis-demodification Element

“…Both plasmids behaved similarly to each other. As shown previously (8,26,30), the unmethylated plasmids drive efficient transcription when transiently transfected into P19 cells. Transfectants containing the HhaI-methylated plasmids show a slightly reduced level of luciferase activity.…”

“…Whole Cell Extracts (WCEs)-WCEs and electrophoretic mobility shift assays (EMSAs) were done as described previously (30). 1Awt and mut1A oligonucleotides (described in Table III) were used for EMSAs.…”

Epithelial Colonies Cultured from Human Explanted Liver in Subacute Hepatic Failure Exhibit Hepatocyte, Biliary Epithelial, and Stem Cell Phenotypic Markers

“…The Rex-1 promoter contains an octamer motif (ATTTCGAT at -220) that is the binding site for transcription factors of the POU domain family, including Oct-4, which can activate or repress Rex-1 depending upon the level of expression. The lack of Rex-1 expression in these cells may indicate that the levels of Oct-4 were sufficient to repress rather than activate Rex-1 [33].…”

“…The stem cell transcription factor Oct-4 in the mouse is restricted to the embryonic carcinoma and ES cells and becomes downregulated on subsequent differentiation [33]. We used this as a putative stem cell marker and noted its expression both early and late in the culture period and demonstrated its coexpression with markers of fully differentiated cells.…”