[show abstract][hide abstract] ABSTRACT: The transcription factor Klf4 has demonstrated activity in the reprogramming of somatic cells to a pluripotent state, but the molecular mechanism of this process remains unknown. It is, therefore, of great interest to understand the functional role of Klf4 and related genes in ESC regulation. Here, we show that homozygous disruption of Klf5 results in the failure of ESC derivation from ICM cells and early embryonic lethality due to an implantation defect. Klf5 KO ESCs show increased expression of several differentiation marker genes and frequent, spontaneous differentiation. Conversely, overexpression of Klf5 in ESCs suppressed the expression of differentiation marker genes and maintained pluripotency in the absence of LIF. Our results also suggest that Klf5 regulates ESC proliferation by promoting phosphorylation of Akt1 via induction of Tcl1. These results, therefore, provide new insights into the functional and mechanistic role of Klf5 in regulation of pluripotency.
[show abstract][hide abstract] ABSTRACT: Rat BTEB2 protein is a transcription factor with three zinc fingers that binds to GC box, and is expressed in the placenta, intestine, and testis. To understand mechanisms of gene expression of BTEB2, we have cloned the rat BTEB2 gene from a rat liver genomic library and determined the gene structure. The BTEB2 gene contained 4 exons. In the process of cloning of the BTEB2 gene, we cloned two pseudogenes for BTEB2, one of which was a processed gene. The upstream region of the bona fide gene was fused to a luciferase reporter gene, and the generated BTEB2-luciferase chimeric plasmid was transiently transfected into HeLa cells that expressed endogenous BTEB2 mRNA. Significant expression of luciferase activity was observed. Deletion analysis of the promoter region of the BTEB2 gene revealed that at least three regions are important for the activity. Upon investigation of cis-acting elements in the regions, the GC box, CCAAT box and NF-1 binding site were found. As binding factors, Sp1, CBFa, and NF-1 were identified to the DNA elements by gel mobility shift assays using specific antibodies.