Fig. 2.

Mechanisms of transcriptional regulation by HBP1. HBP1 is mainly characterized as a transcriptional repressor, which sequesters other transcription factors, such as LEF, TCF4 or MYC (a), or directly represses gene expression by recruiting cofactors such as HDAC or Sin3 (b). HBP1 can also directly activate the transcription of genes, for instance CDKN2A, by recruiting CBP/p300 (c). HBP1 was reported to stabilize p53 by preventing its degradation by the MDM2 ligase, resulting in upregulation of the p53 target gene CDKN1A (D). Finally, by lowering the expression of DNMT1 and EZH2, HBP1 prevents the deposition of repressive epigenetic marks (methylation of DNA and histone H3K27, respectively), thereby increasing the expression of target genes (e). See text for details