Fig. 6.

HoxC5 represses hTERT expression through its binding to hTERT upstream enhancer region. a ChIP-Seq results indicate the binding of HoxC5 and Pbx4 at −20 kb upstream region (highlighted by yellow) of hTERT TSS (Highlighted by green) that show enrichment of H3K27ac and H3K4me1 specifically in telomerase-positive embryonic stem cells (WA01) and cancer cells (PC-3), but not in telomerase-negative primary fibroblast cells (IMR90). The interaction between hTERT promoter and the −20 kb enhancer region can be observed from 4C data done in A375 and BLM cells. Cis-interactions with FDR < 0.05 were selected for visualization (arcs). The blue arcs represent the interaction of hTERT promoter with HoxC5 and Pbx4-binding region (FDR = 6.3E-137). The gray color arcs are other significant interactions with hTERT promoter. b ChIP was performed against RNA polymerase II (Pol2), H3K4me1, and H3K27ac in PC-3 cells overexpressing control GFP or Flag-tagged HOXC5 followed by qPCR with primers specific for hTERT TSS, −10 kb and −20 kb upstream enhancer regions as indicated. c ChIP was performed against RNA polymerase II (Pol2), H3K4me1, and H3K27ac in A375 cells overexpressing control GFP or Flag-tagged HOXC5 followed by qPCR with primers specific for hTERT TSS, −10 kb and −20 kb upstream enhancer regions as indicated. d ChIP was performed against RNA polymerase II (Pol2), H3K4me1, and H3K27ac in WA01 cells before (P0) and after neural differentiation (P4) followed by qPCR with primers specific for hTERT TSS, −10 kb and −20 kb upstream enhancer regions as indicated. e The expression of endogenous hTERT mRNA in A375 cells co-expressing dCas9-KRAB with control sgRNAs or sgRNAs targeting the HoxC5-binding region at −20 kb upstream hTERT enhancer. f, The top ten biological processes associated with endogenous HoxC5-binding sites in PC-3 cells. The p value is based on the Binomial or Hypergeometric test. The pathways involved in cell differentiation are highlighted in red. vp view point