The enhancers in the genomic regions of KLF3 and KLF11 were excluded because they demonstrated enhancer activities in non-erythroid cells as well.
Unlike −31, this region does not demonstrate enhancer activity in reporter assays, but does have insulator enhancer-blocking activity.
CTRL2 has been shown to bind CTCF and demonstrated enhancer blocking activity in vitro [13], therefore it appears repeat sequences that can bind to CTCF may form a secondary structure which confers enhancer blocking activity.
Case-control studies have implicated rare HRAS minisatellite alleles in cancer risk [ 24, 25], and specific HRAS minisatellite alleles have demonstrated enhancer or suppressor activity in vitro [ 26].
Reporter assays demonstrated increased enhancer activity of the T allele compared with the C allele in beta cell lines [ 40].
By measuring the number of K562 colonies obtained for each of the constructs under selection with geneticin, we were able to demonstrate enhancer-blocking activity for all four of the test regions (Figure 4c), consistent with these regions having insulator activity.
In contrast, KLF3-I, KLF6-II, KLF6-III, and KLF13-III demonstrated strong enhancer activities with KLF3, KLF6 or KLF13 promoters, but not with minP, indicating that KLF3-I, KLF6-II, KLF6-III, and KLF13-III are gene-specific enhancers, and that their enhancer activities are independent of the TATA box [ 49] (Table 1).
Tbx5-dependent ncRNAs emanated from regions that are enriched for TBX5-binding and that demonstrated Tbx5-dependent enhancer activity.
Recently, Pekowska et al. [ 34] demonstrated that reduced enhancer activity is associated with the loss of H3K4me3 and concurrent increase in H3K4me1 in T cells.
Our analysis failed to demonstrate promoter and/or enhancer activity in the immediate 5'-flanking region of exon A1b, between exons A1b and 1, and in the 3'-UTR.
