Fig. 1. Identification of candidate core enhancer regions. (A) Restriction endonuclease accessibility assays identify three regions of accessible chromatin [+17, +18 and +19; numbering corresponds to distances in kb from the start of exon 1a in two haematopoietic progenitor cell lines (EML-C1, 416B)]. (B) Diagram of the murine SCL locus indicating the three regions of open chromatin above a homology profile of a human/mouse sequence alignment. All sites for AvaII, HaeIII and HinfI are indicated. The summary shows the three regions accessible to endonucleases (black boxes labelled +17, +18 and +19) which correspond to peaks within the homology profile.