The LDB1 complex co-opts CTCF for erythroid lineage specific long-range enhancer interactions

Lineage-specific transcription factors are critical for long-range enhancer interactions but direct or indirect contributions of architectural proteins such as CTCF to enhancer function remain less clear. The LDB1 complex mediates enhancer-gene interactions at the {beta}-globin locus through LDB1 self-interaction. We find that a novel LDB1-bound enhancer upstream of carbonic anhydrase 2 (Car2) activates its expression by interacting directly with CTCF at the gene promoter. Both LDB1 and CTCF are required for enhancer-Car2 looping and the domain of LDB1 contacted by CTCF is necessary to rescue Car2 transcription in LDB1 deficient cells. Genome wide studies and CRISPR/Cas9 genome editing indicate that LDB1-CTCF enhancer looping underlies activation of a substantial fraction of erythroid genes. Our results provide a mechanism by which long-range interactions of architectural protein CTCF can be tailored to achieve a tissue-restricted pattern of chromatin loops and gene expression.