LDB1-mediated enhancer looping independent of the RNA Pol II transcription initiation complex, Mediator and cohesin

Authors

• I Krivega
• A Dean

Abstract

The LDB1 complex regulates erythroid enhancers and mechanistic studies of the -globin locus indicate that LDB1 dimerization brings the beta-globin gene into proximity with the LCR for transcription activation. The role of co-activators in establishing this long range interaction is poorly understood. We eliminated the RNA Pol II pre-initiation complex from the beta-globin promoter by deleting the TATA-box and initiator using CRISPR/Cas9 editing. While transcription was lost, enhancer-promoter interaction was unaffected. Additional deletion of the promoter GATA1 site eliminated LDB1 complex and Mediator occupancy and resulted in loss of enhancer-promoter interaction. However, a mutant form of LDB1 was able to support LCR/beta-globin promoter interaction without Mediator core occupancy. Moreover, ENCODE data and ChIP showed that cohesin was almost completely absent from LDB1-regulated erythroid enhancer-gene pairs. We conclude that beta-globin enhancer-promoter looping depends on the LDB1 complex but is independent of the Pol II pre-initiation complex, Mediator and cohesin.

Scientific Focus Area: Molecular Biology and Biochemistry

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