Controlling long-range genomic interactions at a native locus by targeted tethering of a looping factor.
Chromatin loops juxtapose distal enhancers with active promoters, but their molecular architecture and relationship with transcription remain unclear. In erythroid cells, the locus control region (LCR) and β-globin promoter form a chromatin loop that requires transcription factor GATA1 and the associated molecule Ldb1. We employed artificial zinc fingers (ZF) to tether Ldb1 to the β-globin promoter in GATA1 null erythroblasts, in which the β-globin locus is relaxed and inactive. Remarkably, targeting Ldb1 or only its self-association domain to the β-globin promoter substantially activated β-globin transcription in the absence of GATA1. Promoter-tethered Ldb1 interacted with endogenous Ldb1 complexes at the LCR to form a chromatin loop, causing recruitment and phosphorylation of RNA polymerase II. ZF-Ldb1 proteins were inactive at alleles lacking the LCR, demonstrating that their activities depend on long-range interactions. Our findings establish Ldb1 as a critical effector of GATA1-mediated loop formation and indicate that chromatin looping causally underlies gene regulation.
Division of Hematology, The Children's Hospital of Philadelphia, PA 19104, USA.
Wulan
W
Deng
Jongjoo
J
Lee
Hongxin
H
Wang
Jeff
J
Miller
Andreas
A
Reik
Philip D
PD
Gregory
Ann
A
Dean
Gerd A
GA
Blobel
D000818:Animals; D002460:Cell Line; D002469:Cell Separation; D002843:Chromatin / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000166:cytology; D004900:Erythroblasts / Q000378:metabolism; D005260:Female; D050982:GATA1 Transcription Factor / Q000378:metabolism; D005786:Gene Expression Regulation; D060588:LIM Domain Proteins / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D051379:Mice; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D014158:Transcription, Genetic; D016335:Zinc Fingers; D055544:beta-Globins / Q000235:genetics*
D002843:Chromatin; D004268:DNA-Binding Proteins; D050982:GATA1 Transcription Factor; C494689:Gata1 protein, mouse; D060588:LIM Domain Proteins; C102084:Ldb1 protein, mouse; D055544:beta-Globins