Multiple interactions between regulatory regions are required to stabilize an active chromatin hub

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Abstract
The human β-globin locus control region (LCR) is required for the maintenance of an open chromatin configuration of the locus. It interacts with the genes and the hypersensitive regions flanking the locus to form an active chromatin hub (ACH) transcribing the genes. Proper developmental control of globin genes is largely determined by gene proximal regulatory sequences. Here, we provide the first functional evidence of the role of the most active sites of the LCR and the promoter of the β-globin gene in the maintenance of the ACH. When the human β-globin gene promoter is deleted in the context of a full LCR, the ACH is maintained with the β-globin gene remaining in proximity. Additional deletion of hypersensitive site HS3 or HS2 of the LCR shows that HS3, but not HS2, in combination with the β-globin promoter is crucial for the maintenance of the ACH at the definitive stage. We conclude that multiple interactions between the LCR and the β-globin gene are required to maintain the appropriate spatial configuration in vivo.