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Initiation of DNA replication at the human β-globin 3′ enhancer

The origin of DNA replication in the human β-globin gene contains an initiation region (IR) and two flanking auxiliary elements. Two replicator modules are located within the upstream auxiliary sequence and the IR core, but the functional sequences in the downstream auxiliary element are unknown. He...

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Bibliographic Details
Published in:Nucleic acids research 2005-01, Vol.33 (14), p.4412-4424
Main Authors: Buzina, Alla, Aladjem, Mirit I., Kolman, John L., Wahl, Geoffrey M., Ellis, James
Format: Article
Language:English
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Summary:The origin of DNA replication in the human β-globin gene contains an initiation region (IR) and two flanking auxiliary elements. Two replicator modules are located within the upstream auxiliary sequence and the IR core, but the functional sequences in the downstream auxiliary element are unknown. Here, we use a combination of benzoylated-naphthoylated DEAE (BND) cellulose purification and nascent strand abundance assays to show that replication initiation occurs at the β-globin 3′ enhancer on human chromosome 11 in the Hu11 hybrid murine erythroleukemia (MEL) cell line. To examine replicator function, 3′ enhancer fragments were inserted into an ectopic site in MEL cells via an optimized FRT/EGFP-FLP integration system. These experiments demonstrate that the 1.6 kb downstream auxiliary element is a third replicator module called bGRep-E in erythroid cells. The minimal 260 bp 3′ enhancer is required but not sufficient to initiate efficient replication, suggesting cooperation with adjacent sequences. The minimal 3′ enhancer also cooperates with elements in an expressing HS3β/γ-globin construct to initiate replication. These data indicate that the β-globin replicator has multiple initiation sites in three closely spaced replicator modules. We conclude that a mammalian enhancer can cooperate with adjacent sequences to create an efficient replicator module.
ISSN:0305-1048
1362-4962
DOI:10.1093/nar/gki747