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HMG-I binds to GATA motifs: implications for an HPFH syndrome.
We have examined binding of the nuclear protein HMG-I to the human gamma-globin promoter. We find that HMG-I binds preferentially to the more 3' of a pair of GATA motifs in the gamma-globin promoter; this paired motif is bound by the erythroid factor GATA-1. A naturally occurring mutation (-175 T-C) in the area bound by HMG-I results in overexpression of gamma-globin in adult red blood cells (HPFH) and up-regulation of the gamma-globin promoter in in vitro expression assays; HMG-I does not bind to this mutant sequence. A survey of GATA motifs from other globin cis-elements demonstrates HMG-I binding to most of them. These findings implicate HMG-I in the HPFH phenotype; we speculate that it may participate in the formation of multiprotein complexes that regulate globin gene expression.
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