Chipping away at GATA

GATA-1 is a hematopoietic lineage-specific transcription factor that is important for erythroid-specific gene expression patterns. In the March 5 Proceedings of the National Academy of Sciences, Christine Horak and colleagues at Yale University describe an approach to mapping transcription factor binding sites in mammalian genomes (Proc Natl Acad Sci USA 2002, 99:2924-2929). They looked at GATA-1 binding to the β-globin locus in human K562 erythroleukemia cells using chromatin immunoprecipitation (ChIP) combined with microarray analysis (ChIP-chip). They immunoprecipitated GATA-1 using three different antibodies and hybridized immunopurified genomic DNA to arrays containing fragments of the 75 kb β-globin locus. Two β-globin regions were consistently enriched, the HS2 core-element region known to bind GATA-1 and a region upstream of the gammaG gene. They then used PCR analysis to confirm and further define the GATA-binding region. These results demonstrate the feasibility of applying ChIP-chip methodology to comprehensive analysis of an entire mammalian locus.