ABC-me: a novel mitochondrial transporter induced by GATA-1 during erythroid differentiation

Transcription factor GATA-1 is essential for normal erythropoiesis. GATA-bi nding sites are consistently found in promoters or enhancers of genes expre ssed selectively in erythroid cells, To discover novel GATA-1-regulated gen es, we searched for GATA-1-activated transcripts in G1E cells, an erythroid line derived from GATA-1(-) embryonic stem cells. By subtractive analysis, we identified a new ATP-binding cassette (ABC) transporter that is strongl y and rapidly induced by GATA-1. This protein, named ABC-me (for <(ABC)unde r bar>-(m) under bar itochondrial (e) under bar rythroid), localizes to the mitochondrial inner membrane and is expressed at particularly high levels in erythroid tissues of embryos and adults. ABC-me is induced during erythr oid maturation in cell lines and primary hematopoietic cells, and its overe xpression enhances hemoglobin synthesis in erythroleukemia cells. The ABC p roteins participate in diverse physiological processes by coupling ATP hydr olysis to the transport of a variety of substrates across cell membranes. W e speculate that ABC-me, a newly identified erythroid-expressed ABC superfa mily member, may mediate critical mitochondrial transport functions related to heme biosynthesis.