GATA-1 binding to the αV promoter negatively regulates expression of the integrin αV subunit in human leukemic K562 cells.

Recently we observed that the transcription factors Sp1 and Sp3 bind to the CTCCTCCTC sequence located between positions -194 and -172 of the αV promoter region and are directly involved in the regulation of transcriptional activity of the αV gene in human umbilical vascular endothelial cells (HUVECs) (Czyz & Cierniewski, 1999, Eur. J. Biochem. 265, 638). In this report we provide evidence that the GATA-1 factor regulates αV expression during differentiation of pluripotent K562 cells induced either by phorbol 12-myristate 13-acetate (PMA) or butyric acid (BA) through interaction with the GATA element in the αV gene promoter. DNase I footprinting analysis revealed that region -413 to -408, covering the GATA binding site, was protected by nuclear extract from K562 cells. There was no protection of this region by HUVEC nuclear extract. Electrophoretic mobility shift assay (EMSA) analysis of nuclear extract of K562 cells treated with BA revealed an increase in GATA binding activity, which was associated with reduced αV mRNA and αV protein on the cell surface. Stimulation of K562 cells with PMA resulted in opposite effects: lower expression of GATA-1 was associated with increased levels of αV. We conclude that the GATA-1 transcription factor specifically binds to the GATA element in the αV gene promoter and negatively regulates αV gene expression.