GATA1 Binding Kinetics on Conformation-Specific Binding Sites Elicit Differential Transcriptional Regulation.

GATA1 organizes erythroid and megakaryocytic differentiation by orchestrating the expression of multiple genes that show diversified expression profiles. Here, we demonstrate that GATA1 monovalently binds to a single GATA motif (Single-GATA) while a monomeric GATA1 and a homodimeric GATA1 bivalently bind to two GATA motifs in palindromic (Pal-GATA) and direct-repeat (Tandem-GATA) arrangements, respectively, and form higher stoichiometric complexes on respective elements. The amino-terminal zinc (N) finger of GATA1 critically contributes to high occupancy of GATA1 on Pal-GATA. GATA1 lacking the N finger-DNA association fails to trigger a rate of target gene expression comparable to that seen with the wild-type GATA1, especially when expressed at low level. This study revealed that Pal-GATA and Tandem-GATA generate transcriptional responses from GATA1 target genes distinct from the response of Single-GATA. Our results support the notion that the distinct alignments in binding motifs are part of a critical regulatory strategy that diversifies and modulates transcriptional regulation by GATA1.