Controlling Hematopoiesis through Sumoylation-Dependent Regulation of a GATA Factor.

Abstract 1467

Poster Board I-490

GATA factors function via distinct modes to establish transcriptional networks that control fundamental developmental processes including hematopoiesis. Whereas the master regulator of hematopoiesis GATA-1 is subject to multiple posttranslational modifications, how these modifications influence GATA-1 activity at endogenous loci is poorly understood. GATA-1 is sumoylated at K137, which resides in the N-terminus, but how the N-terminus contributes to GATA-1 function remains unclear. Expression of a GATA-1 mutant lacking amino acids 1-83 of the N-terminus is linked to the development of acute megakaryoblastic leukemia [Wechsler et al. (2002) Nat. Genet. 32, 148], and deletion of the N-terminus preferentially deregulates a subset of target genes [Johnson et al. (2006) PNAS. 103, 15939]. We demonstrate that sumoylation at K137 promotes transcriptional activation only at a subset of its target genes – those requiring the cell type-specific coregulator, Friend of GATA-1 (FOG-1). Interestingly, a GATA-1 mutation that disrupts FOG-1 binding (V205G) and K137 mutations yielded similar phenotypes, although FOG-1 was not required for K137 sumoylation. Both V205 and K137 mutations dysregulated GATA-1 chromatin occupancy at select sites, FOG-1-dependent target gene expression, and were rescued by tethering SUMO-1. While FOG-1- and SUMO-1-dependent genes migrated away from the nuclear periphery upon erythroid maturation, FOG-1- and SUMO-1-independent genes localized at the periphery independent of maturation. These results illustrate how sumoylation of a critical developmental regulator selectively controls its function at specific loci, and members of a target gene ensemble with distinct coregulator and posttranslational modification requirements reside in different subnuclear compartments.