Disease mutations provide unique opportunities to decipher protein and cell function. Mutations in the master regulator of hematopoiesis GATA-2 underlie an immunodeficiency associated with myelodysplastic syndrome and leukemia. We discovered that a GATA-2 disease mutant (T354M) defective in chromatin binding was hyperphosphorylated by p38 mitogen-activated protein kinase. p38 also induced multisite phosphorylation of wild-type GATA-2, which required a single phosphorylated residue (S192). Phosphorylation of GATA-2, but not T354M, stimulated target gene expression. While crosstalk between oncogenic Ras and GATA-2 has been implicated as an important axis in cancer biology, its mechanistic underpinnings are unclear. Oncogenic Ras enhanced S192-dependent GATA-2 phosphorylation, nuclear foci localization, and transcriptional activation. These studies define a mechanism that controls a key regulator of hematopoiesis and a dual mode of impairing GATA-2-dependent genetic networks: mutational disruption of chromatin occupancy yielding insufficient GATA-2, and oncogenic Ras-mediated amplification of GATA-2 activity.
This study shows that p38α increases GATA-2 activity at endogenous target genes by inducing GATA-2 multi-site phosphorylation. Oncogenic Ras is found to amplify this mechanism, which provides a potential molecular explanation for the cooperative promotion of cancer development by Ras and GATA-2.
- p38α promotes multi-site GATA-2 phosphorylation, increasing its localization in nuclear foci enriched in an active form of RNA polymerase II and its capacity to regulate endogenous target genes.
- A single serine residue within GATA-2, Ser192, mediates p38α-dependent multisite phosphorylation and enhanced GATA-2 activity.
- Oncogenic Ras amplifies p38α- and Ser192-dependent GATA-2 multi-site phosphorylation and function, thus providing a framework for understanding Ras–GATA-2 interactions in the development and progression of cancer.