GATA-1-Mediated Proliferation Arrest during Erythroid Maturation

Abstract

Transcription factor GATA-1 is essential for erythroid and megakaryocytic maturation. GATA-1 mutations are associated with hematopoietic precursor proliferation and leukemogenesis, suggesting a role in cell cycle control. While numerous GATA-1 target genes specifying mature hematopoietic phenotypes have been identified, how GATA-1 regulates proliferation remains unknown. We used a complementation assay based on synchronous inducible rescue of GATA-1⁻ erythroblasts to show that GATA-1 promotes both erythroid maturation and G₁ cell cycle arrest. Molecular studies combined with microarray transcriptome analysis revealed an extensive GATA-1-regulated program of cell cycle control in which numerous growth inhibitors were upregulated and mitogenic genes were repressed. GATA-1 inhibited expression of cyclin-dependent kinase (Cdk) 6 and cyclin D2 and induced the Cdk inhibitors p18 ^INK4C and p27 ^Kip1 with associated inactivation of all G₁ Cdks. These effects were dependent on GATA-1-mediated repression of the c-myc (Myc) proto-oncogene. GATA-1 inhibited Myc expression within 3 h, and chromatin immunoprecipitation studies indicated that GATA-1 occupies the Myc promoter in vivo, suggesting a direct mechanism for gene repression. Surprisingly, enforced expression of Myc prevented GATA-1-induced cell cycle arrest but had minimal effects on erythroid maturation. Our results illustrate how GATA-1, a lineage-determining transcription factor, coordinates proliferation arrest with cellular maturation through distinct, interrelated genetic programs.

ACKNOWLEDGMENTS

M.B.R. and J.J.W. contributed equally to this work.

This work was funded by the Johnson and Johnson Focused Giving Award and the American Society of Hematology Junior Faculty Award (M.J.W.). J.J.W. was funded by NIH Pediatric Hematology Research Training Program grant HL07150.

We thank Elizabeth Keiper and Katherine Dugan for technical assistance in the microarray studies. We thank Chuck Sherr for reagents and advice.