GABP controls a critical transcription regulatory module that is essential for maintenance and differentiation of hematopoietic stem/progenitor cells

Maintaining a steady pool of self-renewing hematopoietic stem cells (HSCs) is critical for sustained production of multiple blood lineages. Many transcription factors and molecules involved in chromatin and epigenetic modifications have been found to be critical for HSC self-renewal and differentiation; however, their interplay is less understood. The transcription factorGAbinding protein (GABP), consisting of DNA-binding subunit GABP alpha and transactivating subunit GABP beta, is essential for lymphopoiesis as shown in our previous studies. Here we demonstrate cell-intrinsic, absolute dependence on GABP alpha for maintenance and differentiation of hematopoietic stem/progenitor cells. Through genome-wide mapping of GABP alpha binding and transcriptomic analysis of GABP alpha-deficient HSCs, we identified Zfx and Etv6 transcription factors and prosurvival Bcl-2 family members including Bcl-2, Bcl-X(L), and Mcl-1 as direct GABP target genes, underlying its pivotal role in HSC survival. GABP also directly regulates Foxo3 and Pten and hence sustains HSC quiescence. Furthermore, GABP activates transcription of DNA methyltransferases and histone acetylases including p300, contributing to regulation of HSC self-renewal and differentiation. These systematic analyses revealed a GABP-controlled gene regulatory module that programs multiple aspects of HSC biology. Our studies thus constitute a critical first step in decoding how transcription factors are orchestrated to regulate maintenance and multipotency of HSCs. (Blood. 2011; 117(7):2166-2178)