Changes in GATA1 occupancy determine whether HEXIM1 promotes RNAPII recruitment or enforces RNAPII pausing. (A) Three-dimensional correlation plot between HEXIM1, GATA1, RNAPII occupancy, and chromatin accessibility. Each dot represents a gene; the red color gradient represents HEXIM1 occupancy; x-axis represents GATA1 occupancy, y-axis represents RNAPII occupancy, and z-axis represents chromatin accessibility. (B) Heat map showing gained GATA1 sites also gained RNAPII and HEXIM1 occupancy and chromatin accessibility in HEXIM1 OE cells. (C) Quantification of changes in GATA1, RNAPII, HEXIM1 occupancy, and chromatin accessibility at gained GATA1 sites. (D-F) GATA1, HEXIM1 occupancy, and PI at genes for which the PI increases more than twofold in the indicated cell lines. (G) GATA1 occupancy at downregulated genes in the indicated cell lines. (H) Profiles of GATA1 and RNAPII occupancy at paused genes. At paused genes there is loss of GATA1 (top). There is also increased ser5 RNAPII at the promoter and decreased ser5 RNAPII in the gene body (bottom), resulting in an increased PI. (I) Examples of enhanced RNAPII recruitment facilitated by increased GATA1 occupancy (left), and enhanced pausing facilitated by decreased GATA1 (right).