STAT5A/B binding sites in a putative Tfr1 enhancer. (A) Putative STAT5A/B binding (GAS) sites within intron 1 of the Tfr1 gene (underlined). Three conserved GAS sites were identified with GAS 1 having the highest interspecies conservation. Sites are shown aligned with sequences from other species (www.ensembl.org/index.html). (B) Chromatin immunoprecipitation analysis of binding of active STAT5A to the putative GAS sites within intron 1 of Tfr1. See the complete figure in the article beginning on page 2071.