Distinct mechanisms control RNA polymerase II recruitment to a tissue-specific locus control region and a downstream promoter

Histone acetylation precedes activation of many genes. However, the establishment and consequences of long-range acetylation patterns are poorly understood. To define molecular determinants of the developmentally dynamic histone acetylation pattern of the beta -globin locus, we compared acetylation of the locus in MEL and CB3 erythroleukemia cells. CB3 cells lack the beta -globin locus control region (LCR) binding protein p45/ NF-E2. We found that p45/NF-E2 was required for histone hyperacetylation at adult beta -globin promoters similar to 50 kilobases downstream of the LCR, but not at the LCR. Surprisingly, RNA polymerase II associated with the LCR in a p45/NF-E2-independent manner, while its recruitment to the promoter required p45/NF-E2. We propose that polymerase accesses the LCR and p45/ NF-E2 induces long-range transfer of polymerase to the promoter, resulting in transcriptional activation.