MafK/NF-E2 p18 is required for beta-globin genes activation by mediating the proximity of LCR and active beta-globin genes in MEL cell line

Evidences indicate that locus control region (LCR) of beta-globin spatially closes to the downstream active gene promoter to mediate the transcriptional activation by looping. DNA binding proteins may play an important role in the looping formation. NF-E2 is one of the key transcription factors in beta-globin gene transcriptional activation. To shed light on whether NF-E2 is involved in this process, DS19MafKsiRNA cell pools were established by specifically knocked down the expression of MafK/NF-E2 p18, one subunit of NF-E2 heterodimer. In the above cell pools, it was observed that the occupancy efficiency of NF-E2 on beta-globin gene locus and the expression level of beta-globin genes were decreased. H3 acetylation, H3-K4 methylation and the deposition of RNA polymerase 11, but not the recruitment of GATA-1, were also found reduced at the beta-globin gene cluster. Chromosome Conformation Capture (3C) assay showed that the cross-linking frequency between the main NF-E2 binding site HS2 and downstream structural genes was reduced compared to the normal cell. This result demonstrated that MafK/NF-E2 p 18 recruitment was involved in the physical proximity of LCR and active beta-globin genes upon beta-globin gene transcriptional activation. (C) 2008 Published by Elsevier Ltd.