Transcriptional regulation of HLA-DRA gene

Transcriptional regulation of class II genes is complex. DRA, for example, is expressed in both tissue-specific and lymphokine-inducible fashion. High levels of expression in B and activated T cells depend upon a lymphoid-specific transcriptional enhancer located in the first intron and on the upstream and downstream promoter elements. Conserved upstream promoter Z and X sequences (CUS) are the main determinants of this complex regulation. At least four distinct trans-acting factors that might be differentially expressed in various cell types bind to these Z and X boxes. These are members of JUN, helix-loop-helix (HLH), C/EBP and ETS families of proteins.