Homologies between class I and II promoters.

(A) The upstream regions of DRA,2 HLA-B57,28and HLA-A127 are aligned to illustrate similarities in sequence and structure. The DRA S, X1, X2, X3, and Y boxes2,13,14 and the class I ENH-A and ENH-B regions and previously identified Rel, R, IRE, R1, X1, α, and inverted CAAT (IC) box control elements are indicated.15,18,24 32-34 Asterisks indicate the residues of HLA-A loci that disrupt the consensus sequences of the IRE, R1, and α sites. (B) Lower-case letters indicate base changes introduced into the HLA-B57 sequence for mutant EMSA probes and HLA-B CAT reporters.