FUNCTIONAL-CHARACTERIZATION OF A CHICKEN MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-II B-GENE PROMOTER

A 0.7 kilobase (kb) DNA fragment from the 5' flanking region of a chic ken major histocompatibility complex (MHC) class II B gene was cloned into chloramphenicol acetyltransferase (CAT) reporter vectors and was transfected into a chicken macrophage cell line that expresses a low l evel of MHC class II antigens. Positive orientation-dependent promoter activity of the chicken DNA was evident in a reporter construct conta ining an SV40 enhancer. Deletion analysis of this 0.7 kb DNA fragment revealed a short fragment in the 3' end that was crucial for the promo ter function and negative regulatory elements (NRE) located further up stream. The conserved MHC class II X and Y boxes did not have a signif icant effect on promoter activity. Sequence analysis of the 0.7 kb cla ss II B gene upstream region suggests possible involvement of interfer on (IFN), E twenty-six specific (ETS)-related proteins, and other fact ors in regulating this promoter. A chicken T-cell line culture superna tant increased surface expression of MHC class II antigens, as well as class II promoter activity, in this macrophage cell line. This first functional characterization of a chicken MHC class II B gene promoter will aid in understanding the regulatory mechanisms that control the e xpression of these genes.