Conserved major histocompatibility complex class II boxes--X and Y--are transcriptional control elements and specifically bind nuclear proteins.

Abstract

A conserved sequence motif exists at the 5'' end of all major histocompatibility complex class II genes. This motif consists of the 14-base X and Y boxes separated by a short stretch of variable sequence. In this report, we provide evidence that the X and Y boxes play an important role in controlling transcription of the murine class II gene E.alpha.k. We have developed transgenic mouse lines that carry E.alpha. genes cleanly deleted for either the X or Y box and have compared the expression of these mutant transgenes with that of a nondeleted control. Both the X and the Y segments appear critical for accurate and efficient transcription of E.alpha.k. The most drastic effect is seen with .gamma.-interferon-treated macrophages, where deletion of the Y box completely abrogates transcription initiated by the normal promoter. In addition, we identify proteins from nuclear extracts that bind specifically to the X or Y box.