INVIVO FUNCTION OF REGULATORY DNA-SEQUENCE ELEMENTS OF A MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-I GENE

Major histocompatibility complex class I genes are expressed in nearly all somatic tissues, although their level of expression varies. By analysis of a set of promoter deletion mutants introduced into transgenic mice, a complex regulatory element, consisting of overlapping enhancer and silencer activities, is demonstrated to function as a tissue-specific regulator of class I expression. The enhancer activity predominates in lymphoid tissues but not in nonlymphoid tissues. In contrast to the tissue-specific function of the complex regulatory element, a second novel silencer element is shown to function in both lymphoid and nonlymphoid tissues. The complement of DNA-binding factors in different cell lines is shown to correlate with the levels of class I expression.