Developmental Regulation of the Murine CD4 Gene

CD4 is a membrane bound glycoprotein that plays an important role in T cell development and activation. An extensive analysis of the CD4 locus identified potential transcriptional control elements located 5\u27 of the promoter and within the first intron. Since the molecular mechanism for the control of CD4 expression during T cell development had not been determined, it is the focus of this dissertation. A series of recombinant DNA constructs were made to determine the contribution of putative transcriptional control elements in regard to CD4 expression, and to identify elements being used to control CD4 expression during T cell development. One of these control elements, located within the first intron, was further characterized to determine the DNA sequence involved. In addition, the 15 kb 5\u27 of the promoter and the 9 kb first intron were sequenced and analyzed for homology to previously identified control elements. Our results indicate that there are multiple cis-acting elements which control the expression of the murine CD4 gene. Elements that have a positive effect on the expression of the CD4 gene are located: (1) about 13.5 kb 5\u27 of the first exon; and (2) within the first intron. Elements that have a negative effect on the expression of the CD4 gene are located: (1) near the 5\u27 enhancer; (2) between the promoter and 5\u27 enhancer; (3) within the first intron about 2.5 kb 3\u27 of the promoter; and (4) within the first intron about 4 kb 3\u27 of the promoter. In addition, the enhancer located 13.5 kb 5\u27 of the promoter stimulates transcription from the CD4 promoter when the enhancer is left in it’s native context as long as some of the intervening DNA sequence is deleted. The negative element located within the first intron about 4 kb 3\u27 of the promoter corresponds to a GATA repeat. Sequence analysis of the DNA regions containing these positive and negative elements indicates regions of DNA that could be responsible for the functional activity associated with particular regions