POSTTRANSCRIPTIONAL REGULATION ASSOCIATED WITH CONTROL OF HUMAN CD8A EXPRESSION OF CD4(-CELLS() T)

Lack of expression of a cell surface protein can occur by means of tra nscriptional and/or post-transcriptional mechanisms. Expression of the CD8A gene has been shown to be regulated by post-transcriptional mech anisms when 1) CD4-CD8(lo) thymocytes are blocked from differentiating into CD4(+)CD8(+) cells by TCR crosslinking and 2) upon activation of mature CD8(+) T cells. We demonstrate in this paper that there is als o post-transcriptional regulation of CD8A expression in a CD4(+)CD8(-) T-cell Line Jurkat. On the basis of northern blotting, mRNA for CD8A was not seen to be present in the Jurkat cells, but the gene was obser ved to be transcriptionally active in nuclear run-on analysis. In addi tion, we provide evidence that post-transcriptional mechanisms also co ntribute to the regulation of CD8A expression in mature CD4+CD8- T cel ls, challenging the assumption that the regulation is due solely to tr anscriptional mechanisms.