Gene Regulation and Immunodeficiency 
tion were examined. Since effects of these ago- 
nists and Tat were synergistic, infection by DNA 
viruses might be an important cofactor in progres- 
sion from latent disease to clinical AIDS. 
Thus the quest to rescue the expression of class 
II major histocompatibility genes in a rare human 
congenital disease has led to genetic approaches 
to the study of transcription by RNA polymerase 
II and to the elucidation of a potent new tran- 
scriptional regulatory mechanism. 
326 
