Trans-activation of the human immunodeficiency virus long terminal repeat by the hepatitis B virus X protein

Human immunodeficiency virus 1 has been implicated as the main etiologic agent of the acquired immunodeficiency syndrome. However, other infectious agents may accelerate the progression of this disease. In particular, hepatitis B virus has been suggested as one such cofactor. Therefore, we have investigated the effects of hepatitis B virus gene products on expression of the human immunodeficiency virus I in transient transfection studies of Jurkat lymphoblastic T cells, using as reporter the chloramphenicol acetyltransferase gene coupled to the long terminal repeat of human immunodeficiency virus I. As measured by the amount of chloramphenicol acetyltransferase activity, gene expression directed by the human immunodeficiency virus I long terminal repeat increased approximately 10-fold in response to the hepatitis B virus X protein. This trans-activation by the X protein is multiplicative with the effect of phorbol esters and can be accounted for by an increase in the steady-state level of chloramphenicol acetyltransferase mRNA. Analysis of deletion and clustered point mutants in the long terminal repeat indicated that the X protein exerts its effect through multiple cis-acting sites. These results provide a possible molecular basis for the association of hepatitis B virus and the acquired immunodeficiency syndrome and confirm that the X protein is a transcriptional transactivator.