THE GENE-EXPRESSION OF HUMAN FOAMY VIRUS DOES NOT REQUIRE A POSTTRANSCRIPTIONAL TRANSACTIVATOR

Human foamy virus (HFV) comprises a complex genomic organization of ga g, pol, env, and several nonstructural genes such as bell, bel2, bel3, bet, beo, and bes located between env and 3' LTR. Among these viral n onstructural genes, bell appears to encode an essential transactivator of LTR-directed gene expression. To investigate the roles of the othe r nonstructural proteins for the viral replication, a series of provir al mutants were generated and tested for their in vitro replication. T he mutations in the other than bell open reading frame did not show an y significant effect on viral replication. The bell protein is the onl y essential transactivator for the LTR-directed transcription. To dete rmine whether HFV has an essential post-transcriptional transactivator like the rev protein of human immunodeficiency virus type 1, or the r ex protein of human T cell leukemia virus type 1, we investigated the bell-independent expression of the HFV gag structural gene under the c ontrol of the heterologous simian virus 40 promoter. We demonstrated t hat the expression of the HFV gag structural gene does not require an essential post-transcriptional transactivator. Thus, it appears that t he regulation of HFV gene expression is distinct from that of other hu man retroviruses. (C) 1994 Academic Press, Inc.