Retinoblastoma gene inhibits transactivation of HIV-LTR linked gene expression upon co-transfection in He La cells.

Co-transfection of HeLa cells with plasmids carrying human immunodeficiency virus (HIV) control elements along with plasmids harboring human retinoblastoma (RB) gene, results in the repression of transactivation of genes linked to HIV elements. Cells transfected with HIV LTR-linked chloramphenicol acetyl transferase (CAT) and TAT genes showed a dose-dependent decrease in CAT activity when increasing amounts of RB genes were transfected along with HIV genes. CAT mRNAs were not detected in HeLa cells transfected with HIV LTR CAT gene alone. Upon cotransfection of these cells with pTAT gene, large quantities of CAT messengers were observed. The TAT gene mediated expression of CAT gene was inhibited when cells were co-transfected with RB gene. These studies suggest that the RB gene represses HIV LTR directed CAT gene expression by interfering with the expression of HIV TAT gene.