CELL-LINES CONTAINING AND EXPRESSING THE HUMAN HERPESVIRUS 6A TS GENEARE PROTECTED FROM BOTH H-RAS AND BPV-1 TRANSFORMATION

Human herpesvirus 6A (HHV-6A) strain U1102 was previously shown to con tain a 1473 bp transformation suppressor gene (ts) (Araujo et al,, 199 5), Ts inhibited transformation of NIH3T3 cells by H-vas and transcrip tion of the H-uas and human immunodeficiency type 1 (HIV-1) promoters in transient transfection experiments. In the current study, stable NI H3T3 cell lines expressing ts protein were established by transfection with pRc-ts containing the ts gene under the control of the Rous sarc oma virus (RSV) long terminal repeat (LTR) and a neomycin selectable m arker. Selected cell lines contained approximately one to two copies p er cell of intact ts sequences, expressed ts protein and grew at appro ximately the same rate as parental NIH3T3 cells. These cell lines were protected from H-ras transformation while parental and NIH3T3 cells c ontaining the ts gene cloned in the antisense orientation were not. Ex pression of the chloramphenicol acetyl transferase (CAT) gene under th e control of the EJ-H-ras promoter was also suppressed in the ts cell lines but not when the CAT gene was under the control of the murine os teosarcoma virus LTR or human cytomegalovirus immediate early promoter . When NIH3T3 cell lines expressing ts protein were established by inf ection with the retrovirus, LNCts, the cells expressed ts protein and were protected from H-ras transformation, Furthermore, bovine papillom avirus type 1 (BPV-1) transformation was also suppressed in cells cotr ansfected with BPV-1 plus ts and in ts expressing cell lines transfect ed with BPV-1. The BPV-1 p89 and p2443 promoters were down-regulated i n 3T3-ts lines. Because the human papillomavirus type 16 (HPV-16) p97 promoter has similarity to the BPV-1 p89 promoter, the ability of ts t o suppress p97 was also tested. Like the H-ras and BPV-1 promoters, HP V-16 p97 was downregulated in 3T3-ts lines. The data indicate the util ity of ts against H-ras, BPV-1 and HPV-16 promoters and their respecti ve oncogenes.