Herpesvirus-associated nuclear antigen(s) in cells biochemically transformed by fragments of herpesvirus DNA and in somatic cell hybrids

Abstract

Human and mouse cells biochemically transformed by ultraviolet light (UV)-irradiated HSV-1 express HSV-1 thymidine kinase (TK) activity and also express type-specific herpesvirus-associated nuclear antigen(s) (HANA). To identify the HSV-1 DNA sequences coding for HANA and their location on the viral genome, studies were carried out on: (i) somatic cell hybrid clones obtained by fusing mouse [LM(TK −)] cells with UV-irradiated HSV-1-transformed human [HeLa(BU25)/KOS 8-1] cells; and (ii) LM(TK −) cells biochemically transformed with restriction endonuclease fragments of DNA which code for HSV-1 TK. Molecular hybridization experiments were also carried out and demonstrated that HSV-1 DNA sequences coding for TK were integrated in the biochemically transformed cells. The human-mouse somatic cell hybrid clones (LH81) which were HSV-1 TK+ were also HANA +, while clones counterselected in bromodeoxyuridine which had lost HSV-1 TK activity and DNA sequences likewise lost HANA. Previous studies had shown that the HSV-1 TK gene of LH81 hybrid clones was associated with a marker chromosome, designated M7, which consists of a human chromosome 17 translocated to the short arm of chromosome 3, or a modified M7 chromosome containing a translocation from a mouse chromosome. The present results indicate that at least one HANA gene was integrated in the same chromosome as the HSV-1 TK gene. LM(TK −) cells biochemically transformed by HSV-1 DNA restriction nuclease fragments of diminishing size, which map in the HpaI-I region (26.2 to 31.7) of the HSV-1 genome, were HANA + as well as TK +. The HANA + cells included LM(TK −)/TF pAGO PP and LM(TK −)/TF pAGO PS clones. The latter are clones of LM(TK −) cells biochemically transformed, respectively, by a PvuII fragment (1.35 × 10 6 daltons) and a PvuII- SmaI fragment (0.9 × 10 6 daltons; 30.2 to 31.1 map units) of HSV-1 DNA derived from Escherichia coli plasmid, pAGO. Since the PvuII- SmaI DNA fragment has only enough genetic information to code for a polypeptide of about 53,000 daltons and the HSV-1 TK polypeptide is about 40,000 daltons, the findings indicate that the genes for HSV-1 TK and one herpesvirus-associated nuclear antigen are either contiguous or overlapping, or HSV-1 TK and one HANA gene are identical.