Variations in viral gene expression in friend virus-transformed cell lines congenic with respect to the H-2 locus

The effect of H-2 genotype on the genetic expression of Friend oncovirus was studied using Friend virus-transformed cells differing genetically only at the H-2 locus. Seven lines and three sublines were examined with regard to expression of Friend virus and the murine leukemia virus envelope glycoprotein gp69/71, the structural proteins p30 and p15 (FMR), and reverse transcriptase. Our results confirm that H-2^b, H-2^g and H-2^kh cell lines were stable upon serial passage for production of infectious Friend virus, whereas the H-2^d and H-2^k cell lines ceased to release infectious virus after a relatively short time. Synthesis of viral proteins by these cell lines was independent of the synthesis of infectious virus in that some viral proteins continued to be synthesized by H-2^d and H-2^k cell lines in the absence of infectious virus. Reduction of viral proteins can be attributed to the loss of expression of individual viral genes. The temporal sequence of change suggests that the loss of protein expression may occur in a stepwise fashion; reverse transcriptase was reduced first, followed by p30 and p15, and gp69/71 last. The results confirm that p30 and p15 are coordinately expressed. In contrast, the expression of p30 and gp69/71 are noncoordinate, indicating that these proteins are regulated by independent genetic loci. Loss of viral genes did not occur, since cell lines which had previously ceased to synthesize viral proteins could be chemically induced to produce infectious NB tropic Friend viruses. These data suggest that for these H-2-congenic cell lines, there is an association of the H-2D^b allele and the long-term production and release in vitro of both infectious virus and viral proteins.