No abstract

Expression of two monkey metallothioneins in yeast leads to complementation of both known functions of the endogenous yeast copperthionein gene, namely copper detoxification and autoregulation of transcription. The metallothionein-like proteins of higher and lower eukaryotes are therefore functionally analogous despite their dissimilar primary sequences.

The gibbon lymphosarcoma cells releasing gibbon ape leukemia virus were used in a screening study of sera from healthy humans. Out of 72 sera screened by indirect immunoelectronmicroscopy using this system, 55 were positive (76%); i.e., 26 out of 35 males (74%) and 29 out of 37 females (78%). The highest incidence of antibody production was in 1-to 1O-year-olds and 31-to 40-year-olds, with the adults exhibiting higher levels. Differences in incidence of natural antibody were not found to be sex-linked. These findings suggest that type C RNA viruses related to the gibbon ape leukemia virus and simian (woolly monkey) sarcoma virus family as well as the baboon endogenous type C virus family may be widespread in humans.

A variety of transplantable mouse tumor lines were shown to contain murine type C viruses and virus-associated antigens. The type of virus isolated and antigens detected could not invariably be correlated with the original method of tumor induction, but testing of the majority of tumor lines for infectious virus at various levels of in vivo or in vitro passage yielded isolates that were consistent in tissue culture host range for each tumor. In contrast, during the course of in vivo transplantation, some of the lines underwent considerable change in the pattern of virus-associated cell-surface antigens. When the transplanted tumor lines were placed into culture, all showed some alteration in the detectable surface antigens. Upon retransplantation and passage of the cultured cells in mice, the surface antigens gradually returned to the original in vivo patterns and occasionally acquired additional type C virus-associated antigens not detected in the original tumor line. To test for association of antigens with infectious virus, appropriate tissue culture cell lines were infected with the viruses isolated from the tumors. In these infected indicator cells, some new virus-associated cell-surface and virion evelope antigens were detected, but the complete array of antigens found in the original tumor lines was not acquired. These findings indicated the presence of several different type C viruses in long transplanted cell lines and demonstrated that environmental and host cell factors may have major influences on expression of virus-associated antigens.