Avian tumor virus proteins and RNA in uninfected chicken embryo cells.

The content of proteins P19 and P15 (mol wt 19,000 and 15,000, respectively) of avian leukovirus in various types of uninfected chicken embryos has been determined by radioimmunoassay. All chicken embryos examined, including embryos which have thus far been classified as group specific (gs) antigen negative by complement fixation tests, contained these viral proteins as well as P27 as previously reported. The embryos known as "gs antigen-positive" type contained about five times as much of these viral proteins as did the "gs antigen-negative" type. The ratio of the three viral proteins was similar for all types of embryos, suggesting that the genes for these proteins are coordinately controlled. In contrast to the relatively high levels of viral internal proteins in gs antigen-negative cells, the amounts of virus-specific RNA detectable by molecular hybridization were extremely low. The levels of helper activity, which presumably reflect the level of viral envelope glycoprotein, were also generally low or undetectable in these cells. Thus, the expression of the gene for envelope glycoprotein does not appear to be controlled coordinately with the genes for viral internal proteins.