Phytohemagglutinin activation of the transcription of the bovine leukemia virus genome requires de novo protein synthesis.

Addition of supramitogenic doses of phytohemagglutinin (PHA) to short-term cultures of neoplastic or nonneoplastic lymphocytes infected with bovine leukemia virus increased the synthesis of the major core virion antigen (p25) by 5- to 10-fold. Such stimulation was not due to the mitogenic effect of PHA or to a generalized increase in cellular RNA or protein synthesis but rather to enhanced transcription of the viral genome by a PHA-induced protein.