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In lytic infection with simian virus 40 and polyoma virus of monkey and mouse cells in tissue culture, synthesis of the viral tumor (T) antigens (T antigens) is rapidly followed by a mitogenic response of the host cell. The latter begins with virus-induced stimulation of overall cellular RNA and protein synthesis, leading to a substantial increase in cytoplasmic and nuclear RNA and protein. Stimulation begins within 1 hr after onset of T-antigen synthesis and also occurs if virus-induced DNA synthesis is blocked by metabolic inhibitors. The broad spectrum of biological and molecular effects induced by simian virus 40 and polyoma virus is, at least phenotypically, reminiscent of the pleiotropic impact exerted on target cells by nonviral mitogens and by certain growth-promoting steroid and polypeptide hormones.Simian virus 40 (SV40) and polyoma virus induce a lytic infection in permissive cells and an abortive ("transforming") infection in nonpermissive cells. These infections exhibit considerable similarity (for details and references, see ref. 1). Expression of the early viral gene-i.e., synthesis of virus-specific early 19S mRNAs and of the tumor antigens (T antigens), is rapidly followed by a mitogenic reaction of the host cell. This reaction includes virus-induced stimulation of overall cellular RNA synthesis and an increase in total, mainly ribosomal RNA, activation of the cellular DNA-synthesizing apparatus and duplication of the host cell chromatin (S phase). In nonpermissive cells, virus-induced S phase is followed by prophase and mitosis but no viral DNA is replicated. In permissive cells, S phase is paralleled by replication of viral DNA as a nucleohistone and by production of progeny virus and is followed by cell death (lysis). The early events of infection, including the activation of the cellular DNA-synthesizing apparatus, also occur if virus-induced DNA synthesis is blocked by metabolic in-In this paper we report that, in lytic infection, SV40-and polyoma-induced stimulation of cellular RNA synthesis is paralleled by stimulation of cellular protein synthesis which also occurs in the presence of araC or FdUrd.MATERIALS AND METHODS Primary mouse kidney (2), secondary monkey kidney, and CV-1 (a monkey kidney cell line) cultures were grown in 10-cm-diameter plastic dishes in reinforced Eagle's medium ("culture medium") containing 10% fetal bovine serum (GIBCO) (3,4 To separate cells into cytoplasmic and nuclear fractions, cultures were incubated for 10 min at 40C in lysis buffer (300 mM sucrose/10 mM Tris-HCI, pH 7.4/5 mM NaCI/3 mM MgCl2/0.5% Nonidet P-40), 1 ml per dish. The cells were scraped from the plates and passed through a syringe (20-gauge needle) seven times, and the lysate was centrifuged at 3000 X g for 15 min at 40C.To extract proteins, unfractionated cultures were suspended, at 1.0 ml per dish, in 1% NaDodSO4/1 mM NaH2PO4, pH 8.5; nuclear pellets were suspended in 0.25 ml per dish. To cytoplasmic fractions (1 ml per dish) 50 ,ul of 20% (wt/vol) NaDodSO4 was added. The lysates were...

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