Intracellular localization of viral polypeptides during simian virus 40 infection.

African green monkey kidney cells infected by simian virus 40 were analyzed by immunofluorescence techniques for the nature and the time course of the appearance of viral polypeptides during infection. Reagents used in the study were anti-Vpl sera and affinity-purified anti-Vpl immunoglobulin G, anti-Vp3 sera, antivirus (anti-V) sera, and anti-tumor antigen sera. The results are summarized as follows. (i) Three types of staining, nuclear, perinuclear, and perinuclear accompanied by cytoplasmic staining, were observed in infected cells in reaction with anti-vpl antibody. In addition, a highly structured staining was observed at the periphery of nuclei of infected cells late in infection. (ii) In reaction with anti-Vp3 serum, the staining was confined within nuclei of cells throughout infection. (iii) Vp1 and Vp3 antigens seem to occupy different spacial regions of the nuclear area in cells. (iv) Vp1 and Vp3 antigens were expressed simultaneously during infection. (v) Centriolar staining observed early in infection paralleled the appearance of tumor (T-) antigen until 24 h after infection, after which time the frequency of positive centriolar staining decreased as infection progressed. (vi) T-antigen was first expressed at about 8 h after infection, and Vp1 and Vp3 antigens were first expressed at about 20 h after infection.

Vp1 affects intracellular localization of Vp3 polypeptide during simian virus 40 infection.

In order to understand the functions of simian virus 40 genes, permissive cells (TC7) were infected with mutants temperature sensitive in the complementation groups A, B, C, BC, and D at permissive and nonpermissive temperatures. Cells were examined for the localization of viral polypeptide antigens by immunofluorescent staining with monospecific antibodies. The results are as follows: (i) The appearance of Vp1 antigen in cells infected by tsB, C, or BC mutants was not affected appreciably by the mutations. (ii) The appearance of Vp3 antigen was affected by the mutations in B, C, or BC. Vp3 antigen is confined to the nuclei in cells infected by wild-type virus. With mutant virus infection, Vp3 antigen is found in the cytoplasm, perinuclear region, and nucleoli. (iii) The tsD mutants and the tsA mutants did not express either Vp1 or Vp3 antigens at the nonpermissive temperature. (iv) Nucleoli seem to play an essential role in the biosynthesis and assembly of viral polypeptides. Thus, mutations in any one of complementation groups B, C, or BC, which are within the structural gene for Vp1, cause an alteration of intracellular distribution of another late gene product, Vp3. These results suggest that the amino acid sequences of Vp1 polypeptide play a role(s) in the transport of viral antigens across internal membranes or in virus assembly processes or in both.