Further characterization of the murine cytomegalovirus induced early proteins in permissive and nonpermissive cells.

Abstract

Some of the properties of the immediate-early (IE) and early proteins induced by the murine cytomegalovirus (Smith strain) were examined in permissively infected 3 T 3-L 1 cells, and in non-permissively infected J 774A.1 (mouse macrophage) and human fibroblast cells, in order to determine differences that could account for the restriction in virus replication in the latter two cell lines. The different virus induced proteins had distinctive partitioning characteristics between nuclear and cytoplasmic fractions. The 96 K major IE protein had an exclusively nuclear association, as did the most abundant early proteins of 39 K and 36 K. The other viral proteins however were evenly distributed between nucleus and cytoplasm. In general these patterns were also seen in the infected non-permissive cells. Several proteins showed more than one charge isomer on two-dimension gels, and in addition five IE proteins and two early proteins were phosphorylated. Only two differences between the permissive and nonpermissive infections were observed; the IE proteins of 100 K and 89 K when synthesized in the human cells had a stronger affinity for the nuclear fraction; also a phosphorylated form of the 30 K IE protein was not detected in MCMV infected J 774 A.1 cells.