Characterization of ICPO, an immediate-early polypeptide of herpes simplex virus type II

It has been previously reported that herpes simplex virus poly peptides undergo cascade synthesis and are coordinately regulated, three kinetic classes of polypeptides described were the immediate—early class, which contains nonstructural polypeptides, the early class, which contains nonstructural and structural polypeptides, and the late class, which contains predominantly structural polypeptides.

The focus of these studies was to characterize an immediate-early using either a monospecific antiserum or pulse-labeling with radioisotopes. It (1) the antiserum directed against HSV-2 ICPO with only HSV-2 ICPO and not HSV-1 ICPO; (2) ICPO of HSV-2 remained The polypeptide, ICPO of HSV-2, directed against ICPO of HSV-2 was found that: reacted in the infected cell through 24 hrs postinfection and the use of the amino acid analogues azetidine and canavanine allowed an enhanced accumulation of ICPO within the infected cell; (3) ICPO was primarily found in the nuclear fraction of HSV-2 infected cells maintained in the presence or absence of azetidine, whereas in canavanine-treated cells ICPO primarily found in the cytoplasmic fraction and exhibited was a more heterogeneous apparent molecular weight; and (4) ICPO associated strongly with the nonsoluble component of nuclear preparations. The strong association of ICPO with the nuclear fraction and the nonsoluble component of the nuclear fraction suggest that ICPO may be associated with the chromatin or nuclear matrix of infected cells. The possibility of a regulatory role for ICPO with respect to viral gene expression and/or the establishment and maintenance of latency is discussed.