Some characteristics of an early protein (ICP 22) synthesized in cells infected with herpes simplex virus.

In Vero cells incubated at 40 degrees C or treated with azetidine at 37 degrees C, synthesis of a polypeptide ('C') of apparent mol. wt. 66000 was stimulated. It was not phosphorylated and was found in the cytoplasmic fraction of cell lysates. In cells infected with herpes simplex virus type 1 (HSV-1) in the presence of azetidine, synthesis of cellular proteins, including polypeptide C, was suppressed and infected cell polypeptides ICP 4, 0, 22 and 27 (apparent mol. wt. 170000, 120000, 75000 and 60000, respectively) were made. All were phosphorylated and accumulated in the nucleus. Messenger RNA for the same four polypeptides was made in cells infected in the presence of cycloheximide. Thus, ICP 22 is distinct from cellular polypeptide C and is probably a virus-specific alpha polypeptide, although it differs from alpha ICP 4, 0 and 27 in that its rate of synthesis does not decline rapidly when later polypeptides are produced. It is modified after synthesis in at least two steps, the second of which may require a later virus-specific polypeptide. In cells infected with HSV-2 the synthesis of a polypeptide analogous to ICP 22 could not be detected.