Expression of immediate-early genes in herpes simplex virus type 1-infected XC cells: lack of ICP22 (68K) polypeptide.

The expression of immediate-early (IE) genes of herpes simplex virus type 1 (HSV-1, MP strain) in non-permissive rat XC cells was analysed and compared with the expression of IE genes in permissive HEp-2 cells by the following three methods: analysis of virus polypeptide synthesis in infected cells, Northern blot hybridization between poly(A) nuclear or cytoplasmic RNA and in vitro labelled virus DNA or plasmid-cloned fragments corresponding to IE genes, and ability of poly(A) cytoplasmic RNAs to direct synthesis of virus polypeptides in vitro. ICP4 (175K), ICP0 (110K) and ICP27 (62K) were synthesized in XC cells although in smaller amounts than in HEp-2 cells; ICP4 is functional since early and late polypeptides could be observed. Their corresponding mRNAs were present at low levels in nuclei and in cytoplasm and are functional since the polypeptides were synthesized in a rabbit reticulocyte system. ICP22 (68K) was not detectable in infected XC cells; its mRNA was present in nuclei and in cytoplasm, but it is not functional since the corresponding polypeptide was not synthesized in a rabbit reticulocyte system. This suggests some structural differences in the ICP22 mRNA molecules in infected XC and HEp-2 cells and implicates cellular determinants in the control of the expression of HSV-1 IE genes.