SDS–PAGE/immunoblotting analysis of mouse cells expressing the human exon 1 La mRNAs after infection with herpes simplex type 1. Total extracts of mouse cells were analysed. Untransfected mouse 3T3 cells (3T3, lanes a, c, f, i); cell lines expressing the exon 1 La mRNA under control of the cytomegalovirus (CMV) promoter (lanes b, d, e, g, h, j, k). The cells were infected with the herpes simplex virus type 1 strain ANG ((+), lanes c, e, f, h, i, k) or not infected ((–), lanes d, g, j). Cells were analysed 1 h (lanes c, d, e), 4 h (lanes f, g, h) or 8 h (lanes i, j, k) p.i. M, Marker, lane 1 = 97.4 kD, 2 = 66 kD, 3 = 43 kD, 4 = 31 kD, 5 = 21.5 kD, 6 = 14.5 kD.