CDK1 kinase assays using histone H1 as a substrate demonstrated that at both early (24 h pi) and late (32 h pi) time points following MVM infection, CDK1 activity was reduced, to levels seen following control doxorubicin treatment which blocks cells in G2 (Figure 4, panels a and i, compare lanes 1 and 2 with lane 3). The gene discussed is H1-0; the disease is infection.