A3H-catalysed mutation in Vif-deficient HIV occurs most frequently within TCG and TCA motifs and least frequently within TCC and TCT motifs, and this result becomes even clearer on examination of weighted mutation frequencies (Supplementary Fig. 4) and more closely resembles the weighted mutation frequencies of the breast tumour data sets (Supplementary Fig. 3). The gene discussed is APOBEC3H; the disease is breast neoplasm.