Neighbour and temperature effects on base-analogue-induced mutation in phage T4

The effect of neighbouring base pairs and of temperature on mutation frequencies were measured at nonsense sites in the T4 rII region. 2AP-induced AT→GC transition frequencies are insensitive to nearest-neighbour effects, while 5BU-induced ones are promoted by GC neighbours on the 5′ side. The effect of temperature on 2AP-and 5BU-induced mutation frequencies shows no simple dependence on nearest neighbours. These results are incompatible with a unitary mechanism as explanation for the effects of nearest neighbours and temperature on baseanalogue-induced mutagenesis.