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The DNA deaminase family encompasses enzymes that have been highly conserved throughout vertebrate evolution and which display wide-ranging positive effects upon innate and adaptive immune system and development. Activation-induced cytidine deaminase was identified as a DNA mutator after its necessity in the successful development of high-affinity B cells via somatic hypermutation, class switch recombination, and gene conversion was determined. APOBEC3 exhibits the ability to deaminate retroviral first strand cDNA in a variety of viral infections, including HIV and hepatitis. Recent work has highlighted the potential importance of activation-induced cytidine deaminase (AID) and APOBEC1 in epigenetic reprogramming, and also the role that AID and the APOBECs may have in the development of cancer. In addition to the known activities of these members of the protein family, there are still other deaminases, such as APOBEC2, whose targets and functions are as yet unknown. This chapter provides the details of two assays that have proved to be invaluable in elucidating the exact specificities of deaminases both in vitro and in Escherichia coli. The application of these assays to future studies of the deaminase family will provide an indispensible tool in determining the potentially diverse functions of the remainder of this family of enzymes.

Two types of colonies of laboratory mice were employed; hierarchically organized ones formed by placing five unfamiliar 8-week-old mice in a cage together and amicably organized colonies in which four male litter mates were kept together throughout the whole period of the experiment. During a 21-day pre-experimental period intra-colony aggressive behaviour was recorded. A dominant animal and ranked subordinates occurred in every hierarchical colony, whilst no aggression was recorded in any of the amicable colonies. During a 25-day period unfamiliar adult male or female mice were introduced daily into the amicable or hierarchical colonies for 10 min. In a third experiment juvenile mice 17, 24, 31 or 38 days old were introduced into hierarchically organized colonies during a 20-day period. In all hierarchical colonies the stranger was attacked irrespective of sex and age; the majority of attacks were carried out by the dominant mouse. Aggression by the dominant declined exponentially throughout the experimental period and regression analyses compared the different data. Unfamiliar adult females were the recipients of fewer attacks than unfamiliar adult males and the age of juvenile strangers was found to be an important factor. Amicably organized mice initially did not attack strangers, but over a period of 25 days the number of attacks on unfamiliar males gradually increased.