Evolution is thought to proceed through the gradual accumulation of independent mutations in each new generation. In a study published online today in Genome Research, researchers analyzing hominid genomes have discovered thousands of clustered mutations likely resulting from the coordinated activity of APOBEC enzymes, leading to accelerated changes in DNA. Mutations occur through a variety of mechanisms, including mutagenic agents such as ultraviolet radiation, and error-prone cellular processes such as DNA replication and repair. In cancer, it was recently recognized that mutations could occur as the result of human APOBEC enzymes, which deaminate cytosines and lead to many clustered base substitutions in DNA. Interestingly, the APOBEC family, and in particular APOBEC3, have dramatically expanded in copy number in primates. The expansion is thought to be in response to the emergence of primate-specific viruses, which APOBECs target for inactivation. “Our results are at odds with assumptions of mutational models that are at the basis of most genetic analyses, including in medical genetics, evolutionary genetics, and population genetics,” co-corresponding author Keinan said. “It is tempting to suggest that some of the features that make us human are the result of this evolution ‘fast track’ option,” said co-corresponding author Levanon.
The study was funded by the European Research Council, the I-CORE Program of the Planning and Budgeting Committee in Israel, and the US National Institutes of Health.