[Vertebrate immunity: mutator proteins and their evolution]

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Genetics

Background:

• Error-prone DNA repair mechanisms contribute to cellular mutations.
• Y-family DNA polymerases and Activation-Induced Deaminase (AID) are key players in mutagenesis.
• AID/APOBEC deaminases are involved in immune system gene diversification.

Purpose of the Study:

• To identify and characterize new members of the AID/APOBEC family.
• To explore the evolutionary origins and functions of cytidine deaminases.
• To understand the role of these enzymes in generating genetic diversity.

Main Methods:

• Bioinformatic analysis to identify novel AID/APOBEC family members.
• Sequence analysis and comparison of identified enzymes.
• Literature review of known mutagenesis and immune gene diversification mechanisms.

Main Results:

• A new AID/APOBEC family member, APOBEC5, was identified in the bacterium *Xanthomonas oryzae*.
• The widespread distribution of RNA/DNA editing deaminases suggests an ancient origin.
• These enzymes play critical roles in both evolution and ontogeny, particularly in immune responses.

Conclusions:

• APOBEC5 represents a novel bacterial cytidine deaminase within the ancient AID/APOBEC family.
• The findings underscore the ancient and conserved role of cytidine deaminases in generating genetic diversity across diverse organisms.
• This discovery expands our understanding of the evolutionary landscape of DNA/RNA editing enzymes.