APOBEC3s: DNA-editing human cytidine deaminases.

Area of Science:

• Biochemistry and Molecular Biology
• Immunology
• Genetics

Background:

• Nucleic acid editing enzymes, including cytidine deaminases from the apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like (APOBEC) super family, are vital for the human immune system.
• These enzymes target viral pathogens and somatically mutate immunoglobulins, playing roles in both defense and adaptive immunity.
• DNA-editing APOBEC3 enzymes are gaining attention for their implications in cancer development and their potential utility in gene-editing technologies.

Purpose of the Study:

• To review and compare the structural characteristics, DNA binding interactions, substrate specificity, and activity of APOBEC3 (A3) domains.
• To highlight recent structural insights into DNA-editing APOBEC3 enzymes, specifically A3A and A3G, bound to single-stranded DNA (ssDNA).
• To identify remaining knowledge gaps concerning the biological functions and misregulation consequences of APOBEC3 enzymes.

Main Methods:

• Review of existing literature and crystal structures of APOBEC3 domains.
• Analysis of structural data to understand enzyme-DNA binding interfaces.
• Comparison of substrate specificity and activity profiles across different APOBEC3 enzymes.

Main Results:

• Recent crystal structures of A3A and A3G enzymes bound to ssDNA offer detailed views of substrate binding.
• These structures provide insights into the determinants of substrate specificity for these DNA-editing enzymes.
• Comparisons reveal variations in target sequence specificity and subcellular localization among APOBEC3 family members.

Conclusions:

• Structural data on A3A and A3G have advanced our understanding of DNA binding and specificity mechanisms.
• Significant unknowns persist regarding enzyme cooperativity, broader nucleic acid interactions, and systematic substrate preference quantification for many APOBEC3s.
• Further research is essential to fully characterize the biological functions of APOBEC3s and the consequences of their misregulation in health and disease.