Mikhail Gelfand and Marat Kazanov from Skoltech co-authored a preprint “APOBEC mutagenesis is low in most types of non-B DNA structures, unlike other types of cancer mutagenesis” that has been recently published in bioRxiv. The study focuse on the role of APOBEC enzymes in mutagenesis in non-canonical DNA structures during cancerogenesis. The researchers have demonstrated that in human cancers, the APOBEC mutagenesis is not enriched in direct repeats, mirror repeats, short tandem repeats, and G-quadruplexes. In contrast, they observed that the APOBEC-induced mutational density is positively associated with APOBEC activity in inverted repeats. The authors have also shown that, surprisingly, the APOBEC-signature mutation density per TC motif in the single-stranded DNA of a G-quadruplex (G4) is lower than in the four-stranded part of G4 and in B-DNA. Furthermore, the APOBEC mutagenesis, as well as the UV-mutagenesis in melanoma samples are absent in Z-DNA regions, due to depletion of their mutational signature motifs. Full text of the preprint is available here.