Translesion DNA synthesis-driven mutagenesis in very early embryogenesis of fast cleaving embryos

• Published in: Nucleic acids research 2022-01, Vol.50 (2), p.885-898
• Main Authors: Lo Furno, Elena, Busseau, Isabelle, Aze, Antoine, Lorenzi, Claudio, Saghira, Cima, Danzi, Matt C, Zuchner, Stephan, Maiorano, Domenico
• Format: Article
• Language: English
• Subjects: Animals; DNA - metabolism; DNA Repair; Drosophila melanogaster - genetics; Drosophila melanogaster - growth & development; Drosophila melanogaster - metabolism; Genome Integrity, Repair and; Heterochromatin; Life Sciences; Mutagenesis; Mutation Rate; Xenopus laevis - genetics; Xenopus laevis - growth & development; Xenopus laevis - metabolism
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/gkab1223

Abstract In early embryogenesis of fast cleaving embryos, DNA synthesis is short and surveillance mechanisms preserving genome integrity are inefficient, implying the possible generation of mutations. We have analyzed mutagenesis in Xenopus laevis and Drosophila melanogaster early embryos. We report the occurrence of a high mutation rate in Xenopus and show that it is dependent upon the translesion DNA synthesis (TLS) master regulator Rad18. Unexpectedly, we observed a homology-directed repair contribution of Rad18 in reducing the mutation load. Genetic invalidation of TLS in the pre-blastoderm Drosophila embryo resulted in reduction of both the hatching rate and single-nucleotide variations on pericentromeric heterochromatin in adult flies. Altogether, these findings indicate that during very early Xenopus and Drosophila embryos TLS strongly contributes to the high mutation rate. This may constitute a previously unforeseen source of genetic diversity contributing to the polymorphisms of each individual with implications for genome evolution and species adaptation. Graphical Abstract Graphical Abstract Speculative model of early Xenopus embryo replisome. High Rad18 abundance induces both constitutive PCNA monoubiquitination (PCNAmUb) and active translesion DNA synthesis (TLS) generating mutations (red triangles) at high rate (+ sign). Both Rad18 homology-directed repair activity (HDR) and the mismatch repair system (MMR) function synergistically with TLS to reduce the mutation load (− sign). The Rad18 residues important for TLS activity (C28) and HDR activity (C207) are also indicated.