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Migrating bubble synthesis promotes mutagenesis through lesions in its template
Journal article   Open access   Peer reviewed

Migrating bubble synthesis promotes mutagenesis through lesions in its template

Beth Osia, Jerzy Twarowski, Tyler Jackson, Kirill Lobachev, Liping Liu and Anna Malkova
Nucleic acids research, Vol.50(12), pp.6870-6889
06/24/2022
DOI: 10.1093/nar/gkac520
url
https://doi.org/10.1093/nar/gkac520View
Published (Version of record) Open Access

Abstract

Break-induced replication (BIR) proceeds via a migrating D-loop for hundreds of kilobases and is highly mutagenic. Previous studies identified long single-stranded (ss) nascent DNA that accumulates during leading strand synthesis to be a target for DNA damage and a primary source of BIR-induced mutagenesis. Here, we describe a new important source of mutagenic ssDNA formed during BIR: the ssDNA template for leading strand BIR synthesis formed during D-loop migration. Specifically, we demonstrate that this D-loop bottom template strand (D-BTS) is susceptible to APOBEC3A (A3A)-induced DNA lesions leading to mutations associated with BIR. Also, we demonstrate that BIR-associated ssDNA promotes an additional type of genetic instability: replication slippage between microhomologies stimulated by inverted DNA repeats. Based on our results we propose that these events are stimulated by both known sources of ssDNA formed during BIR, nascent DNA formed by leading strand synthesis, and the D-BTS that we describe here. Together we report a new source of mutagenesis during BIR that may also be shared by other homologous recombination pathways driven by D-loop repair synthesis.

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