Base-excision repair pathway shapes 5-methylcytosine deamination signatures in pan-cancer genomes

Transition of cytosine to thymine in CpG dinucleotides is the most frequent type of mutation in cancer. This increased mutability is commonly attributed to spontaneous deamination of 5-methylcytosine (5mC), which is normally repaired by the base-excision repair (BER) pathway. However, the contribution of 5mC deamination in the increasing diversity of cancer mutational signatures remains poorly explored. Here, we integrate mutational signatures analysis in a large series of tumor whole genomes with lineage-specific epigenomic data to draw a detailed view on 5mC deamination in cancer. We uncover tumor type-specific patterns of 5mC deamination signatures in CpG and non-CpG contexts. We demonstrate that the BER glycosylase MBD4 preferentially binds to open chromatin domains, which correlates with lower mutational burden in these domains. We validate our findings by modelling BER deficiencies in isogenic cell models. Overall, we establish MBD4 as the main actor responsible for 5mC deamination repair in humans.

Type: Cancer Genomics
Archiver: European Genome-Phenome Archive (EGA)

5 Datasets

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Dataset ID	Description	Technology	Samples
EGAD50000000763	Total RNA sequencing on 9 uveal melanomas. Libraries were prepared using the TruSeq Stranded Total RNA Library Prep Gold (Illumina, 20020599). Paired-end libraries (2 x 100 bp) were sequenced on a NovaSeq 6000 instrument (Illumina).	Illumina NovaSeq 6000	9
EGAD50000000764	Whole genome sequencing on 1 uveal melanoma and corresponding germline sample. Libraries were prepared using the Kapa HyperPrep kit (Roche, 07962363001). Paired-end libraries (2 x 150 bp) were sequenced on a NovaSeq 6000 instrument (Illumina).	Illumina NovaSeq 6000	2
EGAD50000000765	Whole genome sequencing on HAP-1 clones wild-type or knockout for MBD4 and/or TDG. Libraries were prepared using the Kapa HyperPrep kit (Roche, 07962363001). Paired-end libraries (2 x 100 bp) were sequenced on a NovaSeq 6000 instrument (Illumina).	Illumina NovaSeq 6000	20
EGAD50000000766	Whole Genome Bisulfite Sequencing on normal primary human uveal melanocytes. WGBS libraries were prepared using the Accel-NGS Methyl-Seq DNA Library Kit (Swift Biosciences 30024), the EZ DNA Methylation-Gold Kit (Zymo D5005), and DNA Clean & Concentrator-5 (Zymo D4013), following the instruction manual Accel-NGS Methyl-Seq DNA Library (Revision 160510). Paired-end (2 x 150 bp) libraries were sequenced on a DNBSEQ-T7 instrument (MGI) after library conversion.	DNBSEQ-T7	1
EGAD50000000767	Whole exome sequencing on 11 uveal melanoma samples and corresponding germline samples. Libraries were prepared using the SureSelectXT2 Clinical Research Exome V2 kit (Agilent, 5190-9500 and G9621B). Paired-end libraries (2 x 100 bp) were sequenced on HiSeq 2000/2500 or NovaSeq 6000 instruments (Illumina).	Illumina HiSeq 2000 Illumina HiSeq 2500 Illumina NovaSeq 6000	21