The genome's best friend

DNA replication through mononucleotide runs is frequently associated with slippage of DNA polymerase, leading to the insertion or deletion of a small number of base pairs. A new study shows that, in the absence of DOG-1, a putative helicase, long poly(dG/C) runs are associated with deletions that extend into flanking DNA sequences. This mutational signature may be related to the ability of poly(dG) to form secondary structures such as G-quadruplex DNA, and may contribute to the genomic instability of tumor cells.