(D) Mutant alleles used in this study. CRISPR-Cas9 strategy for creation and screening of catalytically inactive alleles of nsun-1 (mj473), nsun-2 (mj458) and nsun-4 (mj457). A homologous recombination template bearing a point mutation to convert the catalytic cysteine into alanine whilst creating a restriction site for HaeIII was co-injected. For the study of nsun-5, a 928 bp deletion allele (tm3898) was used. Image not to scale. 