Identification of putative reader proteins of 5-methylcytosine and its derivatives in Caenorhabditis elegans RNA

Methylation of carbon-5 of cytosines (m5C) is a post-transcriptional nucleotide modification of RNA with widespread distribution across organisms. m5C has been shown to participate in mRNA transport and maintain mRNA stability through its recognition by the reader proteins ALYREF and YBX1, respectively. We recently showed that m5C is required for Caenorhabditis elegans development and fertility under heat stress. To contribute to the understanding of how m5C and its oxidative derivatives mediate their functions, we developed RNA baits bearing modified cytosines in diverse structural contexts to pulldown potential readers in C. elegans . Our mass spectrometry analyses reveal unique binding proteins for each of the modifications. We validate our dataset by demonstrating that the nematode ALYREF homologues ALY-1 and ALY-2 preferentially bind m5C in vitro. The dataset presented here serves as an important scientific resource that will support the discovery of new functions of m5C and its derivatives. ### Competing Interest Statement E.A.M. is a co-founder and director of Storm Therapeutics, Cambridge, UK.