The 5' → 3' exoribonuclease XRN1/Pacman and its functions in cellular processes and development.

XRN1 is a 5' → 3' processive exoribonuclease that degrades mRNAs after they have been decapped. It is highly conserved in all eukaryotes, including homologs in Drosophila melanogaster (Pacman), Caenorhabditis elegans (XRN1), and Saccharomyces cerevisiae (Xrn1p). As well as being a key enzyme in RNA turnover, XRN1 is involved in nonsense-mediated mRNA decay and degradation of mRNAs after they have been targeted by small interfering RNAs or microRNAs.