XRN-1

XRN-1 is a highly efficient exoribonuclease that strictly requires a 5' monophosphate (5'-p) substrate. In the presence of Mg²⁺, it specifically digests 5'-monophosphorylated single-stranded RNA in the 5'→3' direction. XRN-1 also acts on 5'-monophosphorylated single-stranded DNA (ssDNA), albeit with significantly lower efficiency.

XRN-1 exhibits strict substrate specificity and cannot digest the following substrates: RNA bearing 5' triphosphate (5'‑ppp), 5' diphosphate (5'-pp), 5' cap (5'-cap), or 5' hydroxyl (5'-OH) termini; double-stranded DNA (dsDNA); and ssDNA with 5'-OH, 5'-ppp, or 5'-pp ends. In addition, it does not cleave double-stranded RNA with recessed 5'-phosphorylated termini, DNA/RNA hybrids, or 5'-phosphorylated RNA sequestered within stable secondary structures.

This enzyme is commonly used in sequencing library construction for the separation and enrichment of mRNA from total RNA, the removal of template DNA and by-products from in vitro transcription products, and the analysis of the 5' end of RNA for research purposes.