Possesses 5'->3' exoribonuclease activity (PubMed:11106401). Acts as an endogenous post-transcriptional gene silencing (PTGS) suppressor. Degrades miRNA-derived loops, excised during miRNA maturation in the nucleus (PubMed:17993620). Involved in pre-rRNA processing. Involved in the primary exonucleolytic shortening of the 5' external transcribed spacer (5'ETS), required for endonucleolytic processing at site P by the U3 snoRNP complex. Involved with XRN3 in the 5'-end processing of 5.8S and 25S rRNAs. Contributes with XRN3 to polyadenylation-dependent nuclear RNA surveillance. Involved in the degradation of aberrant polyadenylated pre-rRNA through 5'-end processing (PubMed:20338880). A number of isoforms are produced. According to EST sequences. Expressed in roots, leaves, stems and flowers. Belongs to the 5'-3' exonuclease family. XRN2/RAT1 subfamily. Truncated C-terminus. Was originally thought to correspond to two different genes At5g42540 and At5g42550. Was originally thought to correspond to two different genes At5g42540 and At5g42550. Truncated N-terminus.