The function of XRN1 (5'-3' exoribonuclease 1, Ensembl gene identifier ENSG00000114127) is as follows. Major 5'-3' exoribonuclease involved in mRNA decay (PubMed:18172165, PubMed:33472058). Required for the 5'-3'-processing of the G4 tetraplex-containing DNA and RNA substrates (By similarity). The kinetic of hydrolysis is faster for G4 RNA tetraplex than for G4 DNA tetraplex and monomeric RNA tetraplex (By similarity). Plays a role in replication-dependent histone mRNA degradation (PubMed:18172165). May act as a tumor suppressor protein in osteogenic sarcoma (OGS) (PubMed:12426100). {ECO:0000250|UniProtKB:P97789, ECO:0000269|PubMed:12426100, ECO:0000269|PubMed:18172165, ECO:0000269|PubMed:33472058}.