Required for RNA-mediated gene silencing (RNAi). Binds to short RNAs such as microRNAs (miRNAs) or short interfering RNAs (siRNAs), and represses the translation of mRNAs which are complementary to them. Lacks endonuclease activity and does not appear to cleave target mRNAs. May also be required for transcriptional gene silencing (TGS) of promoter regions which are complementary to bound short antigene RNAs (agRNAs). Interacts with DDB1, DDX5, DDX6, DHX30, DHX36, DDX47, DICER1, AGO2, ELAVL1, HNRNPF, IGF2BP1, ILF3, IMP8, MATR3, MOV10, PABPC1, PRMT5, RBM4, SART3, TNRC6B, UPF1 and YBX1. Associates with polysomes and messenger ribonucleoproteins (mNRPs) (By similarity). Interacts with LIMD1, WTIP and AJUBA (By similarity). Interacts with APOBEC3F, APOBEC3G and APOBEC3H (By similarity). Ubiquitinated on surface-exposed lysines by a SCF-like E3 ubiquitin-protein ligase complex containing ZSWIM8 during target-directed microRNA degradation (TDMD), a process that mediates degradation of microRNAs (miRNAs). Ubiquitination by the SCF-like E3 ubiquitin-protein ligase complex containing ZSWIM8 leads to its subsequent degradation, thereby exposing miRNAs for degradation. ZSWIM8 recognizes and binds AGO1 when it is engaged with a TDMD target. Belongs to the argonaute family. Ago subfamily.