Directs the termination of nascent peptide synthesis (translation) in response to the termination codons UAA, UAG and UGA (By similarity). Component of the transient SURF complex which recruits UPF1 to stalled ribosomes in the context of nonsense-mediated decay (NMD) of mRNAs containing premature stop codons (By similarity). Required for SHFL-mediated translation termination which inhibits programmed ribosomal frameshifting (-1PRF) of mRNA from viruses and cellular genes. Heterodimer of two subunits, one of which binds GTP (By similarity). Component of the transient SURF (SMG1-UPF1-eRF1-eRF3) complex (By similarity). Belongs to the eukaryotic release factor 1 family.