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). Heterodimer of two subunits, one of which binds GTP (By similarity). Component of the transient SURF (SMG1-UPF1-eRF1-eRF3) complex (By similarity). Interacts with JMJD4 (By similarity). The ETF1-GSPT1 complex interacts with JMJD4 (By similarity). Hydroxylation at Lys-63 by JMJD4 promotes its translational termination efficiency. Methylated at Gln-185 by N6AMT1. Belongs to the eukaryotic release factor 1 family.