Ribosome collision sensor that plays a key role in the RNF14- RNF25 translation quality control pathway, a pathway that takes place when a ribosome has stalled during translation, and which promotes ubiquitination and degradation of translation factors on stalled ribosomes (PubMed:32610081, PubMed:36638793, PubMed:37651229, PubMed:37951215, PubMed:37951216). Directly binds to the ribosome and acts as a sentinel for colliding ribosomes: activated following ribosome stalling and promotes recruitment of RNF14, which directly ubiquitinates EEF1A1/eEF1A, leading to its degradation (PubMed:36638793, PubMed:37951215, PubMed:37951216). In addition to EEF1A1/eEF1A, the RNF14-RNF25 translation quality control pathway mediates degradation of ETF1/eRF1 and ubiquitination of ribosomal protein (PubMed:36638793, PubMed:37651229). GCN1 also acts as a positive activator of the integrated stress response (ISR) by mediating activation of EIF2AK4/GCN2 in response to amino acid starvation (By similarity). Interaction with EIF2AK4/GCN2 on translating ribosomes stimulates EIF2AK4/GCN2 kinase activity, leading to phosphorylation of eukaryotic translation initiation factor 2 (eIF-2-alpha/EIF2S1) (By similarity). EIF2S1/eIF-2-alpha phosphorylation converts EIF2S1/eIF-2- alpha into a global protein synthesis inhibitor, leading to a global attenuation of cap-dependent translation, and thus to a reduced overall utilization of amino acids, while concomitantly initiating the preferential translation of ISR-specific mRNAs, such as the transcriptional activator ATF4, and hence allowing ATF4-mediated reprogramming of amino acid biosynthetic gene expression to alleviate nutrient depletion (By similarity). {ECO:0000250|UniProtKB:E9PVA8, ECO:0000269|PubMed:32610081, ECO:0000269|PubMed:36638793, ECO:0000269|PubMed:37651229, ECO:0000269|PubMed:37951215, ECO:0000269|PubMed:37951216}. This is the function of ENSG00000089154 (GCN1, GCN1 activator of EIF2AK4).