Translational regulator that ensures constant high levels of translation upon a variety of stress conditions, such as amino acid starvation, UV-C irradiation, proteasome inhibitor treatment and glucose deprivation. Plays a role as a negative regulator of the EIF2AK4/GCN2 kinase activity; impairs GCN1-mediated EIF2AK4/GCN2 activation, and hence EIF2AK4/GCN2-mediated eIF-2-alpha phosphorylation and subsequent down-regulation of protein synthesis. Plays a role in differentiation of neuronal cells by stimulating neurite outgrowth. Interacts with GCN1; prevents the interaction of GCN1 with EIF2AK4/GCN2 and inhibits EIF2AK4/GCN2 kinase activity. Interaction with RPL39; this interaction occurs in a GCN1-independent manner. Associates with ribosomes; this interaction occurs in a GCN1-independent manner. Associates with actin; this interaction occurs in a GCN1-independent manner. Belongs to the IMPACT family.