Core integrated stress response (ISR) factor; optimizes ribosome collision-mediated Gcn2 activation and the downstream Gcn4-mediated transcriptional response; required for optimal stress-induced eIF2α (Sui2p) phosphorylation and downstream de-repression of GCN4 translation; Mbf1p is recruited to collided disomes and trisomes during the ISR; suppressor of frameshift mutations; protein abundance increases in response to DNA replication stress; homologous to human EDF1