Functions as part of the ATAC complex, a complex with histone acetyltransferase activity on histones H3 and H4 (PubMed:19103755). Inhibits the MAP3K12 activity to induce the activation of the JNK/SAPK pathway (PubMed:10801814). Together with MOCS2B, inhibits the activity of stress kinase EIF2AK2/PKR; this may lead to effects such as suppression of JNK activation and subsequent stress-responsive transcription, or suppression of eIF2a phosphorylation to favor translation (PubMed:26705305). {ECO:0000269|PubMed:10801814, ECO:0000269|PubMed:19103755, ECO:0000269|PubMed:26705305}. This is the function of MBIP (MAP3K12 binding inhibitory protein 1, Ensembl gene identifier ENSG00000151332).