Interacts with RB1 and EP300 and acts as a repressor of MYOD1 transactivation. Inhibits EP300 and CBP histone acetyltransferase activity. May be involved in coupling cell cycle exit to the transcriptional activation of genes required for cellular differentiation. May act as a candidate coinhibitory factor for NR0B2 that can be directly linked to transcription inhibitory mechanisms. Interacts via its LXCXE motif with the entire pocket region of RB1. Interacts with EP300, NR0B2 and TRIM27. May shuttle between nucleus and cytoplasm. Expressed in all adult tissues examined and during embryogenesis. Inhibition of MYOD1 may be partly due to the ability of EID1 to bind and inhibit EP300 histone acetyltransferase activity.