Required for early embryonic stem cell development (By similarity). Putative transcription factor, weakly pro-apoptotic when overexpressed. Interacts specifically (via PHD-type zinc finger) with histone H3 that is trimethylated at 'Lys-4' (H3K4me3), histone phosphorylation at 'Thr-3' or 'Thr-6' disrupts this binding and promotes translocation of DIDO1 from chromatin to the mitotic spindle during mitosis. Translocates to the mitotic spindle upon loss of interaction with H3K4me3 during early mitosis (By similarity). Translocates to the nucleus after pro-apoptotic stimuli. Ubiquitous. Expressed at intermediate levels. Up-regulated during apoptosis. The PHD-type zinc finger forms an aromatic cage around H3K4me3.