Putative transcription factor, weakly pro-apoptotic when overexpressed (By similarity). Tumor suppressor. Required for early embryonic stem cell development. Displaces isoform 4 at the onset of differentiation, required for repression of stemness genes. 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 nucleus after pro-apoptotic stimuli (By similarity). Translocates to the mitotic spindle upon loss of interaction with H3K4me3 during early mitosis. Ubiquitous. The PHD-type zinc finger forms an aromatic cage around H3K4me3. Defects in DIDO1 may be a cause of myeloid neoplasms.