O-glycosylation at Thr-440 in the SET domain by OGT is essential for the histone methyltransferase and the coactivator activity toward RARA in granulopoiesis (By similarity). The absence of Thr-440 glycosylation in assays done in vitro may explain why PubMed:18952892 and PubMed:19264965 did not detected any histone methyltransferase activity for this protein.