Promotes megakaryocyte differentiation by up-regulating RUNX1 expression (PubMed:25134913). Regulates RUNX1 expression by activating the proximal promoter of the RUNX1 gene and by enhancing the translation activity of an internal ribosome entry site (IRES) element in the RUNX1 gene (PubMed:25134913). Down-regulated in primary acute myeloid leukemia (AML) patients. Up-regulated in K562 and HEL cells undergoing megakaryocyte differentiation induced by phorbol myristate acetate (PMA). Belongs to the PITHD1 family.