The role of p202 in regulating hematopoietic cell proliferation and differentiation.

HIN-200 proteins are interferon (IFN)-inducible proteins that can regulate cell proliferation and differentiation in vitro. Characterization of the lineage and cell type-dependent expression of Ifi202 revealed little or no expression of Ifi202 in the Lin(-)/c-Kit+ fraction enriched for immature hematopoietic progenitor cells (HPCs) but higher levels in more differentiated Lin(-)/c-Kit(-) and Lin+ populations. The highest levels of Ifi202 expression were observed in CD11b+/Gr-1dim immature granulocytes in the bone marrow. In the peripheral blood, Ifi202 was expressed only in the myeloid lineage, with the highest level of expression seen in CD11b+/Gr-1dim immature granulocytes. Constitutive expression of p202 in primary HPCs delayed proliferation of these cells in vitro, caused a reduction in the number and size of myeloid colonies growing on methylcellulose, and affected the ability of the cells to reconstitute irradiated mice but did not significantly affect cell differentiation. Thus, p202 plays a role in regulating the proliferative capacity of hematopoietic cells.