Cloning and characterization of a novel zinc finger protein (MDZF) that isassociated with monocytic differentiation of acute promyelocytic leukemia cells

Aim: To study the characteristics of a novel zinc finger protein designated as monocytic differentiation-associated zinc finger protein (MDZF) and its role in the differentiation of leukemia cells. Methods: The mRNA expressio n of MDZF in tissues and cells was analyzed by Northern blot and RT-PCR. Po lyclonal antibodies against the N terminus of MDZF were used to analyze pro tein expression in hematopoietic cell lines and subcellular location of MDZ F in promyelocytic NB4 cells. The NB4 cells treated with TPA or ATRA at dif ferent intervals were harvested and then the expression level of MDZF prote in was determined by Western blot. Result: A full-length cDNA was successfu lly identified from a human monocyte-derived dendritic cell cDNA library wh ich encodes 610 amino acids with eight C2H2 zinc finger motifs and one POZ domain. It was located on chromosome 3 according to the genome database. Th is novel zinc finger protein was designated as MDZF. One transcript isoform of MDZF was also cloned by RT-PCR. Northern blot showed that MDZF mRNA was restrictedly expressed in heart, skeleton muscle, kidney, liver, and place nta. MDZF protein was expressed in all hematopoietic cell lines examined. I mmunoblotting and confocal analysis indicated a dominant cytoplasmic locati on of MDZF in NB4 cells. Furthermore, after NB4 cells were treated with TPA for 48 h and differentiated into monocytes, MDZF expression increased five fold in the NB4 cells, but no effect was observed in NB4 cells treated with ATRA. Conclusion: A novel zinc finger protein MDZF was cloned. MDZF is upr egulated in monocytic, but not granulocytic, differentiation of NB4 acute p romyelocytic leukemia cells. MDZF may be a candidate regulator of monocytic differentiation.