Involvement of RbAp48 in erythroid differentiation of murine erythroleukemia cells induced by sodium butyrate.

ABSTRACT

Normal mammalian terminal erythroid differentiation is a precisely regulated process during which the progenitor cells execute particular programs to form a mature erythrocytic phenotype. In the present study, it was found that RbAp48, a histone-binding protein associated with retinoblastoma protein, was upregulated during terminal erythroid maturation in vivo and in vitro. This indicated that RbAp48, at least in part, participated in the regulation of murine erythropoiesis. Following sodium butyrate (SB) induction, murine erythroleukemia (MEL) cells began to re-enter erythroid differentiation and the ratio of differentiated cells reached ~80% at 72 h. The erythroid maturation-related mRNA expression of α-globin, ß-globin and glycophorin A (GPA) was increased markedly, which indicated that SB induced MEL differentiation. During MEL differentiation, the RbAp48 level showed a 1.5-fold increase at 72 h, and the globin transcription factor (GATA)-1 level was also upregulated in the early stage of differentiation. By contrast, the c-Myc level was gradually downregulated in MEL differentiation. Using an immunofluorescence assay, the results of the study directly showed that the average fluorescence intensity of RbAp48 in each cell reached an almost 1.7-fold increase at 72 and 96 h. This was consistent with the western blot results of RbAp48 during MEL differentiation. In addition, reduced expression of RbAp48 by RNA inference decreased SB-induced MEL differentiation by ~20%, indicating that a high level of RbAp48 was essential for MEL differentiation. Taken together, these results established a functional link between RbAp48 and erythroid differentiation.