Mitochondrial (mt) biogenesis depends on both the nuclear and mt genomes, and a coordination of these two genetic systems is necessary for proper cell functioning. Little is known about the regulatory mechanisms of mt translation or about the expression of mt translation factors. Here, we studied the expression of mt translation factors during TPA-induced terminal differentiation of HL-60 cells. For all mt translation factors investigated, mRNA expression was markedly downregulated in a coordinate and specific manner, while mRNA levels for the cytoplasmic translation factors showed only a slight reduction. An actinomycin D chase study and nuclear run-on assay revealed that the TPA-induced decrease in mt elongation factor Tu (EF-Tumt) mRNA, mainly results from decreased mRNA stability. Polysome analysis showed that there was no significant translational control of mt translation factor (EF-Tumt, ribosomal proteins L7/L12mt and S12mt) mRNA expression during differentiation. Thus, the decreased protein level of one of these mt translation factors (EF-Tumt) simply reflects its decreased mRNA level. It was also demonstrated by pulse-labeling of mt translation products, that the downregulation of mt translational activity is actually associated with downregulated mt translation factor expression during cellular differentiation. Our results illustrate that the regulatory mechanisms of mt translational activity upon terminal differentiation - in response to the growth arrest  is different to that of the cytoplasmic system, where the control of mRNA translational efficiency of major translation factors is the central mechanism for their downregulation.