TRANSCRIPTIONAL AND POSTTRANSCRIPTIONAL REGULATION OF ERYTHROID GENE-EXPRESSION IN ANTHRACYCLINE-INDUCED DIFFERENTIATION OF HUMAN ERYTHROLEUKEMIC CELLS

Aclacinomycin (ACLA) and doxorubicin (DOX) were used at subtoxic conce ntrations to induce erythroid differentiation in the human leukemic ce ll line K562, Cell hemoglobinization was accompanied by the increased expression of genes encoding gamma-globin and porphobilinogen deaminas e (PBGD), an enzyme of heme synthesis, By using run-on assays, ACLA wa s shown to induce an enhancement of the transcription of erythroid gen es, including gamma-globin, PBGD, erythropoietin receptor, and GATA-1 transcription factor, In contrast, in DOX-treated cells, the transcrip tion rate of these genes was unchanged in comparison with control cell s, In addition, inhibition of mRNA synthesis with actinomycin D indica ted that DOX induced an increased stability of PBGD and GATA-1 mRNAs, whereas ACLA did not affect the half-lives of these mRNAs, Because the increase in erythroid mRNA steady-state level in anthracycline-treate d cells was inhibited by cycloheximide, this suggests that transcripti onal activation in ACLA-treated cells and mRNA stabilization in DOX-tr eated cells were dependent on de novo protein synthesis, Finally, GATA -1 protein level was shown to be increased in ACLA-treated but not in DOX-treated cells, These two anthracyclines, although closely related in their structures, appeared to act as differentiation inducers by di stinct mechanisms. Indeed, erythroid gene expression was demonstrated to be regulated transcriptionally by ACLA and mainly posttranscription ally by DOX.