3'-AZIDO-3'-DEOXYTHYMIDINE INHIBITS ERYTHROID-SPECIFIC TRANSCRIPTION FACTORS IN HUMAN ERYTHROID K562 LEUKEMIA-CELLS

The present study examines genetic mechanism(s) possibly involved in t he observed 3'-azido-3'-deoxythymidine (AZT)-induced inhibition of glo bin gene transcription by evaluating the direct phenotypic erythroid e ffects of AZT on erythroid-specific transcription factors which regula te globin gene promoters. In vitro binding of GATA-1 or NFE-2 to its c onsensus sequence was decreased in the presence of AZT reaching a maxi mum inhibition as early as 24 h after AZT treatment, Nuclear extracts from butyric acid-induced K562 cells treated with an IC50 concentratio n of AZT exhibited a decrease in GATA-1 and NFE-2 binding by approxima tely 30% and 35%. In contrast, 2',3'-dideoxycytidine which inhibits ce ll growth without affecting hemoglobin synthesis, had no effect on bin ding of GATA-1 and NFE-2 factors. Northern blot analysis revealed a 25 % decrease by AZT in GATA-1 mRNA steady-state levels at 24 h and this inhibitory effect was maintained until 72 h after drug addition, A sim ilar decrease in NFE-2 mRNA steady-state levels was observed at 72 h a fter AZT treatment. This study suggests that AZT inhibition of erythro id differentiation is subsequent to a decrease of nuclear factors gene expression which affect their DNA binding.