Identification of cellular differentiation-dependent nuclear factors that bind to a human gene for thymidylate...

Three nuclear factors were identified that interact with sequences in the 5'-upstream region of the human thymidylate synthase gene. Two of these factors interact with a sequence around the initiation codon of the thymidylate synthase gene. The amounts of these two factors changed dramatically as human promyelocytic leukemia HL-60 cells differentiated into macrophage-like cells by the treatment with 1,25-dihydroxyvitamin D3. The change was closely correlated with the decrease in the amount of thymidylate synthase mRNA during the differentiation. These findings suggest that the specific nuclear factors are involved in the regulation of the expression of human thymidylate synthase gene during the differentiation of HL-60 cells.