CONSTITUTIVE OVEREXPRESSION OF DNA-BINDING ACTIVITY TO THE DISTAL CCAAT BOX OF HUMAN THYMIDINE KINASE PROMOTER IN HUMAN TUMOR-CELL LINES

We have used the sequence of the cell-cycle regulatory region of human thymidine kinase promoter to study the DNA-protein interaction in hum an tumor and normal cells. By performing band-shift assays and DNase I footprint analysis, we have demonstrated that human tumor cells exhib ited an elevated level of binding activity to the distal CCAAT box of human thymidine kinase promoter. The expression of human thymidine kin ase CCAAT-binding activity was serum or independent in human tumor cel ls but serum dependent in normal human diploid fibroblasts. Our result s present the fact that the constitutive interaction of CCAAT-binding factor with the promoter of a cell growth-controlled gene, such as thy midine kinase, is consistent with the loss of stringent cell growth re gulation associated with tumorigenic phenotype.