Human Tumor Cell Lines Distal CCAAT Box of Human Thymidine Kinase Promoter in Constitutive Overexpression of DNA Binding Activity to the Updated Version

We have used the sequence of the cell-cycle regulatory region of human thymidine kinase promoter to study the DNA-protein interaction in hu man 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 kinase CCAAT-binding activity was serum or independent in human tu mor cells but serum dependent in normal human diploid fibroblasts. Our results present the fact that the constitutive interaction of CCAAT-binding factor with the promoter of a cell growth-controlled gene, such as thymi dine kinase, is consistent with the loss of stringent cell growth regulation associated with tumorigenic phenotype.