CLONING OF CDNA WITH POSSIBLE TRANSCRIPTION FACTOR ACTIVITY AT THE G(1)-S PHASE-TRANSITION IN HUMAN FIBROBLAST CELL-LINES

Normal human fibroblasts have a finite proliferative capacity in vitro . Thus, immortalization of human cells is associated with cellular agi ng. We have established an immortalization-sensitive cell line from fi broblasts of Wilms' tumor patients which have a partial deletion of ch romosome 11 p. This cell line was easily immortalized by introducing S V40T. By differential hybridization using both SV40T-introduced crisis cells and young cells, we cloned a gene that was highly expressed in 11 p- cells at the time of the crisis and named this gene C-1. Nucleot ide sequence analysis of C-1 revealed that it contains a helix-loop-he lix domain, indicating that it may be a transcription factor. Expressi on of the C-1 gene was transiently induced early in the G(0)-to-S phas e transition in two normal human (OUMS-24 and HSF-412) and a non-tumor igenic immortal human (OUMS-24F) fibroblast cell lines, while the othe r immortal SUSM-1 cells highly expressed the C-1 gene in the middle G( 1) phase. These results suggest that the C-1 gene product may function as a transcription factor related to the cell cycle.