[Segments initiating replication of the dihydrofolate reductase domain and the DNA fragment DARC146 interact with the same nuclear proteins].

Comparison analysis was made of the putative replication origin DARC146 and the origin determined in the DNFR domain of CHO cells. We failed to observe extensive homology between these two sequences. However, several short (8-10 bp) areas of homology were identified. Some of them are binding sites for nuclear proteins. As shown by GM and competition experiments, both origins contain high-affinity binding sites for the transcription-replication factor Oct-1 and for two unknown nuclear factors. The two unknown nuclear factors bound to TCTCTTA and CACTTAG nucleotides. The binding sites for these proteins are located at a short distance from each other. This fact suggests interaction between these polypeptides. Measurement of DNA-binding activity of Oct-1 during the cell cycle of proliferating hepatocyte demonstrated that the binding activity of Oct-1 protein increased before initiation of DNA synthesis. The results of this report suggest that Oct-1 and two other nuclear proteins participate in the regulation of mammalian DNA replication. The results published early indicated the presence of an unusual DNA structure (bent DNA) in both origins under study. We suggest that these common elements of the origins regulate their activation.