[DNA fragment DARC146 from a complex form of DNA polymerase alpha contains several nuclear protein binding segments].

Earlier, a number of DNA fragments were identified in the complex form of DNA polymerase alpha. One of them, DARC146, can support autonomous replication in mammalian cells. We have subcloned 146 bp from DARC146 (here called DARC146). This fragment has an ability to replicate autonomously in mammalian cells. This ability permits one to speak about DARC146 as a putative replication origin. From this conclusion, we suggest that all signals for initiation of DNA synthesis are located on the nucleotide sequence under study. Here, we have shown that the nuclear extract contains four polypeptides binding specifically to synthetic oligonucleotides covering the AT-rich region of the DARC146 sequence. The first protein is Oct-1, a nuclear transcription-replication factor. The second protein (named p65) binds to the TCTCTTA site of the DARC146 nucleotide sequence. There are two sites for Oct-1 protein and two sites for p65 in the DARC146 fragment. Octamer motifs and sites for p65 are located tandemly side by side. Moreover, we identified 28kDa polypeptide from nuclear matrix which bound to DARC146. Based upon the data presented, we suggest a hypothetical model of the pre-initiation state of the DARC146 sequence.