[The interaction of nuclear proteins with bent DNA located in an autonomously replicating DARC146 sequence]

The binding of nuclear proteins to a DARC146 DNA fragment is described. The DARC146 was isolated from a complex form of DNA polymerase alpha. BrdUrd substitution experiments indicate that DARC146 can support an autonomous replication in mammalian cells. Three AAA blocks separated by 10 nucleotides were identified in the DARC146 sequence. Measuring electrophoretical mobility under appropriate conditions showed that these AAA blocks form a bent DNA. We have used a synthetic oligonucleotide covering the bent DNA to study the interaction of nuclear proteins with this DNA region. Four DNA-protein complexes with the bent DNA region were registered. One of them is formed by binding nuclear factor p65 to TCTATTA nucleotides. The molecular weight and binding site of p65 are very similar to those of c-myc protein. However, antibodies against c-myc protein exert no effect on the formation of the p65-DNA complex. We suggest that p65 is an unknown nuclear factor.