Control of ATP-Dependent Binding of Saccharomyces cerevisiae Origin Recognition Complex to Autonomously Replicating DNA Sequences

Eukaryotic origin recognition complexes (ORCs) play pivotal roles in the initiation of chromosomal DNA replication. ORC from the yeast, Saccharomyces cerevisiae, recognizes and binds replication origins in the late G1 phase and the binding has profound implications in the progression of the cell cycle to the S-phase. Therefore, we have quantitatively analyzed the mechanism of recognition and interaction of the yeast ORC with various elements of a yeast origin of DNA replication, the autonomously replicating sequence 1 (ARS1). ORC bound all four individual A and B elements of ARS1 with reasonably high affinities. However, the highest affinity binding was observed with a DNA sequence containing both the A and B1 elements. In addition, ATP and ADP significantly modulated the binding of ORC to the combined elements as well as modulating the binding of ORC to the element A alone or in combination with the B1 element. However, binding of ORC to individual B1, B2, and B3 elements was not responsive to nucleotides. Thus, the consensus ARS sequence in element A appeared to play a pivotal role in the ATP-dependent binding of ORC to ARS1 and likely in other ARSs or origins of DNA replication.