A yeast chromosomal origin of DNA replication defined by multiple functional elements

Although it has been demonstrated that discrete origins of DNA replication exist in eukaryotic cellular chromosomes, the detailed organization of a eukaryotic cellular origin remains to be determined. Linker substitution mutations were constructed across the entire Saccharomyces cerevisiae chromosomal origin, ARS1. Functional studies of these mutants revealed one essential element (A), which includes a match to the ARS consensus sequence, and three additional elements (B1, B2, and B3), which collectively are also essential for origin function. These four elements arranged exactly as in ARS1, but surrounded by completely unrelated sequence, functioned as an efficient origin. Element B3 is the binding site for the transcription factor-origin binding protein ABF1. Other transcription factor binding sites substitute for the B3 element and a trans-acting transcriptional activation domain is required. The multipartite nature of a chromosomal replication origin and the role of transcriptional activators in its function present a striking similarity to the organization of eukaryotic promoters.