Multiple Orientation-Dependent, Synergistically Interacting, Similar Domains in the Ribosomal DNA Replication Origin of the Fission Yeast, Schizosaccharomyces pombe

ABSTRACT

Previous investigations have shown that the fission yeast,Schizosaccharomyces pombe, has DNA replication origins (500 to 1500 bp) that are larger than those in the budding yeast,Saccharomyces cerevisiae (100 to 150 bp). Deletion and linker substitution analyses of two fission yeast origins revealed that they contain multiple important regions with AT-rich asymmetric (abundant A residues in one strand and T residues in the complementary strand) sequence motifs. In this work we present the characterization of a third fission yeast replication origin, ars3001, which is relatively small (∼570 bp) and responsible for replication of ribosomal DNA. Like previously studied fission yeast origins,ars3001 contains multiple important regions. The three most important of these regions resemble each other in several ways: each region is essential for origin function and is at least partially orientation dependent, each region contains similar clusters of A+T-rich asymmetric sequences, and the regions can partially substitute for each other. These observations suggest that ars3001function requires synergistic interactions between domains binding similar proteins. It is likely that this requirement extends to other fission yeast origins, explaining why such origins are larger than those of budding yeast.

ACKNOWLEDGMENTS

We are grateful to J. Aquiles Sanchez for pioneering the study ofS. pombe rDNA replication in our laboratory; to William Burhans and David Kowalski for comments on the manuscript; and to Debbie Mahoney, Karuna Sharma, and Martin Weinberger for constructive criticism throughout this study.

This research was supported by Public Health Service grant GM49294 from the National Institute of General Medical Sciences and by a grant from the Buffalo Foundation, with additional support from shared resources of the Roswell Park Cancer Center Support, grant P30 CA16056.