The DNA damage response pathway contributes to the stability of chromosome III derivatives lacking efficient replicators.

In eukaryotic chromosomes, DNA replication initiates at multiple origins. Large inter-origin gaps arise when several adjacent origins fail to fire. Little is known about how cells cope with this situation.

Identification of mutations that decrease the stability of a fragment of Saccharomyces cerevisiae chromosome III lacking efficient replicators.

Eukaryotic chromosomes are duplicated during S phase and transmitted to progeny during mitosis with high fidelity. Chromosome duplication is controlled at the level of replication initiation, which occurs at cis-acting replicator sequences that are spaced at intervals of approximately 40 kb along the chromosomes of the budding yeast Saccharomyces cerevisiae. Surprisingly, we found that derivatives of yeast chromosome III that lack known replicators were replicated and segregated properly in at least 96% of cell divisions.

Linear derivatives of Saccharomyces cerevisiae chromosome III can be maintained in the absence of autonomously replicating sequence elements.

Replication origins in Saccharomyces cerevisiae are spaced at intervals of approximately 40 kb. However, both measurements of replication fork rate and studies of hypomorphic alleles of genes encoding replication initiation proteins suggest the question of whether replication origins are more closely spaced than should be required. We approached this question by systematically deleting replicators from chromosome III.