Sld7, an Sld3-associated protein required for efficient chromosomal DNA replication in budding yeast.
Tanaka, T., Umemori, T., Endo, S., Muramatsu, S., Kanemaki, M., Kamimura, Y., Obuse, C. and Araki, H.
EMBO J. 30, 2019 - 2030. (2011)  DOI: 10.1038/emboj.2011.115.2011

  Chromosomal DNA is replicated from the specific site, called a replication origin during the cell cycle. At replication origins, many proteins assemble and form the replication machinery to start DNA synthesis. To synthesize a whole chromosomal DNA, the machinery should dissociate from origins and move along the chromosome. It suggests that the proteins alter its affinity to origins. Budding yeast Cdc45 and Sld3 proteins associate with replication origins in a mutually dependent manner. However, Cdc45, as a component of the replication machinery, dissociates from origins and moves with the replication fork while Sld3 simply dissociates from origins. In this paper, we reported a new replication protein, Sld7. This protein forms a tight complex with Sld3 through the cell cycle. Although Sld7 is not essential for cell growth, its absence reduces the level of cellular Sld3, delays the dissociation from origins of GINS, a component of the replication machinery, and slows S-phase progression. Furthermore, Sld7 reduces the affinity of Sld3 to Cdc45. These results suggest that Sld7 is required for proper dissociation of Sld3 from origins at the initiation of DNA replication. It further implys that dissociation process as well as association process is important for efficient initiation of DNA replication.

The initiation of DNA replication. Proteins assemble on the replication origin (red oval) and form a replication machinery (blue oval). When the Sld3-Sld7 complex is dissociated from the origin, the replication machinery starts DNA replication and separates from the origin.