In order to gain a better understanding of how RPA functions in DNA replication, repair, and cell cycle regulation and to identify other potential functions of RPA, this study performed a yeast two-hybrid screen using the yeast 70 kDa subunit, Replication Factor A1 (Rfa1), as a bait protein.
Analysis of 136 interaction candidates resulted in the identification of 37 potential interacting partners, including the cell cycle regulatory protein and DNA damage clamp loader Rad24. The Rfa1-Rad24 interaction is not dependent on ssDNA binding; however, this interaction appears affected by DNA damage. The regions of both Rfa1 and Rad24, important for this interaction, were identified; and the region of Rad24 identified is distinct from the region reported to be important for its interaction with Rfc2 5. This suggests that Rad24-Rfc2-5 (Rad24-RFC) recruitment to DNA damage substrates by RPA occurs, at least partially, through an interaction between the N terminus of Rfa1 and the C terminus of Rad24. The predicted structure and location of the Rad24 C-terminus is consistent with a model in which RPA interacts with a damage substrate, loads Rad24-RFC at the 5' junction, and then releases the Rad24-RFC complex to allow for proper loading and function of the DNA damage clamp. (Publisher abstract modified)