Mechanism of RPA phosphocode priming and tuning by Cdk1/Wee1 signaling circuit

ABSTRACT: Replication protein A (RPA) is a heterotrimeric single-strand DNA binding protein that is integral to DNA metabolism. Segregation of RPA functions in response to DNA damage is fine-tuned by hyperphosphorylation of the RPA32 subunit that is dependent on Cyclin-dependent kinase (Cdk)-mediated priming phosphorylation at the Ser-23 and Ser-29 sites. However, the mechanism of priming-driven hyperphosphorylation of RPA and the modulation of cell cycle progression by the RPA-Cdk axis remain unresolved. Here, we uncover that the RPA70 subunit is also phosphorylated by Cdk1 at Thr-191. This modification is crucial for G2 to M phase transition. This function is enacted through reciprocal regulation of Cdk1 activity through a feedback circuit espoused by stabilization of Wee1 kinase. The Thr-191 phosphosite on RPA70 is also crucial for priming hyperphosphorylation of RPA32 in response to DNA damage. Structurally, phosphorylation by Cdk1 primes RPA by reconfiguring the domains to release the N-terminus of RPA32 and the two protein-interaction domains. These configurational changes markedly enhance the efficiency of multisite phosphorylation by other kinases independent of RPA-ssDNA interactions. Our findings establish a unique phosphocode-dependent feedback mechanism between RPA and RPA-regulating kinases that is fine-tuned to enact distinct bipartite functions in cell cycle progression and DNA damage response.

INSTRUMENT(S):

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Monika Tokmina-Lukaszewska  

LAB HEAD: Edwin Antony

PROVIDER: PXD068080 | Pride | 2026-01-12

REPOSITORIES: Pride