What the study found
The study found that the human CTF18–RFC clamp loader has distinctive structural features while bound to PCNA, the sliding clamp that helps DNA polymerases work processively. The authors report that its regulatory Ctf8 and Dcc1 subunits are flexibly tethered, and that the RFC module is seen in an autoinhibited state similar to canonical RFC.
Why the authors say this matters
The authors conclude that these structural features provide insight into how CTF18–RFC loads PCNA and supports leading strand synthesis by Pol ε, the leading strand DNA polymerase. The study suggests that understanding this complex helps explain an early step in the clamp-loading reaction.
What the researchers tested
The researchers used cryo-EM, a structural imaging method that studies frozen, electron-microscope specimens, to characterize the human CTF18–RFC complex and its interaction with PCNA. They examined the complex at 2.9 Å resolution and assessed the effects of deleting a novel β-hairpin in the RFC1 subunit.
What worked and what didn't
The cryo-EM data supported that Ctf8 and Dcc1 are flexibly tethered to the RFC module. The structure showed RFC bound to PCNA in an autoinhibited conformation, while RFC1 was anchored through a low-affinity PIP box and a novel β-hairpin interaction with RFC5. Deleting the β-hairpin impaired complex stability, slowed clamp loading, and decreased the rate of primer synthesis by Pol ε.
What to keep in mind
The abstract does not describe broader limitations beyond the structural and experimental scope reported here. The findings are based on cryo-EM analysis of the human CTF18–RFC complex and a deletion test of one β-hairpin region.
Key points
- Human CTF18–RFC was structurally characterized while bound to PCNA.
- Ctf8 and Dcc1 were reported as flexibly tethered regulatory subunits.
- The RFC module bound PCNA in an autoinhibited conformation similar to canonical RFC.
- RFC1 was anchored by a low-affinity PIP box and a novel β-hairpin interaction with RFC5.
- Deleting the β-hairpin weakened complex stability, slowed clamp loading, and reduced primer synthesis by Pol ε.
Disclosure
- Research title:
- CTF18–RFC structure shows distinctive PCNA-loading features
- Authors:
- Giuseppina R. Briola, Mohammad Tehseen, Amani Al-Amodi, Grace Young, Ammar Usman Danazumi, Phong Quoc Nguyen, Christos G. Savva, Mark Hedglin, Samir M Hamdan, Alfredo De Biasio
- Institutions:
- King Abdullah University of Science and Technology, King Abdullah University of Science and Technology, King Abdullah University of Science and Technology, King Abdullah University of Science and Technology, King Abdullah University of Science and Technology, King Abdullah University of Science and Technology, King Abdullah University of Science and Technology, King Abdullah University of Science and Technology, Pennsylvania State University, Pennsylvania State University
- Publication date:
- 2026-02-23
- OpenAlex record:
- View
- Image credit:
- Photo by Nicola Narracci on Pexels · Pexels License
Get the weekly research newsletter
Stay current with peer-reviewed research without reading academic papers — one filtered digest, every Friday.