Geminin inhibits DNA replication licensing by sterically blocking CDT1-MCM2 interactions
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Author(s)
Type
Journal Article
Abstract
DNA replication is tightly regulated to occur once per cell cycle, with the MCM2-7 helicase loaded onto replication origins only during G1-phase. In higher eukaryotes, geminin negatively regulates this process during S-, G2- and M-phases by binding the essential licensing factor CDT1.
Although geminin’s function is crucial for genomic stability, its inhibitory mechanism remains elusive. Here, we utilise a fully reconstituted human DNA replication licensing assay to dissect geminin’s role. AlphaFold modelling provides structural insights into an N-terminal CDT1-binding
helix of geminin, which proves essential for inhibition. Structural docking of the CDT1-geminin complex into the ORC-CDC6-CDT1-MCM2-7 (OCCM) assembly shows that geminin’s long coiled-coil domain sterically clashes with the MCM2 C-terminus, rather than directly blocking
CDT1 binding to ORC-CDC6-MCM2-7. Shortening the coiled-coil preserves geminin dimerisation and CDT1 binding but abolishes inhibition, confirming its mechanistic role. Surprisingly, geminin is not able to fully inhibit DNA licensing. However, CDK1/2-cyclin A can partially inhibit DNA licensing and, in conjunction with geminin, result in a complete block. These findings uncover geminin’s steric inhibitory mechanism and suggest that a dual CDK-geminin axis controls human DNA replication.
Although geminin’s function is crucial for genomic stability, its inhibitory mechanism remains elusive. Here, we utilise a fully reconstituted human DNA replication licensing assay to dissect geminin’s role. AlphaFold modelling provides structural insights into an N-terminal CDT1-binding
helix of geminin, which proves essential for inhibition. Structural docking of the CDT1-geminin complex into the ORC-CDC6-CDT1-MCM2-7 (OCCM) assembly shows that geminin’s long coiled-coil domain sterically clashes with the MCM2 C-terminus, rather than directly blocking
CDT1 binding to ORC-CDC6-MCM2-7. Shortening the coiled-coil preserves geminin dimerisation and CDT1 binding but abolishes inhibition, confirming its mechanistic role. Surprisingly, geminin is not able to fully inhibit DNA licensing. However, CDK1/2-cyclin A can partially inhibit DNA licensing and, in conjunction with geminin, result in a complete block. These findings uncover geminin’s steric inhibitory mechanism and suggest that a dual CDK-geminin axis controls human DNA replication.
Date Issued
2025-12-10
Date Acceptance
2025-11-17
Citation
Nature Communications, 2025, 16
ISSN
2041-1723
Publisher
Nature Portfolio
Journal / Book Title
Nature Communications
Volume
16
Copyright Statement
© The Author(s) 2025 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
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Publication Status
Published
Article Number
11040
Date Publish Online
2025-12-09