Human CST promotes telomere duplex replication and general replication restart after fork stalling

• Published in: The EMBO journal Vol. 31; no. 17; pp. 3537 - 3549
• Main Authors: Stewart, Jason A, Wang, Feng, Chaiken, Mary F, Kasbek, Christopher, Chastain, Paul D, Wright, Woodring E, Price, Carolyn M
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 29.08.2012; John Wiley & Sons, Ltd; Springer Nature B.V; Nature Publishing Group
• Subjects: Cell Line, Tumor; CTC1; Deoxyribonucleic acid; Depletion; DNA; DNA Replication; EMBO13; Gene Knockdown Techniques; Genomic Instability; Genomics; Humans; Mammals; Molecular biology; replication origin; STN1; Telomerase; Telomere - metabolism; Telomere-Binding Proteins - genetics; telomeres; Telomeric Repeat Binding Protein 1 - genetics; CTC1; DNA replication; STN1; replication origin; telomeres
• ISSN: 0261-4189; 1460-2075; 1460-2075
• DOI: 10.1038/emboj.2012.215

Mammalian CST (CTC1‐STN1‐TEN1) associates with telomeres and depletion of CTC1 or STN1 causes telomere defects. However, the function of mammalian CST remains poorly understood. We show here that depletion of CST subunits leads to both telomeric and non‐telomeric phenotypes associated with DNA replication defects. Stable knockdown of CTC1 or STN1 increases the incidence of anaphase bridges and multi‐telomeric signals, indicating genomic and telomeric instability. STN1 knockdown also delays replication through the telomere indicating a role in replication fork passage through this natural barrier. Furthermore, we find that STN1 plays a novel role in genome‐wide replication restart after hydroxyurea (HU)‐induced replication fork stalling. STN1 depletion leads to reduced EdU incorporation after HU release. However, most forks rapidly resume replication, indicating replisome integrity is largely intact and STN1 depletion has little effect on fork restart. Instead, STN1 depletion leads to a decrease in new origin firing. Our findings suggest that CST rescues stalled replication forks during conditions of replication stress, such as those found at natural replication barriers, likely by facilitating dormant origin firing. The mammalian CTC1‐STN1‐TEN1 complex functions not only in maintenance and replication of telomeres, but also has a surprising genome‐wide role in restart after replication fork stalling.