# Spontaneous replication fork collapse regulates telomere length homeostasis in wild type yeast

> **NIH NIH R01** · SALK INSTITUTE FOR BIOLOGICAL STUDIES · 2021 · $380,000

## Abstract

Project Summary/Abstract:
Telomeres present unique challenges for genomes with linear chromosomes, including the inability of the
semi-conservative DNA replication machinery to fully duplicate the ends of linear molecules. This is solved
in virtually all eukaryotes by the enzyme telomerase, through the addition of telomeric repeats onto
chromosome ends. It is widely assumed that the primary site of action for telomerase is the single-stranded
G-rich overhang at the ends of chromosomes, formed after DNA replication is complete. A newly developed
assay that monitors spontaneous monitor fork collapse at an interstitial telomeric tract has demonstrated there
is a second substrate for telomerase in wild type yeast, which is a collapsed fork generated during replication
of duplex telomeric DNA. Newly collapsed forks are extensively elongated by telomerase in a single cell
division, indicating that a major source of newly synthesized telomeric repeats in wild type cells occurs at
collapsed forks. Furthermore, the ability of telomerase to elongate newly collapsed forks is dependent on fork
remodeling proteins. In parallel, a re-examination of the role of a telomere-dedicated RPA-like complex (t-
RPA) in budding yeast argues that this complex facilitates lagging strand synthesis during duplex DNA
replication, rather than protecting telomeres in from unregulated resection. Additional data argues that this
complex collaborates with the canonical RPA complex to stabilize replication forks during duplex telomeric
DNA replication. Collectively, these observations provide a substantial challenge to current models for how
telomere homeostasis is maintained in wild type yeast. This application tests the model that the activity of
telomerase in response to spontaneous fork collapse is a major determinant of telomere length regulation.
Aim 1 will test the hypothesis that telomerase activity at newly collapsed forks proceeds through a regulatory
pathway distinct from how telomerase engages fully replicated chromosome termini. Aim 2 will test the
hypothesis that two RPA complexes, one dedicated to the leading strand (RPA) and the other (t-RPA) bound
to the lagging strand, collaborate to promote stabilization of the fork during replication of duplex telomeric
DNA. The third Aim will examine a new role for the canonical RPA complex in regulating telomerase, through
surfaces that are highly conserved from yeast to humans.

## Key facts

- **NIH application ID:** 10236201
- **Project number:** 1R01GM142173-01
- **Recipient organization:** SALK INSTITUTE FOR BIOLOGICAL STUDIES
- **Principal Investigator:** Victoria Lundblad
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $380,000
- **Award type:** 1
- **Project period:** 2021-04-01 → 2025-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10236201

## Citation

> US National Institutes of Health, RePORTER application 10236201, Spontaneous replication fork collapse regulates telomere length homeostasis in wild type yeast (1R01GM142173-01). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10236201. Licensed CC0.

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