Kcs1-dependent inositol pyrophosphates promote DNA double-strand break repair via Pho80-Pho85 in budding yeast
- 1Universidade Federal de Sao Paulo
Abstract
The cleavage of membrane-bound phosphoinositides produces inositol polyphosphates (IPs) and pyrophosphates (PP-IPs), small water-soluble signaling molecules that are highly conserved in eukaryotes and play a critical role in cell metabolism. Loss of the inositol pyrophosphate kinase (PP-IPk) Kcs1 and its mammalian ortholog IP6K1 was previously shown to cause hypersensitivity to genotoxic stress and reduced homologous recombination (HR) repair. To identify the mechanism linking PP-IPs to DNA double-strand break (DSB) repair, we combined quantitative proteomics with biochemical, genetic, and cell-cycle analyses in budding yeast. We found that loss of Kcs1, but not the PP-IPk Vip1, caused increased sensitivity to the radiomimetic drug zeocin. kcs1{Delta} cells displayed persistent Rad53 signaling and elevated {gamma}-H2A levels, remaining arrested in G1/S during treatment and accumulating in G2/M for hours after damage removal. Unexpectedly, Kcs1-dependent PP-IPs promoted DSB repair independently of the core HR machinery and of cell-cycle stage. Quantitative proteomics revealed increased levels of PHO pathway proteins in zeocin treated kcs{Delta} cells, and deletion of the CDK inhibitor PHO81 substantially rescued zeocin hypersensitivity, indicating that constitutive inhibition of the Pho80-Pho85 cyclin-dependent kinase underlies the DNA repair defect caused by Kcs1 loss. This function of Pho80-Pho85 was mechanistically distinct from its canonical role in phosphate homeostasis, and partially independent of its connections to Ku80 regulation. Together, our findings identify Kcs1-dependent PP-IP signaling as a new upstream input controlling Pho80-Pho85 activity during the DNA damage response, establishing an HR-independent axis for genome maintenance and linking PP-IP metabolism to the DNA damage response in eukaryotic cells.
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BibTeX
@misc{panessa2026kcs1dependent,
title = {{Kcs1-dependent inositol pyrophosphates promote DNA double-strand break repair via Pho80-Pho85 in budding yeast}},
author = {G. M. Panessa and P. P. Sforsin and M. M. Wagner and G. Monteiro and M. B. Smolka and J. R. R. Cussiol},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.07.751851},
url = {https://www.biorxiv.org/content/10.64898/2026.10.07.751851v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Kcs1-dependent inositol pyrophosphates promote DNA double-strand break repair via Pho80-Pho85 in budding yeast
AU - G. M. Panessa
AU - P. P. Sforsin
AU - M. M. Wagner
AU - G. Monteiro
AU - M. B. Smolka
AU - J. R. R. Cussiol
PY - 2026
DA - 2026/10/07
PB - bioRxiv
DO - 10.64898/2026.10.07.751851
UR - https://www.biorxiv.org/content/10.64898/2026.10.07.751851v1
AB - The cleavage of membrane-bound phosphoinositides produces inositol polyphosphates (IPs) and pyrophosphates (PP-IPs), small water-soluble signaling molecules that are highly conserved in eukaryotes and play a critical role in cell metabolism. Loss of the inositol pyrophosphate kinase (PP-IPk) Kcs1 and its mammalian ortholog IP6K1 was previously shown to cause hypersensitivity to genotoxic stress and reduced homologous recombination (HR) repair. To identify the mechanism linking PP-IPs to DNA double-strand break (DSB) repair, we combined quantitative proteomics with biochemical, genetic, and cell-cycle analyses in budding yeast. We found that loss of Kcs1, but not the PP-IPk Vip1, caused increased sensitivity to the radiomimetic drug zeocin. kcs1{Delta} cells displayed persistent Rad53 signaling and elevated {gamma}-H2A levels, remaining arrested in G1/S during treatment and accumulating in G2/M for hours after damage removal. Unexpectedly, Kcs1-dependent PP-IPs promoted DSB repair independently of the core HR machinery and of cell-cycle stage. Quantitative proteomics revealed increased levels of PHO pathway proteins in zeocin treated kcs{Delta} cells, and deletion of the CDK inhibitor PHO81 substantially rescued zeocin hypersensitivity, indicating that constitutive inhibition of the Pho80-Pho85 cyclin-dependent kinase underlies the DNA repair defect caused by Kcs1 loss. This function of Pho80-Pho85 was mechanistically distinct from its canonical role in phosphate homeostasis, and partially independent of its connections to Ku80 regulation. Together, our findings identify Kcs1-dependent PP-IP signaling as a new upstream input controlling Pho80-Pho85 activity during the DNA damage response, establishing an HR-independent axis for genome maintenance and linking PP-IP metabolism to the DNA damage response in eukaryotic cells.
ER -