Adolph, M. B. | Search bioRxiv

bioRxiv2026

STING causes replication stress and nascent DNA degradation via SAMHD1

STING is a key innate immune adaptor, classically activated by cytosolic DNA via cGAS-cGAMP to induce type I interferon signaling. While its cytoplasmic role is well defined, recent studies reveal that STING participates in non-canonical signaling pathways and localizes at the nuclear envelope and chromatin, where its functions remain poorly understood. In Hutchinson Gilford Progeria Syndrome (HGPS), a premature aging disease caused by expression of lamin A mutant protein named progerin, STING accumulates in the nucleus and drives chronic inflammation. Here, we show that replication stress (RS) is a trigger of STING nuclear accumulation and binding to chromatin. In addition, we uncover a previously unrecognized role for nuclear STING binding to nascent DNA and promoting RS in progeria and tumor cells. Mechanistically, STING contributes to replication fork slowing and stalling by limiting dNTPs availability. In addition, STING hinders replication fork protection/stability upon stalling, by facilitating MRE11-mediated nascent DNA degradation (NDD). We also find that STING contribution to depletion of dNTPs and NDD is mediated by SAMHD1. As such, SAMHD1 knockdown phenocopies STING abrogation in progeria cells and rescues replication fork speed and stability in STING-overexpressing tumor cells. These findings define a pathological STING-SAMHD1 axis that drives RS and genome instability in both progeria cells and tumor cells with elevated STING activity, uncovering a feedforward loop between innate immune signaling and impaired DNA replication. HighlightsO_LIReplication stress in human fibroblasts triggers STING nuclear accumulation and an IFN response C_LIO_LISTING upregulation and nuclear accumulation hinders replication in progeria fibroblasts and U2OS tumor cells C_LIO_LISTING-induced replication stress features fork slowing/stalling and nascent DNA degradation C_LIO_LISTING-induced fork slowing/stalling is mediated by the dNTPase SAMHD1 C_LIO_LISAMHD1-enabled MRE11 activity is responsible for STING-induced nascent DNA degradation C_LI

cell biology↗

bioRxiv2024

Strand dependent bypass of DNA lesions during fork reversal by ATP-dependent translocases SMARCAL1, ZRANB3, and HLTF

Withdrawal StatementThe authors have withdrawn this manuscript because they identified problems with how some figure panels were processed. Those experiments will be repeated before deposition of a new manuscript. Therefore, the authors do not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding authors.

biochemistry↗

bioRxiv2023

CRISPR-dependent base editing screens identify separation of function mutants of RADX with altered RAD51 regulatory activity

RAD51 forms nucleoprotein filaments to promote homologous recombination, replication fork reversal, and fork protection. Numerous factors regulate the stability of these filaments and improper regulation leads to genomic instability and ultimately disease including cancer. RADX is a single stranded DNA binding protein that modulates RAD51 filament stability. Here, we utilize a CRISPR-dependent base editing screen to tile mutations across RADX to delineate motifs required for RADX function. We identified separation of function mutants of RADX that bind DNA and RAD51 but have a reduced ability to stimulate its ATP hydrolysis activity. Cells expressing these RADX mutants accumulate RAD51 on chromatin, exhibit replication defects, have reduced growth, accumulate DNA damage, and are hypersensitive to DNA damage and replication stress. These results indicate that RADX must bind RAD51 and promote RAD51 ATP turnover to regulate RAD51 and genome stability during DNA replication.

molecular biology↗