Biology subjects

Heyza, J.

Publications and source records attributed to Heyza, J..

4 recordsLinked to original sources

bioRxiv2026

DNA Polymerase Beta Catalytic and Fidelity Mutations Drive Platinum Specific Drug Sensitivity

With the advent of genome sequencing and its widespread use in the clinic, there is a great need to identify mutational biomarkers that predict therapeutic responses. DNA polymerase Beta (Pol{beta}) and the base excision repair (BER) pathway have been previously implicated as modulators of response to platinum-based chemotherapies and are mutated in as high as 30% of cancers. Here, we show in a triple-negative breast cancer (TNBC) model that two classes of mutations in Pol{beta}, reduced catalytic activity (E295K and D256A mutation) and reduced fidelity (I260M), are sufficient to drive cisplatin and carboplatin-specific sensitivity. Cellular response to oxaliplatin in these Pol{beta} mutant models is minimal relative to cisplatin and carboplatin. Additionally, we show that sensitivity is associated with reduced repair of both platinum-induced DNA intrastrand adducts and interstrand crosslinks (ICLs). Downregulation of the upstream BER factor uracil DNA glycosylase (UNG) reverses drug sensitivity consistent with these Pol{beta} mutations negatively impacting ICL DNA repair to drive drug sensitivity. In addition, intrastrand adduct repair readout indicates these lesions also play a role in the sensitivity observed in Pol{beta} mutant models. In vivo studies demonstrate a significant effect on tumor growth delay with cisplatin treatment in tumor xenografts harboring Pol{beta} mutations. These results support the potential for using Pol{beta} mutations as predictive biomarkers for cisplatin and carboplatin therapies in the clinical setting.

Cancer Biology↗

bioRxiv2026

A universal regulatory mechanism for prevention of replication restart from RNA:DNA hybrids

RNA:DNA hybrids form across all genomes. In vitro studies showed that these structures can be used to restart stalled replication forks, especially upon replication-transcription conflicts, however, this has not been tested in vivo. Here, we identify a mechanism that prevents replication restart from hybrids within cells. We identified the tRNA ligase, AsnRS, as a regulator of replication restart from hybrids at conflict regions in Bacillus subtilis. We determined that the DNA translocase Mfd and DNA polymerase PolA play key roles in this pathway. We unraveled a mechanism whereby Mfd removes RNA Polymerases, exposing 3 ends of the RNAs within hybrids. These 3 ends are then capped by AsnRS, preventing restart by PolA. Remarkably, the mammalian homologs of AsnRS, NARS1 and NARS2, fully complement the AsnRS phenotypes in bacteria. We propose that this is a universally conserved mechanism that prevents untimely replication initiation outside of origins from bacteria to humans.

genetics↗

bioRxiv2025

Ku limits aberrant mRNA splicing promoted by intronic antisense Alu elements

Alu elements are short repeats that occupy approximately 10% of the human genome 1,2. Saturation of primate genomes with Alu sequences occurred at the prosimian/new-world monkey evolutionary juncture. Alu elements have clearly driven unique aspects of higher primate evolution, but their presence can be detrimental to genomic stability 3. The expansion of Alu sequences in the genomes of higher primates precisely coincides with a substantial increase in the ubiquitous expression of the three polypeptides of the DNA-dependent protein kinase (DNA-PK), the Ku70/80 heterodimer and DNA-PKcs 4. Previous work suggests that the elevated levels of Ku70/80 are required to prevent the activation of innate immune signaling pathways triggered by RNA molecules derived from Alu elements 5. Here we demonstrate that Ku ablation dramatically alters mRNA splicing, by allowing the use of alternative splice sites contained in intronic antisense Alu elements, which are known to directly associate with Ku70/80 5. Dysregulation of mRNA splicing precedes cell death and preferentially impacts genes involved in essential RNA metabolism processes, including splicing and ribosome biogenesis, likely impacting cell viability. In addition, we demonstrate that cell death after Ku70 depletion cannot be rescued by expression of its prosimian homologue, which suggests that primate Ku70 has evolved specific molecular features to suppress deleterious effects of an Alu element rich genome. We propose a model in which Ku binding of antisense Alu elements in introns of nascent RNAs modulates the use of alternative splice sites to balance beneficial and detrimental contributions of Alu repeats within primate genomes.

molecular biology↗

bioRxiv2020

Chemical exhaustion of RPA in cancer treatment

Replication protein A (RPA) plays essential roles in DNA replication, repair, recombination and the DNA-damage response (DDR). We have developed second generation RPA inhibitors (RPAis) that block the RPA-DNA interaction. These DNA-binding inhibitors (DBis) can elicit a state of cellular RPA exhaustion resulting in single agent in vitro anticancer activity across a broad spectrum of cancers and in vivo activity in two non-small cell lung cancer models. The cellular response to RPAi treatment suggests a threshold exists before RPA inhibition induces cell death. Chemical RPA exhaustion potentiates the anticancer activity of other DDR inhibitors as well as traditional DNA damaging cancer therapeutics. Consistent with the chemical RPA exhaustion model, we demonstrate that the effects of RPAi on replication fork dynamics and DNA damage signaling are similar to other known DDR inhibitors. In accordance with the RPA threshold model, retrospective analysis of lung cancer patient data demonstrates high RPA expression as a negative prognostic biomarker for overall survival in smoking-related lung cancers. Similarly, relative expression of RPA is a predictive marker for response to chemotherapy. These observations are consistent with the increase in RPA expression serving as an adaptive mechanism that allows tolerance of the genotoxic stress resulting from carcinogen exposure. These data demonstrate a unique mechanism of action of RPAis eliciting a state of RPA exhaustion that impacts the DDR and may provide an effective therapeutic option for difficult to treat lung cancers. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=130 SRC="FIGDIR/small/404640v1_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@d662e4org.highwire.dtl.DTLVardef@f68b11org.highwire.dtl.DTLVardef@241c0corg.highwire.dtl.DTLVardef@ad7398_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗