Biology subjects

Kopasz, A. G.

Publications and source records attributed to Kopasz, A. G..

2 recordsLinked to original sources

bioRxiv2026

Intrahepatic reporter assay reveals leaky somatic blockade of L1 retrotransposition in mice

Long interspersed element-1 (LINE-1, L1) retrotransposition has long been proposed to occur in somatic tissues, yet direct experimental evidence distinguishing adult somatic events from early embryonic insertions has remained limited. Here we establish an intrahepatic L1 reporter assay that enables immunohistochemical detection and quantitative analysis of L1 retrotransposition in vivo. Using autonomous and non-autonomous L1 reporter variants, we demonstrate clearly detectable somatic L1 activity in the mouse liver. Comparative analysis of L1 activity in liver tissue and tumor-derived cell culture reveals that tumor cells preferentially restrict L1 at early regulatory stages, consistent with epigenetic control, whereas downstream defence mechanisms are comparatively permissive. In contrast, normal liver tissue shows stronger restriction at later stages of the L1 life cycle. Together, our results provide direct experimental evidence for somatic L1 retrotransposition in vivo in adult liver and reveal distinct regulatory strategies that shape L1 activity in tumor versus normal somatic cells. TeaserGenome destabilizing L1 retrotransposon activity is present in somatic tissues, where it likely contributes to cancer development.

genetics↗

bioRxiv2023

The loss of DNA polymerase epsilon accessory subunits POLE3-POLE4 leads to BRCA1-independent PARP inhibitor sensitivity

The clinical success of PARP1/2 inhibitors prompts the expansion of their applicability beyond homologous recombination deficiency. Here, we demonstrate that the loss of the accessory subunits of DNA polymerase epsilon, POLE3 and POLE4, sensitizes cells to PARP inhibitors. We show that the sensitivity of POLE4 knockouts is not due to a compromised response to DNA damage or homologous recombination deficiency. Instead, POLE4 deletion generates replication stress with the accumulation of single-stranded DNA gaps upon PARP inhibitor treatment. In POLE4 knockouts, replication stress leads to elevated DNA-PK signaling revealing a role of POLE4 in regulating DNA-PK activation. Moreover, POLE4 knockouts show synergistic sensitivity to the co-inhibition of ATR and PARP. Finally, POLE4 loss enhances the sensitivity of BRCA1-deficient cells to PARP inhibitors and counteracts acquired resistance consecutive to restoration of homologous recombination. Altogether, our findings establish POLE4 as a promising target to improve PARP inhibitor driven therapies and hamper acquired PARP inhibitor resistance.

cell biology↗