Tdp1 protects from topoisomerase 1–mediated chromosomal breaks in adult zebrafish but is dispensable during larval development

Abstract

Deficiency in the DNA end-processing enzyme, tyrosyl-DNA phosphodiesterase 1 (TDP1), causes progressive neurodegeneration in humans. Here, we generated a tdp1 knockout zebrafish and confirmed the lack of TDP1 activity. In adulthood, homozygotes exhibit hypersensitivity to topoisomerase 1 (Top1) poisons and a very mild locomotion defect. Unexpectedly, embryonic tdp1−/− zebrafish were not hypersensitive to Top1 poisons and did not exhibit increased Top1-DNA breaks. This is in contrast to the hypersensitivity of Tdp1-deficient vertebrate models reported to date. Tdp1 is dispensable in the zebrafish embryo with transcript levels down-regulated in response to Top1-DNA damage. In contrast, apex2 and ercc4 (xpf) transcripts were up-regulated. These findings identify the tdp1−/− zebrafish embryo as the first vertebrate model that does not require Tdp1 to protect from Top1-DNA damage and identify apex2 and ercc4 (xpf) as putative players fulfilling this role. It highlights the requirement of distinct DNA repair factors across the life span of vertebrates.

Interplay between symmetric arginine dimethylation and ubiquitylation regulates TDP1 proteostasis for the repair of topoisomerase I-DNA adducts

“…Quantitative PCR analysis shows that, unlike the protein level, TDP1 mRNA levels were diminished in PRMT5 KO cells compared with that of wildtype cells (Figure 1D). CPT treatment did not increase but rather decreased the TDP1 mRNA levels as reported previously (Das et al, 2009;Zaksauskaite et al, 2021). This is consistent with PRMT5 KO cells, suggesting that the enhancement in TDP1 protein levels is due to modulations at the post-translational level (Figure 1D).…”

Myeloid cell‐specific topoisomerase 1 inhibition using DNA origami mitigates neuroinflammation

“…The intracellular/intranuclear regulation of TOP1 activity is not fully elucidated, but some proteins have been proposed to regulate the recruitment of TOP1 to chromatin or TOP1 degradation. Among these, BTB/POZ domain‐containing protein 1 (BTBD1) is known to specifically bind to TOP1 and may function as a TOP1 degradation regulator (Husain et al , 2016 ); the DNA end‐processing enzyme TDP1 counteracts the biological function of TOP1 cleavage complexes (Zaksauskaite et al , 2021 ); the serine/arginine‐rich splicing factor 1 (SRSF1) inhibits the recruitment of TOP1 from the nucleoplasm to the nucleolus (Girstun et al , 2019 ). We observed a concomitant decrease in the mRNA expression of these three negative regulators of TOP1 following microglial activation (Fig 2C ).…”

DNA damage as a mechanism of neurodegeneration in ALS and a contributor to astrocyte toxicity

“…As such, it is of importance to generate models to test putative molecules. For example, knockout of tdp1 in zebrafish identified apex2 and ercc4 as putative molecules which compensated for tdp1 loss [50]. Enforcing DNA repair has been shown to improve motor neuron survival following injury.…”