Barazandeh, M. | bioRxiv Science

bioRxiv2025

Friend and Foe: Genome-Wide Analysis of the Tardigrade Dsup Protein Expressed in Yeast Reveals Trade-offs of DNA Protection

Tardigrades are among the most resilient eukaryotes known, capable of surviving a wide range of extreme conditions. While their genomes contain thousands of tardigrade-specific genes, one key contributor to their stress resistance is the Damage suppressor (Dsup) protein. Previous work showed that expression of Dsup in cancer cells reduced DNA damage caused by X-rays. This observation has sparked growing interest in Dsup across diverse model organisms. Most studies to date have focused on phenotypic outcomes, while the mechanisms and consequences of Dsup remain poorly understood. Deciphering its mechanism is crucial, especially because Dsup expression is deleterious to some cells and organisms. In this work, we show that Dsup protects yeast against a variety of DNA-damaging agents. However, this protection is not universal, and it has a fitness cost. Analysis of nucleosome occupancy of cells expressing Dsup shows that effects on chromatin are modest, without global remodeling, and transcriptome analysis reveals a robust induction of oxidative stress pathways, which might be a form of preconditioning for oxidative stress. Genome-wide screens of [~]4300 loss-of-function mutants expressing Dsup shows that deletions incompatible with Dsup are highly enriched for DNA repair processes and that under DNA damage stress, Dsup can protect some mutants in a pathway-specific manner. Our findings demonstrate that while Dsup broadly enhances resistance to genotoxic stress, it also imposes physiological costs and generates new dependencies on DNA repair and genome maintenance pathways.

genomics↗

bioRxiv2024

Extensive binding of uncharacterized human transcription factors to genomic dark matter

The functional impact of a large portion of the human genome known as "dark matter DNA", which is composed mainly of repeat sequences, remains enigmatic. The genome also encodes hundreds of putative and poorly characterized transcription factors (TFs). Here, we determined genomic binding locations of 166 poorly characterized human TFs in living cells. Nearly half of them associate strongly with known regulatory regions such as promoters and enhancers, frequently co-localizing with each other at conserved motif matches. The other half often associate with genomic dark matter, however, at largely non-overlapping (i.e., unique) sites, via intrinsic sequence recognition. Fifty-four of the latter half, which we term "Dark TFs", mainly bind within regions of closed chromatin, with each recognizing a unique set of repeat sequences. The Dark TFs include many KZNFs, which are known to bind and silence TEs, and other TFs with apparent repressive functions. By contrast, some may be pioneers: we find that induction of TPRX1, a known regulator of zygotic preimplantation, leads to chromatin opening at many of its binding sites in the dark matter genome. Altogether, our results shed light on a large fraction of poorly characterized human TFs and simultaneously illuminate the diversity of function within the dark matter genome.

genomics↗