Z-DNA formation in promoters conserved between human and mouse are associated with increased transcription reinitiation rates

A long-standing question concerns the role of Z-DNA in transcription. Here we use a deep learning approach DeepZ that predicts Z-flipons based on DNA sequence, structural properties of nucleotides and omics data. We examined Z-flipons that are conserved between human and mouse genomes after generating whole-genome Z-flipon maps and then validated them by orthogonal approaches based on high resolution chemical mapping of Z-DNA and the transformer algorithm Z-DNABERT. For human and mouse, we revealed similar pattern of transcription factors, chromatin remodelers, and histone marks associated with conserved Z-flipons. We found significant enrichment of Z-flipons in alternative and bidirectional promoters associated with neurogenesis genes. We show that conserved Z-flipons are associated with increased experimentally determined transcription reinitiation rates compared to promoters without Z-flipons, but without affecting elongation or pausing. Our findings support a model where Z-flipons engage Transcription Factor E and impact phenotype by enabling the reset of preinitiation complexes when active, and the suppression of gene expression when engaged by repressive chromatin complexes.

The anti-cancer drug candidate CBL0137 induced necroptosis via forming left-handed Z-DNA and its binding protein ZBP1 in liver cells

CBL0137, a promising small molecular anti-cancer drug candidate, has been found to effectively induce apoptosis via activating p53 and suppressing nuclear factor-kappa B (NF-κB). However, it is still not clear whether CBL0137 can induce necroptosis in liver cancer; and if so, what is the underlying molecular mechanism. Here we found that CBL0137 could significantly induce left-handed double helix structure Z-DNA formation in HepG2 cells as shown by Z-DNA specific antibody assay, which was further confirmed by observing the expression of Z-DNA binding protein 1 (ZBP1) and adenosine deaminase acting on RNA 1 (ADAR1). Interestingly, we found that caspase inhibition significantly promoted CBL0137-induced necroptosis, which was further supported with the increase of the late apoptosis and necrosis assessed by the flow cytometry. Furthermore, we found that CBL0137 can also induce the expression of the three necroptosis-related proteins: receptor interacting serine/threonine kinase 1 (RIPK1), receptor interacting serine/threonine kinase 3 (RIPK3), and mixed lineage kinase domain-like (MLKL). Taken together, it was assumed that CBL0137-indued necroptosis in liver cells was due to induction of Z-DNA and ZBP1, which activated RIPK1/RIPK3/MLKL pathway. This represents the first report on the induction of the Z-DNA-mediated necroptosis by CBL0137 in the liver cancer cells, which should provide new perspectives for CBL0137 treatment of liver cancer.

Experimental detection of conformational transitions between forms of DNA: problems and prospects

Under different conditions, the DNA double helix can take different geometric forms. Of the large number of its conformations, in addition to the "canonical" B form, the A, C, and Z forms are widely known, and the D, Hoogsteen, and X forms are less known. DNA locally takes the A, C, and Z forms in the cell, in complexes with proteins. We compare different methods for detecting non-canonical DNA conformations: X-ray, IR, and Raman spectroscopy, linear and circular dichroism in both the infrared and ultraviolet regions, as well as NMR (measurement of chemical shifts and their anisotropy, scalar and residual dipolar couplings and inter-proton distances from NOESY (nuclear Overhauser effect spectroscopy) data). We discuss the difficulties in applying these methods, the problems of theoretical interpretation of the experimental results, and the prospects for reliable identification of non-canonical DNA conformations.

Metal Complexes as DNA Synthesis and/or Repair Inhibitors: Anticancer and Antimicrobial Agents

Medicinal inorganic chemistry involving the utilization of metal-based compounds as therapeutics has become a field showing distinct promise. DNA and RNA are ideal drug targets for therapeutic intervention in the case of various diseases, such as cancer and microbial infection. Metals play a vital role in medicine, with at least 10 metals known to be essential for human life and a further 46 nonessential metals having been involved in drug therapies and diagnosis. These metal-based complexes interact with DNA in various ways, and are often delivered as prodrugs which undergo activation in vivo. Metal complexes cause DNA crosslinking, leading to the inhibition of DNA synthesis and repair. In this review, the various interactions of metal complexes with DNA nucleic acids, as well as the underlying mechanism of action, were highlighted. Furthermore, we also discussed various tools used to investigate the interaction between metal complexes and the DNA. The tools included in vitro techniques such as spectroscopy and electrophoresis, and in silico studies such as protein docking and density-functional theory that are highlighted for preclinical development.

Z-form extracellular DNA is a structural component of the bacterial biofilm matrix

Biofilms are community architectures adopted by bacteria inclusive of a self-formed extracellular matrix that protects resident bacteria from diverse environmental stresses and, in many species, incorporates extracellular DNA (eDNA) and DNABII proteins for structural integrity throughout biofilm development. Here, we present evidence that this eDNA-based architecture relies on the rare Z-form. Z-form DNA accumulates as biofilms mature and, through stabilization by the DNABII proteins, confers structural integrity to the biofilm matrix. Indeed, substances known to drive B-DNA into Z-DNA promoted biofilm formation whereas those that drive Z-DNA into B-DNA disrupted extant biofilms. Importantly, we demonstrated that the universal bacterial DNABII family of proteins stabilizes both bacterial- and host-eDNA in the Z-form in situ. A model is proposed that incorporates the role of Z-DNA in biofilm pathogenesis, innate immune response, and immune evasion.