RNA/aTNA chimeras: RNAi effects and nucleases resistance of single and double stranded RNAs

A Wireframe DNA Cube: Antibody Conjugate for Targeted Delivery of Multiple Copies of Monomethyl Auristatin E

In recent years, several antibody drug conjugates (ADC) have been accepted by the FDA as therapeutics against cancer. It is well-known that control of drug-to-antibody ratio (DAR) is vital for the success of an ADC, which inspires the advancement of better and simpler methods for tight control of DAR. We present the development of an antibody DNA wireframe cube conjugate for precise control of DAR. The DNA wireframe cube consists of four single strands, which when folded present eight single stranded domains. One domain is bound to a monofunctionalized antibody DNA conjugate, and the seven others are attached to DNA functionalized with the potent tubulin inhibitor MMAE, thereby preparing an ADC with a DAR of precisely seven. The formation of the ADC is investigated by gel electrophoresis and atomic force microscopy. Lastly, the developed MMAE loaded ADC was used for targeted drug delivery in vitro.

Exploring PAZ/3'-overhang interaction to improve siRNA specificity. A combined experimental and modeling study

The understanding of the dynamical and mechanistic aspects that lie behind siRNA-based gene regulation is a requisite to boost the performance of siRNA therapeutics. A systematic experimental and computational study on the 3'-overhang structural requirements for the design of more specific and potent siRNA molecules was carried out using nucleotide analogues differing in structural parameters, such as sugar constraint, lack of nucleobase, distance between the phosphodiester backbone and nucleobase, enantioselectivity, and steric hindrance. The results established a set of rules governing the siRNA-mediated silencing, indicating that the thermodynamic stability of the 5'-end is a crucial determinant for antisense-mediated silencing but is not sufficient to avoid sense-mediated silencing. Both theoretical and experimental approaches consistently evidence the existence of a direct connection between the PAZ/3'-overhang binding affinity and siRNA's potency and specificity. An overall description of the systems is thus achieved by atomistic simulations and free energy calculations that allow us to propose a robust and self-contained procedure for studying the factors implied in PAZ/3'-overhang siRNA interactions. A higher RNAi activity is associated with a moderate-to-strong PAZ/3'-overhang binding. Contrarily, lower binding energies compromise siRNA potency, increase specificity, and favor siRNA downregulation by Ago2-independent mechanisms. This work provides in-depth details for the design of powerful and safe synthetic nucleotide analogues for substitution at the 3'-overhang, enabling some of the intrinsic siRNA disadvantages to be overcome.

The impact of an extended nucleobase-2′-deoxyribose linker in the biophysical and biological properties of oligonucleotides

The introduction of a novel thymine derivative at the 3′-end of the sense strand generates more potent and selective siRNAs.

Synthesis and biophysical properties of (L)-aTNA based G-quadruplexes

Novel G-quadruplex structures are constructed by acyclic (L)-threninol nucleic acid and their synthesis and biophysical properties are described. Pyrene excimer fluorescence and circular dichroism (CD) data revealed that four strands of aTNA are oriented in antiparallel direction.

siRNA and RNAi optimization

The discovery and examination of the posttranscriptional gene regulatory mechanism known as RNA interference (RNAi) contributed to the identification of small interfering RNA (siRNA) and the comprehension of its enormous potential for clinical purposes. Theoretically, the ability of specific target gene downregulation makes the RNAi pathway an appealing solution for several diseases. Despite numerous hurdles resulting from the inherent properties of siRNA molecule and proper delivery to the target tissue, more than 50 RNA-based drugs are currently under clinical testing. In this work, we analyze the recent literature in the optimization of siRNA molecules. In detail, we focused on describing the most recent advances of siRNA field aimed at optimize siRNA pharmacokinetic properties. Special attention has been given in describing the impact of RNA modifications in the potential off-target effects (OTEs) such as saturation of the RNAi machinery, passenger strand-mediated silencing, immunostimulation, and miRNA-like OTEs as well as to recent developments on the delivery issue. The novel delivery systems and modified siRNA provide significant steps toward the development of reliable siRNA molecules for therapeutic use. WIREs RNA 2016, 7:316-329. doi: 10.1002/wrna.1337 For further resources related to this article, please visit the WIREs website.

Modulation of the RNA Interference Activity Using Central Mismatched siRNAs and Acyclic Threoninol Nucleic Acids (aTNA) Units

The understanding of the mechanisms behind nucleotide recognition by Argonaute 2, core protein of the RNA-induced silencing complex, is a key aspect in the optimization of small interfering RNAs (siRNAs) activity. To date, great efforts have been focused on the modification of certain regions of siRNA, such as the 3'/5'-termini and the seed region. Only a few reports have described the roles of central positions flanking the cleavage site during the silence process. In this study, we investigate the potential correlations between the thermodynamic and silencing properties of siRNA molecules carrying, at internal positions, an acyclic L-threoninol nucleic acid (aTNA) modification. Depending on position, the silencing is weakened or impaired. Furthermore, we evaluate the contribution of mismatches facing either a natural nucleotide or an aTNA modification to the siRNA potency. The position 11 of the antisense strand is more permissive to mismatches and aTNA modification, in respect to the position 10. Additionally, comparing the ON-/OFF-target silencing of central mismatched siRNAs with 5'-terminal modified siRNA, we concluded: (i) central perturbation of duplex pairing features weights more on potency rather than silencing asymmetry; (ii) complete bias for the ON-target silencing can be achieved with single L-threoninol modification near the 5'-end of the sense strand.

Modulation of the stability of i-motif structures using an acyclic threoninol cytidine derivative

The effect of aTNA (acyclic threoninol nucleic acids) units on the stability of intramolecular i-motifs was investigated by spectroscopic techniques.