Biology subjects

Houbron, E.

Publications and source records attributed to Houbron, E..

3 recordsLinked to original sources

bioRxiv2022

Evaluation of microRNA variant maturation prior to genome edition

* AbstractAssessment of the functionality of individual microRNA/target sites is a crucial issue. Genome editing techniques should theoretically permit a fine functional exploration of such interactions, allowing the mutation of microRNAs or individual binding sites in a complete in vivo setting, therefore abrogating or restoring individual interactions on demand. A major limitation to this experimental strategy is the influence of microRNA sequence on its accumulation level, which introduces a confounding effect when assessing phenotypic rescue by compensatorily mutated microRNA and target site. Here we describe a simple assay to identify microRNA variants most likely to accumulate at wild-type levels even though their sequence has been mutated. In this assay, quantification of a reporter construct in cultured cells predicts the efficiency of an early biogenesis step, the Drosha-dependent cleavage of microRNA precursors, which appears to be a major determinant of microRNA accumulation in our variant collection. This system allowed the generation of a mutant Drosophila strain expressing a bantam microRNA variant at wild-type levels.

molecular biology↗

bioRxiv2022

Biochemistry-informed design selects potent siRNAs against SARS-CoV-2

RNA interference (RNAi) offers an efficient way to repress genes of interest, and it is widely used in research settings. Clinical applications emerged more recently, with 5 approved siRNAs (the RNA guides of the RNAi effector complex) against human diseases. The development of siRNAs against the SARS-CoV-2 virus could therefore provide the basis of novel COVID-19 treatments, while being easily adaptable to future variants or to other, unrelated viruses. Because the biochemistry of RNAi is very precisely described, it is now possible to design siRNAs with high predicted activity and specificity using only computational tools. While previous siRNA design algorithms tended to rely on simplistic strategies (raising fully complementary siRNAs against targets of interest), our approach uses the most up-to-date mechanistic description of RNAi to allow mismatches at tolerable positions and to force them at beneficial positions, while optimizing siRNA duplex asymmetry. Our pipeline proposes 8 siRNAs against SARS-CoV-2, and ex vivo assessment confirms the high antiviral activity of 6 out of 8 siRNAs, also achieving excellent variant coverage (with several 3-siRNA combinations recognizing each correctly-sequenced variant as of September 2022). Our approach is easily generalizable to other viruses as long as a variant genome database is available. With siRNA delivery procedures being currently improved, RNAi could therefore become an efficient and versatile antiviral therapeutic strategy.

molecular biology↗

bioRxiv2021

miR-34a is not a candidate tumor suppressor

While several microRNAs (miRNAs) have been proposed to act as tumor suppressors, a consensual definition of tumor suppressing miRNAs is still missing. Similarly to coding genes, we propose that tumor suppressor miRNAs must show evidence of genetic or epigenetic inactivation in cancers, and exhibit an anti-tumorigenic (e.g., anti-proliferative) activity under endogenous expression levels. Here we observe that this definition excludes the most extensively studied tumor suppressor candidate miRNA, miR-34a. In analyzable cancer types, miR-34a does not appear to be down-regulated in primary tumors relatively to normal adjacent tissues. Deletion of miR-34a is occasionally found in human cancers, but it does not seem to be driven by an anti-tumorigenic activity of the miRNA, since it is not observed upon smaller, miR-34a-specific alterations. Its anti-proliferative action was observed upon large, supra-physiological transfection of synthetic miR-34a in cultured cells, and our data indicates that endogenous miR-34a levels do not have such an effect. Our results therefore argue against a general tumor suppressive function for miR-34a, providing an explanation to the lack of efficiency of synthetic miR-34a administration against solid tumors.

genetics↗