Tan, M. H. | Search bioRxiv

bioRxiv2020

A CRISPR-based SARS-CoV-2 diagnostic assay that is robust against viral evolution and RNA editing

Extensive testing is essential to break the transmission of the new coronavirus SARS-CoV-2, which causes the ongoing COVID-19 pandemic. Recently, CRISPR-based diagnostics have emerged as attractive alternatives to quantitative real-time PCR due to their faster turnaround time and their potential to be used in point-of-care testing scenarios. However, existing CRISPR-based assays for COVID-19 have not considered viral genome mutations and RNA editing in human cells. Here, we present the VaNGuard (Variant Nucleotide Guard) test that is not only specific and sensitive for SARS-CoV-2, but can also detect the virus when its genome or transcriptome has evolved or has been edited by deaminases in infected human cells. We show that an engineered AsCas12a enzyme is more tolerant of mismatches than wildtype LbCas12a and that multiplexed Cas12a targeting can overcome the presence of single nucleotide variations. Our assay can be completed in 30 minutes with a dipstick for a rapid point-of-care test.Competing Interest StatementThe authors have declared no competing interest.View Full Text

genomics↗

bioRxiv2020

Direct RNA sequencing reveals structural differences between transcript isoforms

The ability to correctly assign structure information to an individual transcript in a continuous and phased manner is critical to understanding RNA function. RNA structure play important roles in every step of an RNAs lifecycle, however current short-read high throughput RNA structure mapping strategies are long, complex and cannot assign unique structures to individual gene-linked isoforms in shared sequences. To address these limitations, we present an approach that combines structure probing with SHAPE-like compound NAI-N3, nanopore direct RNA sequencing, and one-class support vector machines to detect secondary structures on near full-length RNAs (PORE-cupine). PORE-cupine provides rapid, direct, accurate and robust structure information along known RNAs and recapitulates global structural features in human embryonic stem cells. The majority of gene-linked isoforms showed structural differences in shared sequences both local and distal to the alternative splice site, highlighting the importance of long-read sequencing for phasing of structures. Structural differences between gene-linked isoforms are associated with differential translation efficiencies globally, highlighting the role of structure as a pervasive mechanism for regulating isoform-specific gene expression inside cells.

biochemistry↗