Programmable modulation of ribosomal frameshifting by mRNA targeting CRISPR-Cas12a system.

Minus 1 programmed ribosomal frameshifting (-1 PRF) is a conserved translational regulation event essential for critical biological processes, including the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) replication. Efficient trans-modulation of the structured RNA element crucial to -1 PRF will endow the therapeutic application. Here, we demonstrate that CRISPR RNA can stimulate efficient -1 PRF. Assembled CRISPR-Cas12a, but not CRISPR-Cas9, complex further enhances -1 PRF efficiency through its higher capacity to stall translating ribosomes. We additionally perform CRISPR-Cas12a targeting to impair the SARS-CoV-2 frameshifting pseudoknot structure via a focused screening. We demonstrate that targeting CRISPR-Cas12a results in more than 70% suppression of -1 PRF in vitro and about 50% suppression in mammalian cells. Our results show the expanded function of the CRISPR-Cas12 system in modulating -1 PRF efficiency through stalling ribosomes and deforming frameshifting stimulatory signals, which could serve as a new strategy for future coronavirus pandemics.

Photochemical reactivity of aqueous fullerene clusters: C60 versus C70.

Over the past few years, there has been a strong interest in exploring the potential impact of fullerenes in the environment. Despite that both C60 and C70 have been detected in environmental matrices, the research on the impact of higher fullerenes, such as C70, has been largely missing. This study evaluated and compared the phototransformation of aqueous C60 and C70 clusters (nC60 and nC70) and their 1O2 production under sunlight and lamp light irradiation (315nm, 360nm and 420nm). The nC60 and nC70 samples formed by direct mixing with water adopted a face-centered cubic (FCC) crystal structure. The apparent quantum yields (AQYs) of fullerene phototransformed were relatively constant over the examined wavelengths, while 1O2 production AQYs decreased with increased wavelengths. The long-term fate studies with outdoor sunlight indicated that both nC60 and nC70 lost considerable organic carbon contents (>80%) in water after ∼8 months of irradiation and that the intermediate photoproducts of nC60 and nC70 exhibited a progressively increased level of oxygen-containing functionalities. Overall, the study indicates that nC70 can be photochemically removed under sunlight conditions and that the photoreactivity of nC60 based on AQYs is greater than that of nC70.