Efficient target cleavage by Type V Cas12a effectors programmed with split CRISPR RNA

CRISPR RNAs (crRNAs) that direct target DNA cleavage by Type V Cas12a nucleases consist of constant repeat-derived 5′-scaffold moiety and variable 3′-spacer moieties. Here, we demonstrate that removal of most of the 20-nucleotide scaffold has only a slight effect on in vitro target DNA cleavage by a Cas12a ortholog from Acidaminococcus sp. (AsCas12a). In fact, residual cleavage was observed even in the presence of a 20-nucleotide crRNA spacer moiety only. crRNAs split into separate scaffold and spacer RNAs catalyzed highly specific and efficient cleavage of target DNA by AsCas12a in vitro and in lysates of human cells. In addition to dsDNA target cleavage, AsCas12a programmed with split crRNAs also catalyzed specific ssDNA target cleavage and non-specific ssDNA degradation (collateral activity). V-A effector nucleases from Francisella novicida (FnCas12a) and Lachnospiraceae bacterium (LbCas12a) were also functional with split crRNAs. Thus, the ability of V-A effectors to use split crRNAs appears to be a general property. Though higher concentrations of split crRNA components are needed to achieve efficient target cleavage, split crRNAs open new lines of inquiry into the mechanisms of target recognition and cleavage and may stimulate further development of single-tube multiplex and/or parallel diagnostic tests based on Cas12a nucleases.     

Suppression of Ehrlich carcinoma growth by cobra venom factor

Cobra venom factor (CVF) depletes the complement system of the blood by forming stable convertase C3/C5 of the alternative pathway. We found that CVF from the Thailand cobra venom slows down the growth of subcutaneous Ehrlich carcinoma (EC) in mice at a dose of 1.7 nmol/g. Previously, we described a similar effect for the nerve growth factor (NGF) from the venom of this cobra. However, these factors did not exhibit either synergy or additive effect. On the contrary, they neutralized the antitumor effect of each other when they were administered simultaneously. Therefore, on the one hand, the NGF antitumor effect against EC manifests itself under the conditions of inflammation, and normal functioning of the complement system is necessary for this effect to occur. On the other hand, suppression of the humoral immune system leads to a slowdown of the EC growth, but administration of NGF prevents this.     

5-(Perylen-3-ylethynyl)uracil Derivatives Inhibit Reproduction of Respiratory Viruses

Russian Journal of Bioorganic Chemistry - In this work, we describe the synthesis of 5-(perylen-3-ylethynyl)uridine and its ability to effectively inhibit the replication of respiratory disease...