Regina Shebanova, Natalia Nikitchina, Nikita Shebanov, Konstantin Severinov and Ilya Mazunin from Skoltech have co-authored a paper “Efficient target cleavage by Type V Cas12a effectors programmed with split CRISPR RNA” that has been recently published in Nucleic Acids Research journal. The work is focused on the effector protein of CRISPR-Cas type V effector protein Cas12 from bacteria Acidaminococcus sp. The authors of the paper 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). 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. Based on studies of Cas12a orthologs from other bacteria the researchers claim that the ability of V-A effectors to use split crRNAs appears to be a general property. Moreover, 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. Full text of the paper is available here.