Efficient scar-free knock-ins of several kilobases in plants by engineered CRISPR-Cas endonucleases

In plants and mammals, non-homologous end-joining is the dominant pathway to repair DNA double-strand breaks, making it challenging to generate knock-in events. In this study, we identified two groups of exonucleases from the herpes virus and the bacteriophage T7 families that conferred an up to 38-fold increase in homology-directed repair frequencies when fused to Cas9/Cas12a in a tobacco mosaic virus-based transient assay in Nicotiana benthamiana. We achieved precise and scar-free insertion of several kilobases of DNA both in transient and stable transformation systems. In Arabidopsis thaliana, fusion of Cas9 to a herpes virus family exonuclease led to 10-fold higher frequencies of knock-ins in the first generation of transformants. In addition, we demonstrated stable and heritable knock-ins in wheat in 1% of the primary transformants. Taken together, our results open perspectives for the routine production of heritable knock-in and gene replacement events in plants.

Human uric acid transporter 1 (hURAT1): an inhibitor structure-activity relationship (SAR) study

The current study describes the chemical synthesis of a series of (2-ethylbenzofuran-3-yl)(substituted-phenyl)methanone compounds and their subsequent in vitro testing via oocytes expressing hURAT1. The experimental data support the notion that a potent hURAT1 inhibitor requires an anion (i.e., a formal negative charge) to interact with the positively charged hURAT1 binding pocket. An anion appears to be a primary requirement in order to be a hURAT1 substrate (i.e., urate) or inhibitor. We discuss the inhibitor structure-activity relationship and how electronically donating or withdrawing groups attached to the B-ring can decrease or increase inhibitory potency, respectively.