Thermostable Protein Engineering In article number 2404680, Trung Thanh Thach, Jaekyung Hyun Yong Ho Kim, and co-workers introduce a structure-guided engineered SaCas9 variant with enhanced thermostability and compactness, enabling efficient gene suppression through nonviral delivery. The engineered sdCas9-KRAB-R system demonstrates superior nuclear localization and in vivo knockdown efficiency, showcasing its potential as a robust tool for CRISPR interference and targeted genomic regulation.