Scientists at Peking University unveiled a novel RNA codon expansion platform that enables precise incorporation of noncanonical amino acids into proteins in mammalian cells without interfering with natural translation termination. By introducing programmable pseudouridine modifications into messenger RNA, the technique converts standard codons into bioorthogonal variants, abolishing translation termination interference seen in prior methods that reassign stop codons. This advance offers refined control over genetic code manipulation, enhancing the scope of protein engineering for therapeutic and synthetic biology applications.