Expression of the Replicase–Transcriptase Complex

Abstract

The replicase–transcriptase complex (RTC) is a key component of the coronavirus replication cycle, responsible for viral genome replication and subgenomic RNA synthesis. Following the release of the viral nucleocapsid into the host cell cytoplasm, the replicase gene encoded within the viral genomic RNA is translated. Coronavirus replicase expression involves a unique ribosomal frameshifting mechanism that allows the production of large polyproteins, which are subsequently processed into multiple nonstructural proteins (nsps). These proteins assemble into the RTC and perform essential enzymatic and regulatory functions required for viral replication, transcription, and immune evasion. This article discusses the molecular mechanisms underlying RTC expression, the functions of major nonstructural proteins, and their significance in coronavirus biology and pathogenesis.