Mechanisms and enzymes involved in SARS coronavirus genome expression

1 Institute of Virology and Immunology, University of Würzburg, Versbacher Str. 7, 97078 Würzburg, Germany 2 Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands 3 Institute for Medical Virology, Johann Wolfgang Goethe University, Frankfurt (Main), Germany Correspondence John Ziebuhr j.ziebuhr{at}mail.uni-wuerzburg.de A novel coronavirus is the causative agent of the current epidemic of severe acute respiratory syndrome (SARS). Coronaviruses are exceptionally large RNA viruses and employ complex regulatory mechanisms to express their genomes. Here, we determined the sequence of SARS coronavirus (SARS-CoV), isolate Frankfurt 1, and characterized key RNA elements and protein functions involved in viral genome expression. Important regulatory mechanisms, such as the (discontinuous) synthesis of eight subgenomic mRNAs, ribosomal frameshifting and post-translational proteolytic processing, were addressed. Activities of three SARS coronavirus enzymes, the helicase and two cysteine proteinases, which are known to be critically involved in replication, transcription and/or post-translational polyprotein processing, were characterized. The availability of recombinant forms of key replicative enzymes of SARS coronavirus should pave the way for high-throughput screening approaches to identify candidate inhibitors in compound libraries. Present address: Research Department, Cantonal Hospital, St Gallen, Switzerland. Published ahead of print on 19 June 2003 as DOI 10.1099/vir.0.19424-0. The nucleotide sequence of SARS-CoV, isolate Frankfurt 1, has been deposited in GenBank, accession no. AY291315 .