Discovery of an RNA virus 3'->5' exoribonuclease that is critically involved in coronavirus RNA synthesis.

Replication of the giant RNA genome of severe acute respiratory syndrome (SARS) coronavirus (CoV) and synthesis of as many as eight subgenomic (sg) mRNAs are mediated by a viral replicase-transcriptase of outstanding complexity that includes an essential endoribonuclease activity. Here, we show that the CoV replicative machinery, unlike that of other RNA viruses, also uses an exoribonuclease (ExoN) activity, which is associated with nonstructural protein (nsp) 14. Bacterially expressed forms of SARS-CoV nsp14 were shown to act on both ssRNAs and dsRNAs in a 3'-->5' direction.

Major genetic marker of nidoviruses encodes a replicative endoribonuclease.

Coronaviruses are important pathogens that cause acute respiratory diseases in humans. Replication of the approximately 30-kb positive-strand RNA genome of coronaviruses and discontinuous synthesis of an extensive set of subgenome-length RNAs (transcription) are mediated by the replicase-transcriptase, a barely characterized protein complex that comprises several cellular proteins and up to 16 viral subunits. The coronavirus replicase-transcriptase was recently predicted to contain RNA-processing enzymes that are extremely rare or absent in other RNA viruses.

Rapid identification of coronavirus replicase inhibitors using a selectable replicon RNA.

A previously unknown coronavirus (CoV) is the aetiological agent causing severe acute respiratory syndrome (SARS), for which an effective antiviral treatment is urgently needed. To enable the rapid and biosafe identification of coronavirus replicase inhibitors, we have generated a non-cytopathic, selectable replicon RNA (based on human CoV 229E) that can be stably maintained in eukaryotic cells. Most importantly, the replicon RNA mediates reporter gene expression as a marker for coronavirus replication.

Mechanisms and enzymes involved in SARS coronavirus genome expression.

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.

Antibodies present in normal human serum inhibit invasion of human brain microvascular endothelial cells by Listeria monocytogenes.

Listeria monocytogenes causes meningitis and encephalitis in humans and crosses the blood-brain barrier by yet unknown mechanisms. The interaction of the bacteria with different types of endothelial cells was recently analyzed, and it was shown that invasion into, but not adhesion to, human brain microvascular endothelial cells (HBMEC) depends on the product of the inlB gene, the surface molecule InlB, which is a member of the internalin multigene family. In the present study we analyzed the role of the medium composition in the interaction of L.