The SH integral membrane protein of the paramyxovirus simian virus 5 is required to block apoptosis in MDBK cells.
In some cell types the paramyxovirus simian virus 5 (SV5) causes little cytopathic effect (CPE) and infection continues productively for long periods of time; e.g., SV5 can be produced from MDBK cells for up to 40 days with little CPE. SV5 differs from most paramyxoviruses in that it encodes a small (44-amino-acid) hydrophobic integral membrane protein (SH). When MDBK cells were infected with a recombinant SV5 containing a deletion of the SH gene (rSV5DeltaSH), the MDBK cells exhibited an increase in CPE compared to cells infected with wild-type SV5 (recovered from cDNA; rSV5). The increased CPE correlated with an increase in apoptosis in rSV5DeltaSH-infected cells over mock-infected and rSV5-infected cells when assayed for annexin V binding, DNA content (propidium iodide staining), and DNA fragmentation (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling assay). In rSV5DeltaSH-infected MDBK cells an increase in caspase-2 and caspase-3 activities was observed. By using peptide inhibitors of individual caspases it was found that caspase-2 and caspase-3 were activated separately in rSV5DeltaSH-infected cells. Expression of caspase-2 and -3 in rSV5DeltaSH-infected MDBK cells appeared not to require STAT1 protein, as STAT1 protein could not be detected in SV5-infected MDBK cells. When mutant mice homologous for a targeted disruption of STAT1 were used as a model animal system and infected with the viruses it was found that rSV5DeltaSH caused less mortality than wild-type rSV5, consistent with the notion of clearance of apoptotic cells in a host species.
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Howard Hughes Medical Institute, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208-3500, USA.
Lin
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Durbin
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Durbin
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RK
Lamb
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D000818:Animals; D017209:Apoptosis; D053143:Caspase 2; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002417:Cattle; D002460:Cell Line; D003588:Cytopathogenic Effect, Viral; D004268:DNA-Binding Proteins / Q000378:metabolism; D004285:Dogs; D004789:Enzyme Activation; D000882:Haplorhini; D006367:HeLa Cells; D006801:Humans; D010252:Paramyxoviridae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D015682:Retroviridae Proteins, Oncogenic / Q000235:genetics / Q000378:metabolism*; D050794:STAT1 Transcription Factor; D015534:Trans-Activators / Q000378:metabolism
D004268:DNA-Binding Proteins; D015682:Retroviridae Proteins, Oncogenic; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D015534:Trans-Activators; C056150:small hydrophobic protein, virus; C505407:CASP3 protein, human; D053143:Caspase 2; D053148:Caspase 3; D020169:Caspases