Expression of an equine herpesvirus 1 ICP22/ICP27 hybrid protein encoded by defective interfering particles associated with persistent infection.
Defective interfering (DI) particles of equine herpesvirus type 1 (EHV-1) are capable of mediating persistent infection (S. A. Dauenhauer, R. A. Robinson, and D. J. O'Callaghan, J. Gen. Virol. 60:1-14, 1982; R. A. Robinson, R. B. Vance, and D. J. O'Callaghan, J. Virol. 36:204-219, 1980). Sequence analysis of cloned DI particle DNA revealed that portions of two regulatory genes, ICP22 (IR4) and ICP27 (UL3), are linked in frame to form a unique hybrid open reading frame (ORF). This hybrid ORF, designated as the IR4/UL3 gene, encodes the amino-terminal 196 amino acids of the IR4 protein (ICP22 homolog) and the carboxy-terminal 68 amino acids of the UL3 protein (ICP27 homolog). Portions of DNA sequences encoding these two regulatory proteins, separated by more than 115 kbp in the standard virus genome, were linked presumably by a homologous recombination event between two identical 8-bp sequences. Reverse transcriptase-PCR and S1 nuclease analyses revealed that this unique ORF is transcribed by utilizing the transcription initiation site of ICP22 and the polyadenylation signal of ICP27 in DI particle-enriched infection. Immunoprecipitation and Western blot (immunoblot) analyses with antisera to the ICP22 and ICP27 proteins demonstrated that a 31-kDa hybrid protein was synthesized in the DI particle-enriched infection but not in standard virus infection. This 31-kDa hybrid protein was expressed at the same time as the ICP22 protein in DI particle-enriched infection and migrated at the same location on polyacrylamide gel electrophoresis as the protein expressed from a cloned IR4/UL3 expression vector. These observations suggested that the unique IR4/UL3 hybrid gene is expressed from the DI particle genome and may play a role in DI particle-mediated persistent infection.
Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130-3932, USA.
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M
Chen
R N
RN
Harty
Y
Y
Zhao
V R
VR
Holden
D J
DJ
O'Callaghan
D000595:Amino Acid Sequence; D000818:Animals; D000914:Antibodies, Viral / Q000276:immunology; D001483:Base Sequence; D015153:Blotting, Western; D002460:Cell Line; D017931:DNA Primers; D004279:DNA, Viral; D003673:Defective Viruses / Q000235:genetics / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D016679:Genome, Viral; D004861:Herpesvirus 1, Equid / Q000235:genetics / Q000378:metabolism*; D017874:Immediate-Early Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D012367:RNA, Viral / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000276:immunology; D015719:Single-Strand Specific DNA and RNA Endonucleases / Q000378:metabolism; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D054334:Viral Regulatory and Accessory Proteins
D000914:Antibodies, Viral; D017931:DNA Primers; D004279:DNA, Viral; C057294:ICP22 protein, human herpesvirus 1; D017874:Immediate-Early Proteins; D012333:RNA, Messenger; D012367:RNA, Viral; D011993:Recombinant Fusion Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C076116:UL3 protein, Equine herpesvirus 1; C078424:EUS1 protein, Equine herpesvirus 1; D015719:Single-Strand Specific DNA and RNA Endonucleases