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Holden VR, Caughman GB, Zhao Y, Harty RN, O'Callaghan DJ. Identification and characterization of the ICP22 protein of equine herpesvirus 1. J Virol 1994; 68:4329-40. [PMID: 8207808 PMCID: PMC236356 DOI: 10.1128/jvi.68.7.4329-4340.1994] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The equine herpesvirus 1 (EHV-1) homolog of herpes simplex virus type 1 ICP22 is differently expressed from the fourth open reading frame of the inverted repeat (IR4) as a 1.4-kb early mRNA and a 1.7-kb late mRNA which are 3' coterminal (V. R. Holden, R. R. Yalamanchili, R. N. Harty, and D. J. O'Callaghan, J. Virol. 66:664-673, 1992). To extend the characterization of IR4 at the protein level, the synthesis and intracellular localization of the IR4 protein were investigated. Antiserum raised against either a synthetic peptide corresponding to amino acids 270 to 286 or against a TrpE-IR4 fusion protein (IR4 residues 13 to 150) was used to identify the IR4 protein. Western immunoblot analysis revealed that IR4 is expressed abundantly from an open reading frame composed of 293 codons as a family of proteins that migrate between 42 to 47 kDa. The intracellular localization of IR4 was examined by cell fractionation, indirect immunofluorescence, and laser-scanning confocal microscopy. These studies revealed that IR4 is localized predominantly in the nucleus and is dispersed uniformly throughout the nucleus. Interestingly, when IR4 is expressed transiently in COS-1 or LTK- cells, a punctate staining pattern within the nucleus is observed by indirect immunofluorescence. Cells transfected with an IR4 mutant construct that encodes a C-terminal truncated (19 amino acids) IR4 protein exhibited greatly reduced intranuclear accumulation of the IR4 protein, indicating that this domain possesses an important intranuclear localization signal. Western blot analysis of EHV-1 virion proteins revealed that IR4 proteins are structural components of the virions. Surprisingly, the 42-kDa species, which is the least abundant and the least modified form of the IR4 protein family in infected cell extracts, was the most abundant IR4 protein present in purified virions.
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Affiliation(s)
- V R Holden
- Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130-3932
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Harty RN, Caughman GB, Holden VR, O'Callaghan DJ. Characterization of the myristylated polypeptide encoded by the UL1 gene that is conserved in the genome of defective interfering particles of equine herpesvirus 1. J Virol 1993; 67:4122-32. [PMID: 8389920 PMCID: PMC237781 DOI: 10.1128/jvi.67.7.4122-4132.1993] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Equine herpesvirus 1 (EHV-1, Kentucky A strain) preparations enriched for defective interfering particles (DIPs) can readily establish persistent infection. The UL1 gene, which is conserved in the genome of DIPs that mediate persistent infection, maps between nucleotides 1418 and 2192 (258 amino acids) from the L (long) terminus. UL1 has no homology with any known gene encoded by herpes simplex virus type 1 but has limited homology to open reading frame 2 of varicella-zoster virus and the "circ" gene of bovine herpesvirus type 1. Previous work showed that the EHV-1 UL1 gene belongs to the early kinetic class and is transcribed as a 1.2-kb polyadenylated mRNA (R. N. Harty, R. R. Yalamanchili, and D. J. O'Callaghan, Virology 183:830-833, 1991). In this report, the UL1 protein was identified and characterized as a 33-kDa polypeptide in EHV-1-infected cells by using rabbit polyclonal antiserum raised against a TrpE-UL1 fusion protein (amino acids 7 to 258 of UL1) synthesized in Escherichia coli. Results from Western blot (immunoblot), immunoprecipitation, indirect immunofluorescence, and biochemical analyses indicated that the UL1 polypeptide (i) is more abundant in cells infected with DIP-enriched virus than in cells infected with standard EHV-1, (ii) is synthesized as early as 3 h postinfection (p.i.) in infection with standard virus or in infection with DIP-enriched virus preparations and increases in abundance up to 12 h p.i., (iii) appears to be associated with the rough endoplasmic reticulum-Golgi apparatus early in infection (3 to 4 h p.i.), while a diffuse cytoplasmic pattern of fluorescence is observed late in infection (7 to 8 h p.i.), (iv) is modified by myristic acid as it contains a consensus N-terminal myristylation site and is readily labeled with [3H]myristic acid, and (v) is associated with mature EHV-1 virions.
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Affiliation(s)
- R N Harty
- Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130-3932
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Harty RN, Holden VR, O'Callaghan DJ. Transcriptional and translational analyses of the UL2 gene of equine herpesvirus 1: a homolog of UL55 of herpes simplex virus type 1 that is maintained in the genome of defective interfering particles. J Virol 1993; 67:2255-65. [PMID: 8383240 PMCID: PMC240359 DOI: 10.1128/jvi.67.4.2255-2265.1993] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Defective interfering particles (DIPs) of equine herpesvirus 1 (EHV-1; Kentucky A strain) mediate persistent infection. DNA sequences at the L terminus, which contain the UL2 gene (homolog of UL55 of herpes simplex virus type 1 and open reading frame 3 of varicella-zoster virus) of standard EHV-1, have been shown to be highly conserved in all clones of the EHV-1 DIP genome. The UL2 mRNA was characterized by S1 nuclease analyses, which mapped the 5' and 3' termini of the 0.9-kb early UL2 mRNA to approximately 26 and 16 nucleotides downstream of a TTTAAA box and polyadenylation signal, respectively. The UL2 open reading frame, present within both the EHV-1 standard and DIP genomes, was inserted into the transcription expression vector pGEM-3Z to yield constructs pGEML2 and pDIL2, respectively. After in vitro transcription and translation, both constructs yielded a comigrating 23-kDa protein, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Polyclonal antiserum was raised against the UL2 protein by injecting rabbits with a TrpE/UL2 fusion protein expressed from plasmid pATH23L2 in Escherichia coli. The UL2-specific antiserum reacted in Western immunoblot and immunoprecipitation analyses with a 23-kDa polypeptide synthesized in cells infected with standard EHV-1 or DIP-enriched virus. These data also indicated that the UL2 polypeptide was more abundant in DIP-infected cells than in standard EHV-1-infected cells. Results from time course and pulse-chase analyses suggested that the UL2 polypeptide has a rapid turnover rate in DIP-infected cells.
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Affiliation(s)
- R N Harty
- Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130-3932
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Smith RH, Zhao Y, O'Callaghan DJ. The equine herpesvirus 1 (EHV-1) UL3 gene, an ICP27 homolog, is necessary for full activation of gene expression directed by an EHV-1 late promoter. J Virol 1993; 67:1105-9. [PMID: 8380457 PMCID: PMC237469 DOI: 10.1128/jvi.67.2.1105-1109.1993] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
We have previously reported that the equine herpesvirus 1 (EHV-1) XbaI G restriction fragment (nucleotides 1436 to 7943 relative to the left terminus of the EHV-1 genome [Kentucky A strain]) is required in combination with the EHV-1 immediate-early (IE) gene to achieve significant activation of two representative EHV-1 late promoter-chloramphenicol acetyltransferase (CAT) recombinants in transient expression assays. In this report, we demonstrate that the XbaI G-encoded UL3 gene (an ICP27 homolog) provides a trans-acting factor which acts (in combination with the EHV-1 IE gene product) to increase reporter gene expression directed by an EHV-1 late promoter-CAT recombinant plasmid. We show that cloned copies of UL3 can successfully substitute for the XbaI G fragment in CAT assays and that stop codon insertion within the UL3 open reading frame inhibits the ability of UL3 to activate reporter gene expression in trans.
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Affiliation(s)
- R H Smith
- Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130-3932
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Breeden CA, Yalamanchili RR, Colle CF, O'Callaghan DJ. Identification and transcriptional mapping of genes encoded at the IR/Us junction of equine herpesvirus type 1. Virology 1992; 191:649-60. [PMID: 1333117 DOI: 10.1016/0042-6822(92)90240-p] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Two open reading frames (ORFs) encoded at the inverted repeat unique short (Us) junction of the Short (S) region of the equine herpesvirus type 1 genome were identified by DNA sequencing of a 2876 base pair (bp) genomic segment, and transcripts encoding these ORFs were characterized by Northern blot, S1 nuclease, and primer extension analyses. These studies also established the size of each inverted repeat to be 12,768 nucleotides (nts). The IR6 ORF (816 bp), mapping at nts 12,317-11,502 of the S region, is the last gene completely encoded within each inverted repeat and encodes a predicted 30.1-kDa protein of 272 amino acids, which does not exhibit homology to other alphaherpesvirus proteins. IR6 is expressed as an early transcript of 1.2 kb which is detected initially at 1.5 hr p.i. and up to 12 hr p.i. The transcription initiation and termination sites of IR6 were mapped by primer extension and S1 nuclease analyses to nts 12,465 and 11,408, respectively. The first ORF encoded within the Us segment (909 bp; EUS1), mapping at nts 13,397-12,489, encodes a predicted 33.5-kDa protein of 303 amino acids that exhibits 29% identity to the US2 protein of herpes simplex virus 1. EUS1 is expressed as a 2.3-kb mRNA of the gamma-1 class, as its synthesis begins prior to viral DNA replication at 4 hr p.i. but is retarded by phosphonoacetic acid, an inhibitor of viral DNA replication. The Tci and Tct sites of EUS1 were mapped by S1 nuclease analyses to nts 13,637 and 11,408, respectively. Interestingly, this termination site is also utilized by three late mRNAs of 5.8, 3.8, and 1.7 kb which originate within the Us and overlap the IR6 mRNA encoded in the terminal inverted repeat (TR) of the prototype genomic isomer. EUS1 is 3' coterminal with IR6 in the inverted repeat, whereas, the 5.8, 3.8, and 1.7 kb transcripts are 3' coterminal with IR6 of the TR.
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Affiliation(s)
- C A Breeden
- Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130-3932
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Flowers CC, O'Callaghan DJ. Equine herpesvirus 1 glycoprotein D: mapping of the transcript and a neutralization epitope. J Virol 1992; 66:6451-60. [PMID: 1383565 PMCID: PMC240137 DOI: 10.1128/jvi.66.11.6451-6460.1992] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Studies with molecular and immunological techniques identified and mapped the transcript encoding glycoprotein D (gD) of equine herpesvirus 1 KyA, as well as two continuous gD antigenic determinants. Three mRNA species of 5.5, 3.8, and 1.7 kb overlap the gD open reading frame and are transcribed from the DNA strand encoding gD. Northern (RNA) blot hybridization with both DNA clones and riboprobes, as well as S1 nuclease analyses, showed the 3.8-kb mRNA to encode gD and to be synthesized as a late (beta-gamma) transcript. The 3.8-kb gD mRNA initiates within the US segment 91 and 34 nucleotides downstream of the CCAAT and TATA elements, respectively, and encodes a potential polypeptide of 392 amino acids. The termination site of this transcript maps within the terminal repeat at a site also used by the 5.5-kb mRNA and the IR6-encoded 1.2-kb mRNA, such that these three transcripts form a 3'-coterminal nested set. The extended size (2,250 nucleotides) of the 3' untranslated region of the gD transcript and its termination within the terminal repeat may result from the deletion of 3,859 bp, which eliminates two consensus polyadenylation signals downstream of the gD open reading frame of EHV-1 KyA. Use of antisera to synthetic peptides of 19 amino acids (residues 4 to 22) and 20 amino acids (residues 267 to 285) in Western immunoblot analyses revealed that gD is present in EHV-1 virions as a 55-kDa polypeptide. In addition, these antisera detected the 55-kDa protein as well as 58- and 47-kDa polypeptides in infected-cell extracts at late times of infection. Residues 4 to 22 make up a continuous neutralizing epitope of gD, since incubation of equine herpesvirus 1 with the anti-19-mer serum prior to infection results in reduced numbers of plaques and reduced levels of virus-encoded thymidine kinase. Complement is not required for neutralization mediated by the anti-19-mer serum.
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Affiliation(s)
- C C Flowers
- Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130-3932
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Zhao Y, Holden VR, Harty RN, O'Callaghan DJ. Identification and transcriptional analyses of the UL3 and UL4 genes of equine herpesvirus 1, homologs of the ICP27 and glycoprotein K genes of herpes simplex virus. J Virol 1992; 66:5363-72. [PMID: 1323700 PMCID: PMC289092 DOI: 10.1128/jvi.66.9.5363-5372.1992] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The DNA sequence of 3,240 nucleotides of the XbaI G fragment located in the unique long (UL) region of the equine herpesvirus 1 genome revealed two major open reading frames (ORFs) designated UL3 and UL4. The UL3 ORF of 470 amino acids (aa) maps at nucleotides (nt) 4450 to 3038 from the long terminus, and its predicted 51.4-kDa protein product exhibits significant homology to the ICP27 alpha regulatory protein of herpes simplex virus type 1 (HSV-1; 32% identity) and to the ORF4 protein of varicella-zoster virus (13% identity). Interestingly, a zinc finger motif is conserved in the C-terminal domains of both ICP27 of HSV-1 (aa 483 to 508) and UL3 of equine herpesvirus 1 (aa 441 to 466). The UL4 ORF of 343 aa maps at nt 5618 to 4587 and could encode a protein of 38.1 kDa which exhibits significant homology to the UL53 protein (cell fusion protein or glycoprotein K) of HSV-1 (26% identity) and to the ORF5 protein of varicella-zoster virus (33% identity). Analyses of the UL4 amino acid sequence revealed domains characteristic of a membrane-bound glycoprotein and included potential signature sequences for (i) a signal sequence, (ii) two N-linked glycosylation sites, and (iii) four transmembrane domains. Nucleotide sequence analyses also revealed potential TATA boxes located upstream of the UL3 and UL4 ORFs. However, only a single polyadenylation signal (nt 2988 to 2983) was detected downstream of the UL3 ORF. Northern (RNA) blot hybridization and S1 nuclease analyses were used to map and characterize the UL3 and UL4 mRNAs. Metabolic inhibitors were used to identify the kinetic class of these two genes. The data revealed that UL3 is an early gene that encodes a 1.6-kb mRNA, while UL4 is a late gene encoding a 3.8-kb mRNA that overlaps the UL3 transcript. Both transcripts were shown by S1 nuclease analyses to initiate 24 to 26 nt downstream of their respective TATA boxes and to have a common transcription termination signal as a pair of 3'-coterminal mRNAs.
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Affiliation(s)
- Y Zhao
- Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130-3932
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58
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Abstract
Sequences encoding the UL1 gene of equine herpesvirus type 1 (EHV-1) are conserved in the genome of EHV-1 defective interfering particles (DIPs) that mediate oncogenic transformation and persistent infection. The UL1 protein was identified by in vitro transcription/translation and hybrid-arrest translation analyses which employed a UL1/pGEM-3Z construct designated pGEML1. SDS-PAGE analyses of in vitro translation products synthesized from UL1-specific RNA revealed that the UL1 ORF encodes a 30 kDa protein which corresponds in size to the 258 amino acid protein predicted by DNA sequence analyses. This result was confirmed by arresting translation of the in vitro transcribed UL1 RNA with an oligodeoxynucleotide complementary to UL1 coding sequences. The UL1 protein is a homolog of the predicted protein encoded by the ORF2 gene of varicella-zoster virus, but UL1 has no homolog in herpes simplex virus type 1. The UL1 protein contains a region conforming to a 'PEST' (Proline, Glutamic acid, Serine, and Threonine) sequence, which is commonly found in proteins with half-lives of less than two hours.
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Affiliation(s)
- R N Harty
- Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130-3932
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Abstract
The complete DNA sequence was determined of a pathogenic British isolate of equine herpesvirus-1, a respiratory virus which can cause abortion and neurological disease. The genome is 150,223 bp in size, has a base composition of 56.7% G + C, and contains 80 open reading frames likely to encode protein. Since four open reading frames are duplicated in the major inverted repeat, two are probably expressed as a spliced mRNA, and one may contain an internal transcriptional promoter, the genome is considered to contain 76 distinct genes. The genes are arranged collinearly with those in the genomes of the two previously sequenced alphaherpesviruses, varicella-zoster virus, and herpes simplex virus type-1, and comparisons of predicted amino acid sequences allowed the functions of many equine herpesvirus 1 proteins to be assigned.
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Affiliation(s)
- E A Telford
- Institute of Virology, University of Glasgow, United Kingdom
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Holden VR, Yalamanchili RR, Harty RN, O'Callaghan DJ. Identification and characterization of an equine herpesvirus 1 late gene encoding a potential zinc finger. Virology 1992; 188:704-13. [PMID: 1316680 DOI: 10.1016/0042-6822(92)90525-t] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In this report, we present the DNA sequence and transcriptional characterization of a gene (IR5) that maps within each of the inverted repeat (IR) segments of the equine herpesvirus type 1 (EHV-1) genome. The IR5 open reading frame (ORF) is located within both IR sequences (nucleotides 9932-10,642 of the IR). DNA sequence analyses of the IR5 gene region revealed an ORF of 236 amino acids (24,793 Da) that showed significant homology to ORF64 of varicella-zoster virus and ORF3 of EHV-4 both of which map within the inverted repeats and to the US10 ORF of herpes simplex virus type 1 (HSV-1) which maps within the unique short segment. Additional analyses of the nucleotide sequence failed to reveal any overlapping ORFs that would correspond to US11 or US12 of HSV-1. Interestingly, the IR5 ORF of EHV-1 possesses a sequence of 13 amino acids (CAYWCCLGHAFAC) that is a perfect match to the consensus zinc finger motif (C-X2-4-C-X2-15-C/H-X2-4-C/H). Putative cis-acting elements flanking the IR5 ORF include a TATA box (nucleotides 9864-9870), a CAAT box (nucleotides 9709-9714), and a polyadenylation signal (nucleotides 10,645-10,650). Northern blot and S1 nuclease analyses identified a single 0.9-kb mRNA species that first appears at 2 hr postinfection, and whose synthesis is reduced in the presence of phosphonoacetic acid, an inhibitor of EHV-1 DNA synthesis. Thus, the IR5 gene of EHV-1 exhibits characteristics representative of a late gene of the gamma-1 class. The characterization of the IR5 gene at the DNA and RNA levels will facilitate ongoing studies to identify and characterize the IR5 polypeptide.
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Affiliation(s)
- V R Holden
- Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130-3932
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Holden VR, Harty RN, Yalamanchili RR, O'Callaghan DJ. The IR3 gene of equine herpesvirus type 1: a unique gene regulated by sequences within the intron of the immediate-early gene. DNA SEQUENCE : THE JOURNAL OF DNA SEQUENCING AND MAPPING 1992; 3:143-52. [PMID: 1335300 DOI: 10.3109/10425179209034010] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The complete nucleotide sequence of the inverted repeat component (IR; 12,776 bp each) of the genome of equine herpesvirus type 1 (EHV-1) has been determined. Transcription analyses have revealed that the EHV-1 IR sequence encodes at least 6 genes. In this report, we present the DNA sequence and transcriptional characterization of a gene (IR3) that maps entirely within the IR sequences. The IR3 open reading frame (ORF) is located between nucleotides (nt) 6123-6411 of the IR sequence and possesses an ORF of 95 amino acids. Interestingly, this ORF does not show homology to any known herpesvirus gene, suggesting that the IR3 gene is unique to EHV-1. Moreover, the location of the IR3 gene between the immediate-early (IR1) gene and the origin of replication is unique in comparison to the IR gene arrangement of other alphaherpesviruses such as herpes simplex virus type 1 and varicella zoster virus. Putative cis-acting elements flanking the IR3 ORF include a TATA box (nt 5648-5652), a GC box (nt 5600-5605), and three polyadenylation signals (nt 6533-6538, 6648-6653, and 6663-6668). Northern blot analyses identified a 1.0 kb mRNA that exhibits characteristics of a late gene of the gamma-1 class. Northern blot, S1 nuclease, and primer extension analyses revealed that transcription of IR3 initiates within the intron of the immediate-early gene (IR1) on the opposite stand of the genome. Thus, the 5' end of IR3 transcript is antisense to the 5' end of the IR1 mRNA and promoter, and IR3 transcription may regulate the expression of IR1 during late times of infection.
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Affiliation(s)
- V R Holden
- Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130-3932
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