Identification and characterization of the herpes simplex virus type 1 protein encoded by the UL37 open reading frame

Abstract

The UL37 open reading frame of the herpes simplex virus type 1 (HSV-1) DNA genome is located between map units 0.527 and 0.552. We have identified and characterized the UL37 protein product in HSV-1-infected cells. The presence of the UL37 protein was detected by using a polyclonal rabbit antiserum directed against an in vitro-translated product derived from an in vitro-transcribed UL37 mRNA. The UL37 open reading frame encodes for a protein with an apparent molecular mass of 120 kDa in HSV-i-infected cells; the protein's mass was assigned on the basis of its migration in sodium dodecyl sulfate-polyacrylamide gels. The UL37 protein is not present at detectable levels in purified HSV-1 virions, suggesting that it is not a structural protein. Analysis of time course experiments and experiments using DNA synthesis inhibitors demonstrated that the UL37 protein is expressed prior to the onset of viral DNA synthesis, reaching maximum levels late in infection, classifying it as a 'yl gene. Elution of HSV-1-infected cell proteins from single-stranded DNA agarose columns by using a linear KCI gradient demonstrated that the UL37 protein elutes from this matrix at a salt concentration similar to that observed for ICP8, the major HSV-1 DNA-binding protein. In addition, computer-assisted analysis revealed a potential ATP-binding domain in the predicted UL37 amino acid sequence. On the basis of the kinetics of appearance and DNA-binding properties, we hypothesize that UL37 represents a newly recognized HSV-1 DNA-binding protein that may be involved in late events in viral replication. * Corresponding author. in cells infected by HSV-1 in the presence of DNA synthesis inhibitors and therefore was initially identified as an early (,) transcript on the basis of the nomenclature at the time for the different temporal classes of HSV genes. In this study, we report on the identification and characterization of the UL37 protein from HSV-1-infected cells. Our results demonstrate that the UL37 ORF encodes a protein with an apparent molecular mass of 120 kDa, which is nonstructural, belongs to the-yl class of HSV genes, and binds to single-stranded (SS) DNA-agarose columns. A search of the predicted UL37 amino acid sequence reveals a potential ATP-binding site, and computer-assisted analysis comparing the UL37 sequence with the entire varicella-zoster virus (VZV) genome demonstrates that the VZV homolog, gene 21, shares 47% similarity at the amino acid level with UL37. While we currently have not identified a specific function for the UL37 protein, we hypothesize, on the basis of the results presented in this report, that the UL37 protein is a newly recognized HSV-1 DNA-binding protein which may play a role either in viral gene regulation or in the processing of newly synthesized viral DNA. MATERIALS AND METHODS Cells and viruses. Vero and CV-1 cells (American Type Culture Collection) and human thymidine kinase-negative (TK-) 143 cells were grown in Eagle's minimal essential medium supplemented with 10% (vol/vol) Serum-Plus (Hazleton Co...

Cytosolic herpes simplex virus capsids not only require binding inner tegument protein pUL36 but also pUL37 for active transport prior to secondary envelopment

“…Expression of UL37GFP was detected at 147 kDa as early as 6 h post infection (PI); the slightly higher molecular weight of UL37GFP expressed by HSV1(17 + )‐vUL37‐GFP was due to a linker between pUL37 and GFP. As the infection progressed, the anti‐GFP antibody detected a second band around 120 kDa; a corresponding smaller band has also been described for untagged pUL37 (Shelton et al ., ; Desai et al ., ). CheVP26 was expressed as early as 6 h PI with HSV1(17 + )Lox‐CheVP26, and at 8 h with HSV1(17 + )Lox‐CheVP26‐UL37GFP, similarly as VP26 by HSV1(17 + )‐vUL37‐GFP.…”

“…The HSV1 open reading frame UL37 encodes another essential inner tegument protein of 1123 aa and 120 kDa (Shelton et al ., ; Desai et al ., ; Leege et al ., ; Roberts et al ., ). This gene is also conserved in alpha‐, beta‐ and gammaherpesvirinae; the homologous proteins are called p21 in varicella zoster virus, pUL47 in HCMV, pUL30 in the human herpesvirus 6 and 7, BOLF1 in Epstein–Barr virus and ORF63 in KSHV (Mocarski, ; Kelly et al ., ).…”

The spontaneous reactivation function of the herpes simplex virus type 1 LAT gene resides completely within the first 1.5 kilobases of the 8.3-kilobase primary transcript

“…The insertion was at an AflII site between the 5Ј ends of UL37 and UL38 (genomic nt 84252). UL37 and UL38 are both gamma genes that require only the first 29 to 34 nt upstream of the mRNA cap site for transcriptional activity (8,14,30,31). The AflII site that we converted to a PacI site and into which we then cloned the LAT insert is located 36 nt upstream of the UL37 cap site and 126 nt upstream of the UL38 cap site.…”

Polymorphism within the herpes simplex virus (HSV) ribonucleotide reductase large subunit (ICP6) confers type specificity for recognition by HSV type 1-specific cytotoxic T lymphocytes

“…The UL39 gene encodes the ribonucleotide reductase large subunit (ICP6, RR1), which is part of the HSV ribonucleotide reductase which reduces ribonucleotides to deoxyribonucleotides for the production of precursors necessary for viral DNA synthesis (20,54). The UL37 gene encodes a protein of unknown function (58).…”