The protease of herpes simplex virus type 1 is essential for functional capsid formation and viral growth

The herpes simplex virus type 1 protease and related proteins are involved in the assembly of viral capsids. The protease encoded by the UL26 gene can process itself and its substrate ICP35, encoded by the UL26.5 gene. To better understand the functions of the protease in infected cells, we have isolated a complementing cell line (BMS-MG22) and constructed and characterized a null UL26 mutant virus, m100. The mutant virus failed to grow on Vero cells and required a complementing cell line for its propagation, confirming that the UL26 gene product is essential for viral growth. Phenotypic analysis of m100 shows that (i) normal amounts of the c and d forms of ICP35 were produced, but they failed to be processed to the cleaved forms, e and f; (ii) viral DNA replication of the mutant proceeded at near wild-type levels, but DNA was not processed to unit length or encapsidated; (iii) capsid structures were observed in thin sections of m100-infected Vero cells by electron microscopy, but assembly of VP5 into hexons of the capsid structure was conformationally altered; and (iv) nuclear localizations of the protease and ICP35 are independent of each other, and the function(s) of Na, at least in part, is to direct the catalytic domain N(o) to the nucleus.

Involvement of mu opioid receptors of periaqueductal gary (PAG) in acupuncture inhibition of noxious blood pressure response in rabbits

Strong electric shock stimulation of the rabbit front paw elicited a pressor blood pressure response regarded as noxious response. Ligands of mu opioid receptors were microinjected into the PAG to observe their effects on acupunture inhibition of the pressor response. (1) Ohmefentanyl (OMF), a mu agonist, significantly attenuated the pressor response. Mu antagonist TCTAP greatly enhanced the pressor response. (2) Electroacupuncture (EA) significantly inhibited the pressor response, the inhibition being readily reversed by TCTAP. The response after TCTAP was significantly greater than that of the control before EA. The results suggest that noxious stimulation is able to activate the mu opioid receptor of the PAG to modulate the noxious response and EA is able to enhance the activation.

Preliminary report on cardiovascular responses to urapidil during intubation and extubation

Urapidil (Ebrantil), a new antihypertensive agent with central and peripheral sites of action, has proven effective in the management of both chronic and acute hypertension. This study investigates its effects on cardiovascular responses during intubation and extubation under general anesthesia. Thirty normotensive patients (ASA I-II) were randomized into control (I, without urapidil, n = 10); lower dose (II, 0.4 mg/kg, n = 10); and higher dose (III, 0.6 mg/kg, n = 10) groups. A significant fall of blood pressure was observed in all patients within 1 min after urapidil administration (P < 0.05), and the magnitude of the decrease was related to blood pressure before treatment. However, no transient drop of blood pressure to hypotensive values was observed. The results suggest that urapidil could be used under general anesthesia in patients to control fluctuating blood pressure during intubation and extubation. The increased heart rate (P < 0.05) seen for several minutes after urapidil administration may have been due to the patients' hypovolemic state.

Monitoring of total chromium in rat fluids and lymphocytes following intratracheal administration of soluble trivalent or hexavalent chromium compounds

1. Intratracheal instillation of sodium dichromate (CrVI) and chromium acetate hydroxide (CrIII) to male Wistar rats gave rise to increased chromium concentrations in whole blood, plasma and urine up to 72 h post exposure; peak concentrations were reached at 6 h after exposure. 2. The ratio of whole blood chromium to plasma chromium concentrations was significantly different for Cr(VI) and Cr(III) treatments. Both blood chromium and plasma chromium assays should therefore be used for the assessment of chromium exposure. 3. Chromium was also detected in peripheral lymphocytes. Cr(VI), but not Cr(III) accumulated significantly in the lymphocytes after treatment. These cells have potential to be used for biomarkers of the assessment of exposure to chromium compounds.

The C-terminal third of UL42, a HSV-1 DNA replication protein, is dispensable for viral growth

UL42 is the herpes simplex virus type 1 DNA polymerase (Pol) accessory protein and is required for viral DNA replication and growth. Previous results from this laboratory demonstrated that the N-terminal two thirds of the protein contains all of the biochemical activities of the protein which can be measured in vitro. These activities include dsDNA-binding, association with DNA polymerase, and stimulation of polymerase activity. To better understand the functions of UL42 in infected cells, we have isolated and characterized two viral recombinants, UL42lacZ and n338. In the mutant virus UL42lacZ, the UL42 gene was disrupted by insertion of the Escherichia coli lacZ gene, while in the mutant virus n338, a termination codon was introduced after amino acid position 338. Analysis of the mutant phenotypes suggest that (1) the first 338 residues of UL42 retain all the functions necessary for viral DNA replication and growth in lytic infection, (2) localization of UL42 to the cell nucleus is independent of Pol, and (3) localization of ICP8 (ssDNA-binding protein) to prereplication sites is independent of functional UL42.

Intragenic complementation of herpes simplex virus ICP8 DNA-binding protein mutants

The major DNA-binding protein, or infected-cell protein 8 (ICP8), of herpes simplex virus is required for viral DNA synthesis and normal regulation of viral gene expression. Previous genetic analysis has indicated that the carboxyl-terminal 28 residues are the only portion of ICP8 capable of acting independently as a nuclear localization signal. In this study, we constructed a mutant virus (n11SV) in which the carboxyl-terminal 28 residues of ICP8 were replaced by the simian virus 40 large-T-antigen nuclear localization signal. The n11SV ICP8 localized into the nucleus and bound to single-stranded DNA in vitro as tightly as wild-type ICP8 did but was defective for viral DNA synthesis and viral growth in Vero cells. Two mutant ICP8 proteins (TL4 and TL5) containing amino-terminal alterations could complement the n11SV mutant but not ICP8 gene deletion mutants. Cell lines expressing TL4 and TL5 ICP8 were isolated, and in these cells, complementation of n11SV was observed at the levels of both viral DNA replication and viral growth. Therefore, complementation between n11SV ICP8 and TL4 or TL5 ICP8 reconstituted wild-type ICP8 functions. Our results demonstrate that (i) the carboxyl-terminal 28 residues of ICP8 are required for a function(s) involved in viral DNA replication, (ii) this function can be supplied in trans by another mutant ICP8, and (iii) ICP8 has multiple domains possessing different functions, and at least some of these functions can complement in trans.

Hexavalent chromium produces DNA strand breakage but not unscheduled DNA synthesis at sub-cytotoxic concentrations in hepatocytes

Rat hepatocytes were used to investigate the possible induction of unscheduled DNA synthesis (UDS) and the extent of DNA strand breaks induced by sodium dichromate (a representative chromium(VI) compound) and chromium acetate hydroxide (chromium(III)) in vitro. Cytotoxicity, measured using tetrazolium salt (MTT) reduction assay, was found at a much higher dose of chromium(III), (> 50 microM), compared to that of chromium(VI), (> 2.5 microM), in cultured hepatocytes over 20 h treatment at 37 degrees C. Chromium(VI), but not chromium(III), stimulated minimal UDS in hepatocytes at sub-cytotoxic concentrations. A positive UDS response was only observed at cytotoxic concentration. DNA strand breaks in hepatocytes were induced by chromium(VI) following incubation at 37 degrees C for 1 h at doses of 10, 20 and 40 microM sodium dichromate. The subsequent ligation of such strand breaks in hepatocytes treated with 40 microM chromium(VI) for 1 h at 37 degrees C was demonstrated. The majority of strand breaks was repaired within 30 min following removal of the chromate. In conclusion, chromate-induced DNA strand breakage, possibly involving the formation of oxygen radicals and lack of significant UDS have some analogy to those produced by ionizing radiation.

Microvascular geometry of the rat heart. Arteriolar and venular capillary regions

The importance of realistic data regarding microvascular geometry for the understanding of oxygen transport to tissue cannot be underestimated. The purpose of the present investigation was therefore to determine the pattern of capillarization in rat myocardium. The histochemical method used in this study was novel in that it allowed for the discrimination of arteriolar capillary (AC) and venular capillary (VC) regions on the basis of color. Our preeminent finding was that systematic differences exist in microvascular geometry from arteriolar to venular capillary regions in normal rat myocardium. Specifically, VC regions are characterized by greater capillary density; more uniform capillary spacing; shorter segment lengths; and increased capillary diameter. These differences translate to significantly greater capillary length, surface and volume densities on the venular side of the capillary bed. In the face of lower PO2 values towards venules, this distinctive geometry would serve to provide advantageous geometric conditions for oxygen diffusion.

Production of 8-hydroxydeoxyguanosine in isolated DNA by chromium(VI) and chromium(V)

Chromium(VI) and Cr(V) compounds increased the concentration of 8-hydroxydeoxyguanosine (oh8dG) in isolated DNA, whereas no such increase was seen with Cr(III). Furthermore, incubating DNA with H2O2 and Cr(VI) or Cr(V) potentiated the formation of oh8dG above levels observed with either chromium compound alone. In the presence of catalase, the increase in DNA oxidation observed with Cr(VI) was inhibited, the base oxidation observed being equivalent to background levels, and this indicated involvement of H2O2 in the mechanism. Glutathione did not enhance chromium-induced formation of this oxidized base. These results help to explain a mechanism of chromium-induced DNA oxidation involving H2O2 via a Fenton-type reaction.

Distal protein sequences can affect the function of a nuclear localization signal

The major DNA-binding protein, or infected-cell protein 8 (ICP8), encoded by herpes simplex virus can localize to the cell nucleus independently of other viral proteins. To define the nuclear localization signals within ICP8, we performed several forms of mutagenesis on the cloned ICP8 gene. Deletion analysis of the ICP8 gene showed that several portions of ICP8 are involved in its nuclear localization. To determine whether these regions were independent localization signals, we introduced various portions of the ICP8 gene into a series of cassette plasmids which allowed expression of fusion proteins containing pyruvate kinase, normally a cytoplasmic protein, fused to various portions of ICP8. These results showed that the carboxyl-terminal 28 residues are the only portion of ICP8 capable of targeting protein kinase into the nucleus. However, inclusion of certain additional regions of ICP8 into the fusion protein led to an inhibition of nuclear localization. Therefore, the carboxyl-terminal 28 residues of ICP8 can act independently as a nuclear localization signal, but certain conformational constraints or folding or assembly requirements in the remainder of the protein can affect the nuclear localization of the protein. Our results demonstrate that sequences distant from a nuclear localization signal can affect its ability to function. A set of fusion vectors has been isolated which should be of general use for making 5' or 3' fusions in any reading frame to rapidly map localization signals.

Induction of DNA strand breaks in peripheral lymphocytes by soluble chromium compounds

1. Incubation of human lymphocytes with sodium dichromate (CrVI) at 37 degrees C for 3 h resulted in a dose-dependent increase in DNA strand breaks without concurrent cytotoxicity. In contrast, chromium acetate hydroxide (CrIII) failed to induce DNA strand breaks at sub-cytotoxic concentrations. 2. DNA strand breaks were also detected in the peripheral lymphocytes of Wistar rats, 24 h after intratracheal instillation of sodium dichromate (1.3 and 2.5 mg kg-1). Instillation of chromium acetate hydroxide (up to 21.8 mg kg-1) failed to induce DNA strand breaks in peripheral lymphocytes. In accord with previous studies, hexavalent chromium was found to be more readily absorbed from the lungs into the peripheral blood than chromium in its trivalent form. 3. The results of this study indicate that fluorometric analysis of DNA unwinding (FADU) in peripheral lymphocytes might be a convenient method of measuring an important biological effect of chromium in occupationally-exposed workers.

Association between the herpes simplex virus major DNA-binding protein and alkaline nuclease

Herpes simplex virus encodes seven proteins which have been shown to be both necessary and sufficient for in vitro replication of origin-containing plasmids. We have shown previously that one of these proteins, the major DNA-binding protein mDBP, forms a complex with alkaline nuclease, which is not one of the seven essential proteins. In this study, we have employed immunological reagents and a series of deletion mutants to investigate this complex further. We have determined the regions of mDBP which are important in the formation of this complex, and we have shown that the intranuclear locations of alkaline nuclease and major DNA-binding protein overlap.

EXPRESSION OF C-fos PROTEIN IN SEROTONERGIC NEURONS OF RAT BRAINSTEM FOLLOWING ELECTRO-ACUPUNCTURE

The c-fos proto-oncogene encodes a nuclear phosphoprotein, Fos which has been proposed to be a "third messenger" coupling short term extracellular signals to long term alteration in cell function. Using double labeling immunocytochemistry, the present work demonstrated the co-localization of Fos protein and serotonin in the nucleus raphe dorsalis, nucleus raphe centralis superior and rostral ventromedial medulla. The results pose an interesting problem, the possible relation of Fos protein to the biosynthesis of serotonin, awaiting further investigation.

Photodynamic therapy for 50 patients with skin cancers or precancerous lesions

Hematoporphyrin photodynamic therapy (HpD-PDT) was used to treat 50 patients (51 lesions) with skin cancers or precancerous lesions. The preliminary results were satisfactory, with 44 cases (45 lesions) obtaining excellent results, 4 cases good, 1 case fair, and 1 case poor. The effective rate was 98%, the significant remission rate 96%, and the complete remission rate 88.2%. Exposure to sunlight should be avoided after HpD injection, since it produces photosensitivity. A follow-up for 1 to 3 years confirmed that HpD-PDT is a good new adjuvant therapy for selected cases. It brings a hopeful future to the treatment of skin cancers.

Potential role for herpes simplex virus ICP8 DNA replication protein in stimulation of late gene expression

We have identified a trans-dominant mutant form of the herpes simplex virus (HSV) DNA-binding protein ICP8 which inhibits viral replication. When expressed by the V2.6 cell line, the mutant gene product inhibited wild-type HSV production by 50- to 150-fold when the multiplicity of infection was less than 5. Production of HSV types 1 and 2 but not production of pseudorabies virus was inhibited in V2.6 cells. The inhibitory effect was not due solely to the high levels of expression, because the levels of expression were comparable to those in the permissive wild-type ICP8-expressing S-2 cell line. Experiments designed to define the block in viral production in V2.6 cells demonstrated (i) that viral alpha and beta gene expression was comparable in the different cell lines, (ii) that viral DNA replication proceeded but was reduced to approximately 20% of the control cell level, and (iii) that late gene expression was similar to that in cells in which viral DNA replication was completely blocked. Genetic experiments indicated that the mutant gene product inhibits normal functions of ICP8. Thus, ICP8 may play distinct roles in replication of viral DNA and in stimulation of late gene expression. The dual roles of ICP8 in these two processes could provide a mechanism for controlling the transition from viral DNA synthesis to late gene expression during the viral growth cycle.

Correct intranuclear localization of herpes simplex virus DNA polymerase requires the viral ICP8 DNA-binding protein

We used indirect immunofluorescence to examine the factors determining the intranuclear location of herpes simplex virus (HSV) DNA polymerase (Pol) in infected cells. In the absence of viral DNA replication, HSV Pol colocalized with the HSV DNA-binding protein ICP8 in nuclear framework-associated structures called prereplicative sites. In the presence of viral DNA replication, HSV Pol colocalized with ICP8 in globular intranuclear structures called replication compartments. In cells infected with mutant viruses encoding defective ICP8 molecules, Pol localized within the cell nucleus but showed a general diffuse intranuclear distribution. In uninfected cells transfected with a plasmid expressing Pol, Pol similarly showed a diffuse intranuclear distribution. Therefore, Pol can localize to the cell nucleus without other viral proteins, but functional ICP8 is required for Pol to localize to prereplicative sites. In cells infected with mutant viruses encoding defective Pol molecules, ICP8 localized to prereplicative sites. Thus, Pol or the portions of Pol not expressed by the mutant viruses are not essential for the formation of prereplicative sites or the localization of ICP8 to these structures. These results demonstrate that a specific nuclear protein can influence the intranuclear location of another nuclear protein.

Simplified fluorometric assay of total selenium in plasma and urine

We describe here a single-tube assay that may be applied to the whole range of selenium status in adult and pediatric patients, including depletion during parenteral or other nutrition. A specimen or aqueous standard, 100 microL, is digested with 0.5 mL of HNO3/HCIO4 (4/1 by vol, at 190 degrees C for 90 min), reduced with 0.5 mL of concentrated HCI (150 degrees C, 30 min), and complexed with 0.5 mL of 6.3 mmol/L 2,3-diaminonaphthalene (DAN) reagent in the presence of EDTA (60 degrees C, 30 min). The resulting fluorophore is extracted into cyclohexane and its fluorescence measured (excitation at 366 nm; emission at 544 nm). It is not necessary to control pH during the complexing step or to protect the DAN from light. The limit of detection of selenium is 10 micrograms/L (0.126 mumol/L); linearity of results extends to 2000 micrograms/L (25.3 mumol/L). Between-batch precision is 5%, analytical recovery 90%-96%. Performance is good as tested against Reference Materials and by participation in a National Quality Assurance Scheme.

Simplified fluorometric assay of total selenium in plasma and urine

We describe here a single-tube assay that may be applied to the whole range of selenium status in adult and pediatric patients, including depletion during parenteral or other nutrition. A specimen or aqueous standard, 100 microL, is digested with 0.5 mL of HNO3/HCIO4 (4/1 by vol, at 190 degrees C for 90 min), reduced with 0.5 mL of concentrated HCI (150 degrees C, 30 min), and complexed with 0.5 mL of 6.3 mmol/L 2,3-diaminonaphthalene (DAN) reagent in the presence of EDTA (60 degrees C, 30 min). The resulting fluorophore is extracted into cyclohexane and its fluorescence measured (excitation at 366 nm; emission at 544 nm). It is not necessary to control pH during the complexing step or to protect the DAN from light. The limit of detection of selenium is 10 micrograms/L (0.126 mumol/L); linearity of results extends to 2000 micrograms/L (25.3 mumol/L). Between-batch precision is 5%, analytical recovery 90%-96%. Performance is good as tested against Reference Materials and by participation in a National Quality Assurance Scheme.

Guinea pig cytomegalovirus immediate-early transcription

Guinea pig cytomegalovirus (GPCMV) immediate-early (IE) gene expression was analyzed. GPCMV IE RNA was defined as RNA obtained from GPCMV-infected guinea pig cells treated with cycloheximide for 1 h before infection and for 4 h postinfection. Mapping studies showed that GPCMV IE genes are located at several distinct sites on the GPCMV genome. A total of 17 GPCMV IE transcripts were identified, and 9 IE transcripts coded for by three specific regions of the genome (regions I, II, and III) were characterized in detail. A series of recombinant DNA clones were generated to identify the nine IE transcripts. Three of the IE transcripts from region I and three from region III were transcribed in the same direction from overlapping sequences. The 2.0-kilobase (kb) transcript encoded by the EcoRI E DNA fragment (region II) was the most abundant IE GPCMV transcript. The cloned GPCMV DNA subfragment that was used to identify the region II EcoRI E 2.0-kb transcript did not hybridize to GPCMV early or late RNA, indicating that this transcript is expressed only under IE conditions. Expression of RNAs from the IE genes was also measured during a natural GPCMV infection in the absence of cycloheximide. During the natural infection, the transcripts previously identified under IE cycloheximide block conditions were expressed, and the region II EcoRI E 2.0-kb transcript was the most abundant transcript at 1 h postinfection. In addition, a rise and fall in RNA levels was observed during the natural infection, demonstrating the transient nature of expression of these transcripts. We conclude that GPCMV IE gene expression is complex, involving a reasonably large number of genes, and demonstrates some similarities with IE transcription by other CMVs.

[Observations of the incidence of metastases form forestomach carcinoma following fractioned laser hyperthermia]

In order to evaluate the effect of local tumor hyperthermia on the incidence of distant metastases, transplantable forestomach carcinomas in 615-strain mice were treated by YAG laser hyperthermia in two trials. The results showed that the increased incidences of metastases following treatment at heating conditions of 41 degrees C/10 min, 41 degrees C/20 min, 45 degrees C/10 min and 45 degrees C/20 min were not statistically significant. Tumor growth inhibition laser hyperthermia at 45 degrees C/20 min was more effective than that under other heating conditions.

Genetic evidence for multiple nuclear functions of the herpes simplex virus ICP8 DNA-binding protein

We have isolated several mutant herpes simplex viruses, specifically mutated in the infected cell protein 8 (ICP8) gene, to define the functional domains of ICP8, the major viral DNA-binding protein. To facilitate the isolation of these mutants, we first isolated a mutant virus, HD-2, with the lacZ gene fused to the ICP8 gene so that an ICP8-beta-galactosidase fusion protein was expressed. This virus formed blue plaques on ICP8-expressing cell lines in the presence of 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside. Mutated ICP8 gene plasmids cotransfected with HD-2 DNA yielded recombinant viruses with the mutant ICP8 gene incorporated into the viral genome. These recombinants were identified by formation of white plaques. Four classes of mutants were defined: (i) some expressed ICP8 that could bind to DNA but could not localize to the cell nucleus; (ii) some expressed ICP8 that did not bind to DNA but localized to the nucleus; (iii) some expressed ICP8 that neither bound to DNA nor localized to the nucleus; and (iv) one expressed ICP8 that localized to the cell nucleus and bound to DNA in vitro, but the mutant virus did not replicate its DNA. These classes of mutants provide genetic evidence that DNA binding and nuclear localization are distinct functions of ICP8 and that ICP8 has nuclear functions other than binding to DNA. Furthermore, the portion of ICP8 needed for a nuclear function(s) distinct from DNA binding is the part of ICP8 showing sequence similarity to that of the cellular protein cyclin or proliferating cell nuclear antigen.

Common nodABC genes in Nod locus 1 of Azorhizobium caulinodans: nucleotide sequence and plant-inducible expression

Azorhizobium caulinodans strain ORS571 induces nitrogen-fixing nodules on roots and stem-located root primordia of Sesbania rostrata. Two essential Nod loci have been previously identified in the bacterial genome, one of which (Nod locus 1) shows weak homology with the common nodC gene of Rhizobium meliloti. Here we present the nucleotide sequence of this region and show that it contains three contiguous open reading frames (ORFA, ORFB and ORFC) that are related to the nodABC genes of Rhizobium and Bradyrhizobium species. ORFC is followed by a fourth (ORF4) and probably a fifth (ORF5) open reading frame. ORF4 may be analogous to the nodI gene of R. leguminosarum, whereas ORF5 could be similar to the rhizobial nodF genes. Coordinated expression of this set of five genes seems likely from the sequence organization. There is no typical nod promoter consensus sequence (nod box) in the region upstream of the first gene (ORFA) and there is no nodD-like gene. LacZ fusions constructed with ORFA, ORFB, ORFC, and ORF4 showed inducible beta-galactosidase expression in the presence of S. rostrata seedlings as well as around stem-located root primordia. Among a series of phenolic compounds tested, the flavanone naringenin was the most efficient inducer of the expression of this ORS571 nod gene cluster.

Genetic identification of a portion of the herpes simplex virus ICP8 protein required for DNA-binding

The major DNA-binding protein or infected cell protein 8 (ICP8) encoded by herpes simplex virus exhibits multiple interactions with the cell nucleus in that it interacts with the host cell nuclear matrix and viral DNA molecules as sequential stages in its maturational process (M. P. Quinlan, L. B. Chen, and D. M. Knipe (1984), Cell 36, 857-868). To define the portion(s) of ICP8 required for DNA binding, we have fine-mapped and identified the sequence changes in mutant genes causing changes in the protein that affect DNA binding. These mutations lead to amino acid changes between residues 348 and 450 of ICP8. Construction of a mutant ICP8 gene specifically altered at residues 499 and 502 led to a gene product that was also defective in a nuclear function. Thus, at least part of the region of ICP8 from residues 348 to 450 is required for DNA binding by ICP8. This portion of the protein may be involved in binding to DNA or forming intermolecular contacts needed for cooperative DNA binding. If this region is directly involved in binding of the protein to DNA, the most likely structure predicted for this region involves folding of beta-strands to form a channel for binding to a nucleotide chain.

Characterization of the guinea pig cytomegalovirus genome by molecular cloning and physical mapping

Fragments of guinea pig cytomegalovirus (GPCMV) DNA produced by HindIII or EcoRI restriction endonuclease digestion were cloned into vectors pBR322 and pACYC184, and recombinant fragments representing ca. 97% of the genome were constructed. Hybridization of 32P-labeled cloned and gel-purified HindIII, EcoRI, and XbaI fragments to Southern blots of HindIII-, EcoRI-, and XbaI-cleaved GPCMV DNA verified the viral origin of cloned fragments and allowed construction of HindIII, EcoRI, and XbaI restriction maps. On the basis of the cloning and mapping experiments, the size of GPCMV DNA was calculated to include 239 kilobase pairs, corresponding to a molecular weight of 158 X 10(6). No cross-hybridization between any internal fragments was seen. We conclude that the GPCMV genome consists of a long unique sequence with terminal repeat sequences but without internal repeat regions. In addition, GPCMV DNA molecules exist in two forms. In the predominant form, the molecules demonstrate sequence homology between the terminal fragments; in the minor population, one terminal fragment is smaller by 0.7 X 10(6) daltons and is not homologous with the fragment at the other end of the physical map. The structural organization of GPCMV DNA is unique for a herpesvirus DNA, similar in its simplicity to the structure reported for murine cytomegalovirus DNA and quite dissimilar from that of human cytomegalovirus DNA.

Characterization of guinea pig cytomegalovirus DNA

The genome of guinea pig cytomegalovirus (GPCMV) was analyzed and compared with that of human cytomegalovirus (HCMV). GPCMV and HCMV DNAs were isolated from virions and further purified by CsCl centrifugation. Purified GPCMV DNA sedimented as a single peak in a neutral sucrose gradient and was infectious when transfected into guinea pig embryo fibroblast cells. The cytopathology was characteristic of that seen after infection with GPCMV. Virus DNA purified from virions isolated from infected GPEF or 104C1 cells had a CsCl buoyant density of 1.713 g/cm3, which corresponds to a guanine plus cytosine content of 54.1%. The CsCl buoyant density of GPCMV DNA was slightly less than that of HCMV DNA (1.716 g/cm3), but sufficiently different so that the two virus DNA peaks did not coincide. GPCMV DNA cosedimented with T4 DNA in a neutral sucrose gradient. Restriction endonuclease cleavage of GPCMV or HCMV DNAs with HindIII, XbaI, or EcoRI yielded fragments easily separable by agarose gel electrophoresis and ranging from 1.0 X 10(6) to 25.8 X 10(6) daltons. The number, size, and molarity of GPCMV DNA fragments generated by restriction enzymes were determined. Hybridization of restriction endonuclease-cleaved GPCMV DNA with radioactively labeled HCMV DNA and, conversely, hybridization of restriction endonuclease-cleaved HCMV DNA with radioactively labeled GPCMV DNA indicated sequence homology between the two virus DNAs.