The Characterization of Varicella-zoster Virus DNA

Section: Resultsmentioning

confidence: 99%

DNA Sequence of the Major Inverted Repeat in the Varicella-Zoster Virus Genome

Davison

Scott

1985

“…A complete description of the relationships between HSV-1 and VZV involves several levels of analysis. One of the more important centres on the effects and possible causes of the striking difference between the base compositions of the two genomes: HSV-1 DNA contains 67% G + C (Becker et al, 1968 ;Kieffet al, 1971), whereas VZV DNA contains 46% G + C (Ludwig et al, 1972). This aspect has been dealt with in some detail elsewhere (McGeoch, 1984;Honess, 1984;.…”

Section: Introductionmentioning

confidence: 99%

Evolutionary Comparisons of the S Segments in the Genomes of Herpes Simplex Virus Type 1 and Varicella-Zoster Virus

Davison

McGeoch

1986

122

SUMMARYThe genomes of herpes simplex virus type 1 (HSV-1) and varicella-zoster virus (VZV) consist of two covalently joined segments, L and S.,Each segment comprises an unique sequence flanked by inverted repeats. We have reported previously the DNA sequences of the S segments in these two genomes, and have identified protein-coding regions therein. In HSV-1, the unique sequence of S contains ten entire genes plus the major parts of two more, and each inverted repeat contains one entire gene; in VZV, the unique sequence of S contains two entire genes plus the major parts of two more, and each inverted repeat contains three entire genes. In this report, an examination of polypeptide sequence homology has shown that each VZV gene has an HSV-1 counterpart, but that six of the HSV-1 genes have no VZV homologues. Thus, although these regions of the two genomes differ in gene layout, they are related to a significant degree. The analysis indicates that the inverted repeats are evidently capable of largescale expansion or contraction during evolution. The differences in gene layout can be understood as resulting from a small number of recombinational events during the descent of HSV-1 and VZV from a common ancestor. INTRODUCTIONMembers of the family Herpesviridae are classified into three subfamilies: the Alpha-, Betaand Gamma-herpesvirinae. This subclassification is based on properties of the virus particle, on features of the replication cycle and on biological aspects, such as host range and site of latency (Matthews, 1982). These criteria have proved useful but, despite some attempts to include genome organization as an additional taxonomical factor, the evidence for relationships between the subfamilies has been circumstantial. Comparisons of currently emerging herpesvirus DNA sequences will allow the relationships to be investigated precisely and directly at the genetic level. For example, recent comparisons of sequences from herpes simplex virus type l (HSV-1) and Epstein-Barr virus, which are members of the Alpha-and Gammaherpesvirinae, respectively, have demonstrated a degree of conservation in the predicted amino acid sequences of at least three virus-coded proteins: the two subunits of the ribonucleotide reductase , the DNA polymerase (Quinn & McGeoch, 1985;Baer et al., 1984) and the major DNA-binding protein (Quinn & McGeoch, 1985). Nevertheless, the available evidence indicates that the Alphaherpesvirinae and Gammaherpesvirinae are rather distantly related. There are as yet no sequence data indicating the degree of relationship between the Betaherpesvirinae and the other subfamilies.In contrast, studies of antigenic relatedness and DNA homology have shown members of the same subfamily to be much more closely related. For example, Davison & Wilkie (1983), using the technique of DNA-DNA hybridization, detected conservation of several genes in five members of the Alphaherpesvirinae. They proposed from the colinear arrangement of conserved

“…The genomes of these viruses are linear double-stranded DNA molecules which contain approximately 46 ~o and 67 ~ guanine plus cytosine respectively (Ludwig et al, 1972;Kieffet al, 1971). Despite this difference, molecular hybridization and DNA sequence studies have revealed that the two viruses have a similar gene arrangement and have allowed functions to be tentatively assigned to a number of VZV gene products which exhibit homology to well studied HSV-1 counterparts (Davison & Wilkie, 1983;McGeoch, 1984;Davison & McGeoch, 1986).…”

Section: Introductionmentioning

confidence: 99%

Identification of a Varicella-Zoster Virus Origin of DNA Replication and Its Activation by Herpes Simplex Virus Type 1 Gene Products

Stow

Davison²

1986

SUMMARYWe have identified and characterized an origin of DNA replication in the genome of the human herpesvirus, varicella-zoster virus (VZV). This origin of replication (VZV ORIs) is located within the major inverted repeats in a position equivalent to that occupied by one of the herpes simplex virus type 1 (HSV-1) replication origins. Products encoded by both VZV and HSV-1 activate cloned copies of VZV ORIs, generating high molecular weight molecules consisting of tandem duplications of the input plasmid. The VZV ORIs region contains a tract of alternating A and T residues located at the centre of symmetry of an almost perfect palindrome of 45 bp, and the use of plasmid deletion mutants has demonstrated that this tract is an important functional element of the origin. Two sequences common to the VZV ORIs region and the regions specifying the two HSV-1 origins (ORIs, located within the TRs/IRs regions, and ORIL, located within the UL region) were identified and these may represent important recognition sites. One is an 11 bp sequence (CGTTCGCACTT), and the other is represented by the tract of alternating A and T residues. VZV does not appear to contain an origin of replication in a position equivalent to that of HSV-10RIL.