Characterization of a DNA Topoisomerase Encoded byAmsacta mooreiEntomopoxvirus

Petersen, Birgitte Ø.; Hall, Richard L.; Moyer, Richard W.; Shuman, Stewart

doi:10.1006/viro.1997.8495

Cited by 20 publications

(12 citation statements)

References 36 publications

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“…Similarly, the HaEPV F2L ORF is only 3 kbp from the HaEPV spheroidin gene, while MsEPV homologues of these genes are separated by 70 kbp (175). The MsEPV topoisomerase is adjacent to the vaccinia virus A28L homologue, while in AmEPV these genes are separated by over 100 kbp (143). Thus, the conserved colinear core of genes that has been proposed to exist for EPV genomes (65,175) may in fact be conserved only among the lepidopteran viruses.…”

Section: Continued On Facing Pagementioning

confidence: 99%

The Genome of Melanoplus sanguinipes Entomopoxvirus

Afonso

Tulman

et al. 1999

J Virol

196

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The family Poxviridae contains two subfamilies: theEntomopoxvirinae (poxviruses of insects) and theChordopoxvirinae (poxviruses of vertebrates). Here we present the first characterization of the genome of an entomopoxvirus (EPV) which infects the North American migratory grasshopper Melanoplus sanguinipes and other important orthopteran pests. The 236-kbp M. sanguinipes EPV (MsEPV) genome consists of a central coding region bounded by 7-kbp inverted terminal repeats and contains 267 open reading frames (ORFs), of which 107 exhibit similarity to previously described genes. The presence of genes not previously described in poxviruses, and in some cases in any other known virus, suggests significant viral adaptation to the arthropod host and the external environment. Genes predicting interactions with host cellular mechanisms include homologues of the inhibitor of apoptosis protein, stress response protein phosphatase 2C, extracellular matrixin metalloproteases, ubiquitin, calcium binding EF-hand protein, glycosyltransferase, and a triacylglyceride lipase. MsEPV genes with putative functions in prevention and repair of DNA damage include a complete base excision repair pathway (uracil DNA glycosylase, AP endonuclease, DNA polymerase β, and an NAD+-dependent DNA ligase), a photoreactivation repair pathway (cyclobutane pyrimidine dimer photolyase), a LINE-type reverse transcriptase, and a mutT homologue. The presence of these specific repair pathways may represent viral adaptation for repair of environmentally induced DNA damage. The absence of previously described poxvirus enzymes involved in nucleotide metabolism and the presence of a novel thymidylate synthase homologue suggest that MsEPV is heavily reliant on host cell nucleotide pools and the de novo nucleotide biosynthesis pathway. MsEPV and lepidopteran genus B EPVs lack genome colinearity and exhibit a low level of amino acid identity among homologous genes (20 to 59%), perhaps reflecting a significant evolutionary distance between lepidopteran and orthopteran viruses. Divergence between MsEPV and theChordopoxvirinae is indicated by the presence of only 49 identifiable chordopoxvirus homologues, low-level amino acid identity among these genes (20 to 48%), and the presence in MsEPV of 43 novel ORFs in five gene families. Genes common to both poxvirus subfamilies, which include those encoding enzymes involved in RNA transcription and modification, DNA replication, protein processing, virion assembly, and virion structural proteins, define the genetic core of the Poxviridae.

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Section: Continued On Facing Pagementioning

confidence: 99%

The Genome of Melanoplus sanguinipes Entomopoxvirus

Afonso

Tulman

et al. 1999

J Virol

196

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“…(The Tp2 nucleotide is defined as the ϩ1 nucleotide.) Topoisomerases encoded by other genera of poxviruses recognize the same DNA target sequence (2)(3)(4)(5)(6), despite the large variations in overall G/C contents of the genomes of the different poxvirus genera. Available structural and biochemical studies suggest that the assembly of a catalytically competent topoisomerase active site is triggered by recognition of the 5Ј-CCCTT/3Ј-GGGAA target sequence (7,8).…”

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confidence: 99%

Individual Nucleotide Bases, Not Base Pairs, Are Critical for Triggering Site-specific DNA Cleavage by Vaccinia Topoisomerase

Tian

Sayer

Jerina

et al. 2004

Journal of Biological Chemistry

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Vaccinia DNA topoisomerase forms a covalent DNA-(3-phosphotyrosyl)-enzyme intermediate at a specific target site 5-C ؉5 C ؉4 C ؉3 T ؉2 T ؉1 p2N ؊1 in duplex DNA. Here we study the effects of abasic lesions at individual positions of the scissile and nonscissile strands on the rate of single-turnover DNA transesterification and the cleavage-religation equilibrium. The rate of DNA incision was reduced by factors of 350, 250, 60, and 10 when abasic sites replaced the ؊1N, ؉1T, ؉2T, and ؉4C bases of the scissile strand, but abasic lesions at ؉5C and ؉3C had little or no effect. Abasic lesions in the nonscissile strand in lieu of ؉4G, ؉3G, ؉2A, and ؉1A reduced the rate of cleavage by factors of 130, 150, 10, and 5, whereas abasic lesions at ؉5G and ؊1N had no effect. The striking positional asymmetry of abasic interference on the scissile and nonscissile strands highlights the importance of individual bases, not base pairs, in promoting DNA cleavage. The rate of single-turnover DNA religation by the covalent topoisomerase-DNA complex was insensitive to abasic sites within the CCCTT sequence of the scissile strand, but an abasic lesion at the 5-OH nucleoside (؊1N) of the attacking DNA strand slowed the rate of religation by a factor of 600. Nonscissile strand abasic lesions at ؉1A and ؊1N slowed the rate of religation by factors of ϳ140 and 20, respectively, and strongly skewed the cleavage-religation equilibrium toward the covalent complex. Thus, abasic lesions immediately flanking the cleavage site act as topoisomerase poisons.Poxvirus topoisomerases are exemplary type IB topoisomerase family members; they cleave and rejoin one strand of the DNA duplex through a transient DNA-(3Ј-phosphotyrosyl)-enzyme intermediate. Vaccinia topoisomerase cleaves duplex DNA at a pentapyrimidine target sequence, 5Ј-(T/C)CCTTp2 (1). (The Tp2 nucleotide is defined as the ϩ1 nucleotide.) Topoisomerases encoded by other genera of poxviruses recognize the same DNA target sequence (2-6), despite the large variations in overall G/C contents of the genomes of the different poxvirus genera. Available structural and biochemical studies suggest that the assembly of a catalytically competent topoisomerase active site is triggered by recognition of the 5Ј-CCCTT/3Ј-GGGAA target sequence (7,8).Early studies using nuclease footprinting, modification interference, modification protection, analog substitution, and UV cross-linking techniques suggested that vaccinia topoisomerase makes contact with several nucleotide bases and the sugar-phosphate backbone of DNA within and immediately flanking the CCCTT element (9 -15). Recent studies have focused on delineating the features of the DNA interface that affect the kinetics of transesterification. For example, positionspecific covalent polycyclic aromatic hydrocarbon diol epoxide-DNA adducts have been exploited to probe the minor groove interface (16) and the effects of intercalation at all of the dinucleotides steps spanning the target site (17, 18). The aromatic hydrocarbon adduct studies delineated the ...

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“…All the poxviruses studied to date encode a topoisomerase (6,10,12,23). In the case of vaccinia virus topoisomerase, the most thoroughly studied model, it has been shown that replication requires topoisomerase function (29).…”

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Molluscum Contagiosum Virus Topoisomerase: Purification, Activities, and Response to Inhibitors

Hwang

Wang

Bushman

1998

J Virol

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Molluscum contagiosum virus (MCV), the only member of theMolluscipoxvirus genus, causes benign papules in healthy people but disfiguring lesions in immunocompromised patients. The sequence of MCV has been completed, revealing that MCV encodes a probable type I topoisomerase enzyme. All poxviruses sequenced to date also encode type I topoisomerases, and in the case of vaccinia virus the topoisomerase has been shown to be essential for replication. Thus, inhibitors of the MCV topoisomerase might be useful as antiviral agents. We have cloned the gene for MCV topoisomerase, overexpressed and purified the protein, and begun to characterize its activities in vitro. Like other eukaryotic type I topoisomerases, MCV topoisomerase can relax both positive and negative supercoils. An analysis of the cleavage of plasmid and oligonucleotide substrates indicates that cleavage by MCV topoisomerase is favored just 3′ of the sequence 5′ (T/C)CCTT 3′, resulting in formation of a covalent bond to the 3′ T residue, as with other poxvirus topoisomerases. We identified solution conditions favorable for activity and measured the rate of formation and decay of the covalent intermediate. MCV topoisomerase is sensitive to inhibition by coumermycin A1 (50% inhibitory concentration, 32 μM) but insensitive to five other previously reported topoisomerase inhibitors. This work provides the point of departure for studies of the mechanism of function of MCV topoisomerase and the development of medically useful inhibitors.

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Characterization of a DNA Topoisomerase Encoded byAmsacta mooreiEntomopoxvirus

Cited by 20 publications

References 36 publications

The Genome of Melanoplus sanguinipes Entomopoxvirus

The Genome of Melanoplus sanguinipes Entomopoxvirus

Individual Nucleotide Bases, Not Base Pairs, Are Critical for Triggering Site-specific DNA Cleavage by Vaccinia Topoisomerase

Molluscum Contagiosum Virus Topoisomerase: Purification, Activities, and Response to Inhibitors

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