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N A Petrov

Publications and source records attributed to N A Petrov.

At least 19 recordsLinked to original sources
PubMed2002

Analysis of the monkeypox virus genome.

Monkeypox virus (MPV) belongs to the orthopoxvirus genus of the family Poxviridae, is endemic in parts of Africa, and causes a human disease that resembles smallpox. The 196,858-bp MPV genome was analyzed with regard to structural features and open reading frames. Each end of the genome contains an identical but oppositely oriented 6379-bp terminal inverted repetition, which similar to that of other orthopoxviruses, includes a putative telomere resolution sequence and short tandem repeats. Computer-assisted analysis was used to identify 190 open reading frames containing >/=60 amino acid residues. Of these, four were present within the inverted terminal repetition. MPV contained the known essential orthopoxvirus genes but only a subset of the putative immunomodulatory and host range genes. Sequence comparisons confirmed the assignment of MPV as a distinct species of orthopoxvirus that is not a direct ancestor or a direct descendent of variola virus, the causative agent of smallpox.

Animals↗
PubMed2001

Human monkeypox and smallpox viruses: genomic comparison.

Monkeypox virus (MPV) causes a human disease which resembles smallpox but with a lower person-to-person transmission rate. To determine the genetic relationship between the orthopoxviruses causing these two diseases, we sequenced the 197-kb genome of MPV isolated from a patient during a large human monkeypox outbreak in Zaire in 1996. The nucleotide sequence within the central region of the MPV genome, which encodes essential enzymes and structural proteins, was 96.3% identical with that of variola (smallpox) virus (VAR). In contrast, there were considerable differences between MPV and VAR in the regions encoding virulence and host-range factors near the ends of the genome. Our data indicate that MPV is not the direct ancestor of VAR and is unlikely to naturally acquire all properties of VAR.

Amino Acid Sequence↗
PubMed2001

[Individual variability in the karytype of Chironomus plumosus: atypical puffs in larva from a natural population from the Chita region].

Atypical puffing of polytene chromosomes of Chironomus plumosus (1 larvae, IV stage) from the Ivan lake in Chita region, southern part of Siberia, has been described. At the sites of ordinary localization of interdisks and puff-patterns typical of Ch. plumosus the puffs in our material displayed different levels of activity: from a light vacuolous spot to puffs of class 5. Most of these puffs were revealed in Ch. plumosus for the first time, namely, puffs IA10a-r, IB12v-y + 13a-d, IIC14p-z + 15a-z + 16a-e, IIC14p-z + 15a-h, IID14a-m + 13s-w, IID11-2a-d, IID1p-x + 2a-d, IIIE3g-a and IIIF13h-p + 14a-e. Some other puffs, such as IB16a-k, IB15m-r + 16a-m, IB21a-o, IIC20, IVG6 and IVG7, were described earlier (Maksimova, 1979, 1983). The majority of observed puffs turned out to be heterozygous. Only one puff-knob, IIIE3g-a of class 5 activity, was found in all cells of the studied salivary glands. Its origin may be due to the appearance of heterozygoous inversion pluE1.2. All other puffs were observed in some part of cells. It is supposed that the appearance of larvae with unusually high functional activity of chromosomes may be presumably induced by stress influence of certain environmental factors.

Animals↗
PubMed1999

Effect of base analog substitutions in the specific GATC site on binding and methylation of oligonucleotide duplexes by the bacteriophage T4 Dam DNA-[N6-adenine] methyltransferase.

The interaction of the phage T4 Dam DNA-[N6-adenine] methyltransferase with 24mer synthetic oligonucleotide duplexes having different purine base substitutions in the palindromic recognition sequence, GATC, was investigated by means of gel shift and methyl transfer assays. The substitutions were introduced in either the upper or lower strand: guanine by 7-deazaguanine (G-->D) or 2-aminopurine (G-->N) and target adenine by purine (A-->P) or 2-aminopurine (A-->N). The effects of each base modification on binding/methylation were approximately equivalent for both strands. G-->D and G-->N substitutions resulted in a sharp decrease in binary complex formation. This suggests that T4 Dam makes hydrogen bonds with either the N7- or O6-keto groups (or both) in forming the complex. In contrast, A-->P and A-->N substitutions were much more tolerant for complex formation. This confirms our earlier observations that the presence of intact 5'-G:C base pairs at both ends of the methylation site is critical, but that base substitutions within the central A:T base pairs show less inhibition of complex formation. Addition of T4 Dam to a complete substrate mixture resulted in a burst of [3H]methylated product. In all cases the substrate dependencies of bursts and methylation rates were proportional to each other. For the perfect 24mer k cat = 0.014/s and K m = 7.7 nM was obtained. In contrast to binary complex formation the two guanine substitutions exerted relatively minor effects on catalytic turnover (the k cat was reduced at most 2. 5-fold), while the two adenine substitutions showed stronger effects (5- to 15-fold reduction in k cat). The effects of base analog substitutions on K m(DNA) were more variable: A-->P (decreased); A-->N and G-->D (unchanged); G-->N (increased).

2-Aminopurine↗
PubMed1998

The genomic sequence analysis of the left and right species-specific terminal region of a cowpox virus strain reveals unique sequences and a cluster of intact ORFs for immunomodulatory and host range proteins.

Sequencing and computer analysis of the left (52,283 bp) and right (49,649 bp) variable DNA regions of the cowpox virus strain GRI-90 (CPV-GRI) has revealed 51 and 37 potential open reading frames (ORFs), respectively. Comparison of the structure-function organization of these DNA regions of CPV-GRI with those previously published for corresponding regions of genomes of vaccinia virus, strains Copenhagen (VAC-COP) and Western Reserve (VAC-WR); and variola major virus, strains India-1967 (VAR-IND), Bangladesh-1975 (VAR-BSH); and alastrim variola minor virus, strain Garcia-1966 (VAR-GAR), was performed. Within the left terminal region under study, an extended DNA sequence (14,171 bp), unique to CPV, has been found. Within the right region of the CPV-GRI genome two segments, which are unique to CPV DNA (1579 and 3585 bp) have been found. Numerous differences have been revealed in the genetic structure of CPV-GRI DNA regions, homologous to fragments of the genomes of the above-mentioned orthopoxvirus strains. A cluster of ORFs with structural similarity ot immunomodulatory and host range function of other poxviruses have also been detected. A comparison of the sequences of ORF B, crmA, crmB, crmC, IMP, and CHO hr genes of CPV Brighton strain (CPV-BRI) with the corresponding genes in strain GRI-90 have revealed an identity at the amino acid level ranging from 82 to 96% between the two strains. The findings are significant in light of the recent demonstration of CPV as an important poxvirus model system to probe the precise in vivo role(s) of the unique virally encoded immunomodulatory proteins. Also, the presence of a complete and intact repertoire of immunomodulatory proteins, ring canal proteins family, and host range genes indicates that CPV may have been the most ancient of all studied orthopoxviruses.

Amino Acid Sequence↗
PubMed1997

Interaction of the phage T4 Dam DNA-[N6-adenine] methyltransferase with oligonucleotides containing native or modified (defective) recognition sites.

The DNA-[N 6-adenine]-methyltransferase (Dam MTase) of phage T4 catalyzes methyl group transfer from S-adenosyl-l-methionine (AdoMet) to the N6-position of adenine in the palindromic sequence, GATC. We have used a gel shift assay to monitor complex formation between T4 Dam and various synthetic duplex oligonucleotides, either native or modified/defective. The results are summarized as follows. (i) T4 Dam bound with approximately 100-fold higher affinity to a 20mer specific (GATC-containing) duplex containing the canonical palindromic methylation sequence, GATC, than to a non-specific duplex containing another palindrome, GTAC. (ii) Compared with the unmethylated duplex, the hemimethylated 20mer specific duplex had a slightly increased ( approximately 2-fold) ability to form complexes with T4 Dam. (iii) No stable complex was formed with a synthetic 12mer specific (GATC-containing) duplex, although T4 Dam can methylate it. This indicates that there is no relation between formation of a catalytically competent 12mer-Dam complex and one stable to gel electrophoresis. (iv) Formation of a stable complex did not require that both strands be contiguous or completely complementary. Absence of a single internucleotide phosphate strongly reduced complex formation only when missing between the T and C residues. This suggests that if T4 Dam makes critical contact(s) with a backbone phosphate(s), then the one between T and C is the only likely candidate. Having only one half of the recognition site intact on one strand was sufficient for stable complex formation provided that the 5'G.C base-pairs be present at both ends of the palindromic, GATC. Since absence of either a G or C abolished T4 Dam binding, we conclude that both strands are recognized by T4 Dam.

Bacteriophage T4↗
PubMed1990

[Modern variations of human influenza group A viruses at the molecular level].

The authors own results on the variety of the genomic primary structures in human influenza A viruses participating in the epidemic process, including the atypical viruses. The comparative studies revealed new trends in the HA gene antigenic drift on the late stages and the PB1 gene shift. Modifications occurring in the primary structure of the influenza A viruses native genomes during laboratory treatment (adaptation to new hosts, vaccine preparation, egg passaging) have been analyzed. Sequencing of several types of "antigenic anachronisms" revealed the direct links between some of such viruses and the anthropogenic pollution of the biosphere by vaccine strains. Modifications in the HA genes of influenza A viruses during the persistent infection have also been studied.

Amino Acid Sequence↗
PubMed1990

Primary structure of the gene coding for the haemagglutinin of influenza virus A/Leningrad/385/80(H3N2): detection of a point mutation responsible for the antigenic drift.

Primary structure of the gene coding for haemagglutinin (HA-gene) of influenza virus A/Leningrad/385/80(H2N2) isolated during the epidemics of influenza in Leningrad in 1980 was determined. The close relationship of HA gene of this virus to the corresponding gene of the virus A/Bangkok/1/79(H3N2) was confirmed. It was shown that a single mutation in an antigenic site (the change from isoleucine to leucine at position 51 of HA1 gene) caused an antigenic drift. One silent mutation was detected (nucleotide 428 of HA1 gene) which points at the relatedness of strains A/Leningrad/385/80 with A/Bangkok/2/79 and with other more recent strains. These data allowed to determine the position of the strain A/Leningrad/385/80 HA gene regarding to the evolutionary relationships of HA genes of influenza A (H3N2 subtype) viruses. The branch leading to the above-mentioned strain is supposed to start from a point common for strains isolated following A/Bangkok/1/79. The mutations of HA genes presented in this subgroup were analysed supporting the notion on limited evolutionary potential of the subtype H3N2 influenza viruses.

Amino Acid Sequence↗
PubMed1988

[Changes in the amino acid sequence of hemagglutinin during sequential adaptation of human influenza virus A to replication in mice].

The primary structure of hemagglutinin (HA) gene of Influenza virus A/USSR/90/77 (H1N1) variants after 3 and 11 passages has been determined. In the HA1 coding region of mice-adapted virus (11 passages) there are two amino acid substitutions: Thr 89----Ala and Asn 127----Asp. At the first stage of adaptation (3-rd passage) only a single mutation was detected: Asn 127----Asp. The adaptation is accompanied by the loss of specific carbohydrate attachment sites adjacent to the receptor-binding site located at HA1 subunit with a concomitant variation in antigenicity.

Adaptation, Biological↗