Tetranucleotide Profile of Herpesvirus DNA
Introduction. Herpesvirus DNAs (about 90% of the total genomic sequences of the Herpesvirales family presented in GenBank) contain at a minimum concentration one of the two tetranucleotides, CTAG or TCGA. The “underrepresentation” of CTAG was previously observed only in the DNA of some bacteria and phages. The aim of the study was the further analysis of the formal characteristics of herpesvirus DNA, as well as their comparison with the density of the virus/host DNA microhomology and with the genomic macrostructure of herpes viruses.Materials and methods. Twenty strains and isolates of each of the five types of human herpes viruses (HHV1, HHV2, HHV3, HHV4, HHV5), 10 strains of HHV8, 5 strains of HHV6A, 4 strains of HHV6B and 3 strains of HHV7 were analyzed. GenBank tools were used to determine the frequency of tetranucleotides, and human DNA fragments with size matched herpesvirus DNA were used for comparison.Results. Minimum CTAG concentration in DNA of herpes viruses is mainly characteristic of two- and singlesegment genomes with direct or inverted terminal repeats (classes A,D,E), while the minimum TCGA density is characteristic mainly for DNA that is significantly less structured (classes B,C,F). By increasing CTAG density, human herpes viruses form a sequence close to the sequence of increasing the homology density of 20 nt with human DNA, which also correlates with the macrostructure of DNA. A parallel of this minimization with the DNA structure of herpes viruses or with their belonging to one or another subfamily - as well as the context of the “minimal” CpG (that is, TCGA) - is not noted in the literature. Although herpesvirus DNA is quite large (125- 295 Kb), some of them (for example, HHV4, HHV5 and HHV7 DNA) show noticeable deviations from the second DNA parity rule, and can thus serve as a component of the molecular signature.The Discussion suggests possible hypotheses for the origin of some of the observed phenomena.