Evolution of viruses by acquisition of genes that control nuclear functions in infected cells--an introduction.

The sequencing and deciphering of the human genome provided an insight into the gene complement of the human chromosomes as well as information on the nongenic sequences that constitute the chromosomal DNA molecules. The analyses of the genes and nongenic sequences in the human genome also provided important information on the presence of endogenous retroviruses, retroposons, retrotransposition of genes in the human genome as well as retroduplication of genes and distribution of the duplicated genes in different chromosomes. These issues were discussed in the first Special Issue of Virus Genes on Molecular Evolution of Viruses-Past and Present. In that issue, the discovery of the reverse transcriptase gene in archeabacteria, the retrovirus in drosophilae and endogenous retroviruses in the human genome were discussed. The aim of the present special issue on Molecular Evolution of Viruses is to consider the strategies developed by RNA and DNA viruses to control the nucleus and the nuclear functions in the infected cells.