Читать книгу Principles of Virology - Jane Flint, S. Jane Flint - Страница 29

Because viruses are dependent on their hosts for propagation, studies that focus on viral reprogramming of cellular mechanisms have provided unique insights into genetics, cellular biology, and functioning of host defenses. Groundbreaking studies of viruses that infect bacteria (called bacteriophages) in the mid-20th century established the molecular basis of genetic inheritance. Through development and use of stringent, quantitative methods with these relatively simple biological entities, this research confirmed that DNA encodes genes and genes encode proteins. General mechanisms of genetic recombination, repair, and control of gene expression were also elucidated, laying the foundations of modern molecular biology and recombinant DNA technology. Subsequent studies of animal viruses established many fundamental principles of cellular function, including the presence of intervening sequences in eukaryotic genes. The study of cancer (transforming) viruses established the genetic basis of this disease.

With the development of recombinant DNA technology and our increased understanding of viral systems, it has become possible to use viral genomes as vehicles for the delivery of genes to cells and organisms for both scientific and therapeutic purposes. The use of viral vectors to introduce genes into various cells and organisms to study their function has become a standard method in biology. Viral vectors are also being used to treat human disease, for example, via “gene therapy,” in which functional genes delivered by viral vectors compensate for faulty genes in the host cells (Volume II, Chapter 9).

The study of viruses has contributed in a unique way to the field of anthropology. As ancient humans moved from one geographic area to another, the viral strains unique to their original locations came along with them. The presence of such strains can be detected by analysis of viral nucleic acids, proteins, and antibodies from ancient human specimens and in modern populations. Together with archeological information, identification of these virological markers has been used to trace the pathways by which humans came to inhabit various regions of our planet (Fig. 1.2).

Figure 1.2 Tracking ancient human migrations by the viruses they carried. The polyomavirus known as JC virus is transmitted among families and populations and has coevolved with humans since the time of their origin in Africa. This virus produces no disease in normal, healthy people. Most individuals are infected in childhood, after which the virus establishes a persistent infection in the gastrointestinal tract and is shed in urine. Analysis of the genomes of JC virus in human populations from different geographic locations has suggested an expansion of ancient humans from Africa via two distinct migrations, each carrying a different lineage of the virus. Results from these studies are consistent with analyses of human DNAs (shown by the solid line). They also suggest an additional route that was undetectable in the human DNA analyses (indicated by the dashed line). Data from Pavesi A. 2005. J Gen Virol 86:1315–1326.