Oncogenic viruses

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Among the factors that most significantly contribute to the transformation of protooncogen and in oncogene are some viruses. For the first time these particles located on the border of the living and non-living, opened in 1892, a graduate of St. Petersburg University, Doctor of historical Sciences, Ivanovo.
In 1907, the French researcher A. Borel put forward a hypothesis about the relationship cancer viruses. This dependence was first shown in 1908, when the Danish scientists Ellerman and Bang found in chickens, the causative agent of leukemia can be repeatedly passed through bacterial filters and does not lose his aggressiveness. In 1910 American Peyton rouse has established communication viruses sarcoma chickens. In 1934, his compatriot R. of soup highlighted the virus from tumors of warts, or papillomas, rabbits. In 1936 J.. Bitteren was opened virus breast cancer mice, and 1951 L. gross - leukosis virus of mice, in 1964 Century Arreton - leukosis virus domestic cats, and then the leukosis virus monkeys. In the study of the last great contribution was made by Soviet scientists under the guidance of academician of AMS of the USSR A. B. Lapina. Today there are more than 100 viruses that cause tumors in animals and was called carcinogenic.
The study of viruses leukemia chickens, mice and cats showed a significant chemical and antigenic community, and electron microscopy confirmed the similarity of their structure. In most cases, in natural conditions to cause tumor viruses can only "his" species of animals. The virus leukemia mice does not strike leukocytes cats, and Vice versa. Cats are sick with leukemia, contracted from each other, like we are being infected with influenza a (horizontal transmission). But in mice even prolonged contact with infected animals safe for healthy animals. The spread of the virus is going on from parents to offspring (vertical transmission). In chickens, the disease can be transmitted both through. In 1957, the Soviet researchers (L. A. Zilber with employees and at the same time, I.e. Light-Moldovan employees) proved that the species specificity is not simply a property of the oncoviruses: sarcoma virus chickens may cause cancer and in rats.
Then, in 1958, an outstanding Soviet immunologist and virologist L. A. Zilber formulated the basic concepts of viral theory of cancer. According to her, the virus does not cause destruction of cells, and brings into it the hereditary information that becomes part of the genome of the cells of animals. The infected cell is not converted immediately into cancer, although a number of its biological parameters differs from healthy cells. For carcinogenesis is a need for some activating factor stimulating the multiplication of virus-infected cells. Silber said that the virus "you need special conditions that he showed boleznennostew, and until these conditions do not exist, the virus is harmless". As you can see, in the future, the hypothesis of Zilber factually confirmed, although "starting gun"that gives the signal to accelerated reproduction of infected cells is still not found.
In all living biological objects genetic information stored in DNA, and from there via the process of transcription is passed RNA. Further, during the broadcast of this information is converted for further synthesis of protein in the cytoplasm on ribosomes. Some viruses is the opposite: the genetic information they recorded in RNA, and already in the cell, which became a refuge viruses, during reverse transcription using enzymes (reverse revertaza) building a new DNA. Such viruses are now called retroviruses or RNA viruses.
Among the viruses that cause infectious diseases, there are a DNA virus (smallpox, herpes) and RNA viruses (influenza, rabies, polio, measles). Oncogenic can be and DNA viruses (often the cause tumors in monkeys, fibroma in rabbits), and RNA viruses (breast cancer in mice, viruses leukemia cats and mice, agents sarcoma).
The virus enters only those cells that have him receptors. The sensitivity of the virus to specific molecules of a small group of cells, such as T-helper cells, and only to them amazing. In some cells the virus multiplies in the others. In the cells, allowing the reproduction of the virus, the number of particles increases to tens of millions, and in the end they tear up the cell wall. In other cases, the virus multiplies, as it stuck to cell receptors, then penetrates through the membrane and starts using its molecules information (or matrix) RNA to carry out the synthesis of viral proteins. This does not preclude that the cellular enzymes destroys its own protein shell of the virus, the main thing - if only preserved its nucleic acid.
This latter then firmly embedded in the DNA of cells ("integration" of the virus). Now along with the usual set of proteins that appear on the cell membrane, its DNA gives orders about working out a new antigen of the virus. Another option: viral antigen replaces one of the squirrel tissue compatibility with class I or forces them to socialise and wrong location on the membrane. In any case, the cell must be recognized EC-cells of immune surveillance or T-lymphocytes. But if the viral protein has an immunosuppressive properties, this slight change of the drawing surface transformed virus cells lymphocytes may not notice.