Рous саркома вирусы: құрамы, қасиеттері және жұқтыру механизмі

Species of virus

Rous sarcoma virus (RSV) (/r//aʊ//s/) is a retrovirus and is the first oncovirus to have been described. It causes sarcoma in chickens. As with all retroviruses, it reverse transcribes its RNA genome into cDNA before integration into the host DNA.

The src gene is oncogenic as it triggers uncontrolled growth in abnormal host cells. It was the first retroviral oncogene to be discovered. It is an acquired gene, found to be present throughout the animal kingdom with high levels of conservation between species. The chicken src gene was taken up by RSV and incorporated into its genome. The v Src gene is thought to confer the virus with the advantage of being able to stimulate uncontrolled mitosis of host cells, providing abundant cells for fresh infection. The src gene is not essential for RSV reproduction but it greatly increases virulence when present. This element has been shown to prevent the degradation of the unspliced viral RNA. Other elements that have been identified in RSV include a primer binding site.

Gag proteins are necessary for virion assembly and mature virus infection of the host cell. The gag protein (Pr76) for RSV contains 701 amino acids. It is cleaved by virus encoded protease, releasing products found in the infectious virion. These cleaved products include the matrix (MA), capsid (CA), and nucleocapsid (NC), which are able to enter other pathways to infect new cells.

RSV has an envelope which has one glycoprotein: env. Env is made up of gp85 and gp37, which are glycoproteins that assemble into oligomers. The function of env is to bind RSV to the host cell receptor and induce fusion with the target cell in a pH independent manner. The envelope is acquired during exocytosis. The virus buds or pushes on the plasma membrane, which allows it to leave the cell with a new outer membrane from the host cell.

There are two ways viruses can enter the host cell: cell receptor endocytosis or fusion. Fusion occurs when the virus fuses together with the target cell membrane and releases its genome into the cell. RSV enters the host cell through fusion of the host cell membrane.

In order for the RSV genome transcription to occur, a primer is required. 4S RNA is the primer for RSV and 70S RNA serves as the template for DNA synthesis. Reverse transcriptase, an RNA dependent DNA polymerase, transcribes viral RNA into the full length DNA complement.