6,502
edits
Changes
Jump to navigation
Jump to search
Feline Immunodeficiency Virus (view source)
Revision as of 12:21, 27 August 2010
, 12:21, 27 August 2010→Agent
Line 8:
Line 8:
+ * The conversion of ssRNA to ssDNA, mediated by the viral enzyme reverse transcriptase, results in a dsDNA molecule longer than that of the original genome. This dsDNA migrates to the nucleus where it is ultimately integrated into the host chromosome by the viral enzyme integrase.
− * Once integrated into the host genome, the viral dsDNA is referred to as a provirus. The provirus remains latent until "triggered" into transcription of mRNA by host cell machinery.
− * Viral mRNA transcription of the provirus is mediated by cellular RNA polymerase II.
− * The new virions are released by budding, which does not always result in cell lysis.
− * There is a high mutation rate, as reverse transcription is an error-prone process. Thus, retroviruses usually present a high genetic diversity.
==Agent==
==Agent==
−FIV is a member of the lentivirus genus of the Retroviridae family. The Retroviridae are enveloped viruses which contain a single-stranded RNA genome within an icosahedral nucleocapsid. Glycoprotein surface spikes are located on the envelope. Unusually, Retroviruses have a diplod genome: two identical copies of their positive-sense ssRNA are found on the virion<sup>viro</sup>. During viral replication, reverse transcriptase converts the ssRNA genome to ssDNA. A dsDNA can then be made from the ssDNA template. This provirus DNA then becomes integrated into the host genome, where it serves as a template for the production of progeny ssRNA genomes and messenger RNA. The host cell's transcription mechanisms perform these tasks.
+FIV is a member of the lentivirus genus of the Retroviridae family. The Retroviridae are enveloped viruses which contain a single-stranded RNA genome within an icosahedral nucleocapsid. Glycoprotein surface spikes are located on the envelope. Unusually, Retroviruses have a diplod genome: two identical copies of their positive-sense ssRNA are found on the virion<sup>viro</sup>. During viral replication, reverse transcriptase converts the ssRNA genome to ssDNA. This process is inherently error-prone, and the high rate of mutation gives rise to a wide genetic diversity of virus<sup>viro</sup>. A dsDNA can then be made from the ssDNA template. This provirus DNA then becomes integrated into the host genome by the actions of the viral enzyme integrase, and remains latent until transcription is initiated by the host cell machinery<sup>viro</sup>. Proviral DNA then serves as a template for the production of progeny ssRNA genomes and messenger RNA.
Once the proviral DNA has been transcribe and translated, the virions assemble and are release by budding through the host cell membrane. This does not always cause lysis<sup>viro</sup>.
+
+
− * Many retroviruses carry oncogenes (e.g., Rous sarcoma virus in chickens), while others do not (e.g., human T-cell lymphotrophic virus). However, some retroviruses may cause tumors without carrying oncogenes.
* Many retroviruses carry oncogenes (e.g., Rous sarcoma virus in chickens), while others do not (e.g., human T-cell lymphotrophic virus). However, some retroviruses may cause tumors without carrying oncogenes.
* All retroviral genomes consist of two molecules of ssRNA, (+)sense, have 5' cap and 3' poly-(A) (equivalent to mRNA) and four characteristic coding regions (gag-pro-pol-env). Gag (group specific antigen: matrix protein, nucleoprotein, capsid) genes; pro (protease) gene; pol (reverse transcriptase and RNase-H); and env (envelope, receptor binding) genes (see Fig.15.2). These vary in size from ~8-11 kb. They are the only viruses that are truly diploid. Additionally, there is a specific type of cellular transporter RNA (tRNA) (usually trp, pro or lys) - required for replication that is present in the virion.
* All retroviral genomes consist of two molecules of ssRNA, (+)sense, have 5' cap and 3' poly-(A) (equivalent to mRNA) and four characteristic coding regions (gag-pro-pol-env). Gag (group specific antigen: matrix protein, nucleoprotein, capsid) genes; pro (protease) gene; pol (reverse transcriptase and RNase-H); and env (envelope, receptor binding) genes (see Fig.15.2). These vary in size from ~8-11 kb. They are the only viruses that are truly diploid. Additionally, there is a specific type of cellular transporter RNA (tRNA) (usually trp, pro or lys) - required for replication that is present in the virion.