Human JC Polyomavirus: Difference between revisions
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Interesting features of cell structure; how it gains energy; what important molecules it produces. | Interesting features of cell structure; how it gains energy; what important molecules it produces. | ||
==Ecology== | ==Ecology and Pathology== | ||
JC virus exposure and infection usually occurs at an early age in humans. The infection is widespread it is estimated that 50-80% of adults have antibodies to the JC virus indicating the exposure and/or presence of the JC virus. Transmission of the virus is still not completely understood but evidence of respiratory transmission had been found. Alternative modes of transmission are still being researched. (2) | |||
Persistent infections occur in the cells of the kidneys and of the urinary tract in healthy individuals. The immune system in healthy individuals is able to clear infection causing the virus to establish latent infections. | |||
In active infection, viral DNA replication can undergo transformation. The T antigens are the viral proteins responsible for the transformation. Infected cells carry the virus containing transformed DNA to the brain. Once the virus reaches the oligodendrocytes in the brain, a highly productive infection is initiated. (3.) | |||
Active infections occur when the JC virus becomes reactivated in permissive cells of immunosuppressed individuals that have a decrease in the amount of immune system cells, especially the CD34+ cells. AIDS is a major cause of reactivation of the JC virus. JC virus enters into a lytic active infection of the oligodendrocyte glial cells in the brain. These cells are the myelin producing cells of the brain. The infection causes dymyelination of these cells leading to lesions. and loss of brain function.(7.) | |||
PML results from this infection, and is a fatal disease. PML first, evolves slowly, and the loss of brain functions occurs at a similar rate. Impairment in vision and speech and often movement start to occur. Once PML starts to progress rapidly these symptoms become more severe leading to blindness and paralyzation and eventually coma and death.(5.) The life expectancy of a patient with PML is between several months and 1 year depending on the severity of the immune system deficiency. Additional from predisposing immune disorders, liver and heart transplant have also been linked to the onset of PML. | |||
In active infection, viral DNA replication can undergo transformation. The T antigens are the viral proteins responsible for the transformation. Infected cells carry the virus containing transformed DNA to the brain. Once the virus reaches the oligodendrocytes in the brain, a highly productive infection is initiated. (7.) | |||
==Current Research== | ==Current Research== | ||
Revision as of 17:38, 17 December 2008
A Microbial Biorealm page on the genus Human JC Polyomavirus
Classification
Higher order taxa
Viruses; dsDNA viruses, no RNA stage; Polyomaviridae; Polyomavirus
Species
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NCBI: Taxonomy |
JC virus
Description and significance
The JC virus was first isolated from a brain in a patient with Hodgkin’s disease in 1971. The patient was also suffering from Progressive multifocal leaukoencephalopathy (PML). The virus is named after the patient’s initials. The JC virus is a double-stranded DNA virus with a very small genome. It is strictly a human virus whose viral chromosome structure is very similar to its host chromatin.#5 JC virus have a very simple genome. Inside its human host it can establish three kinds of infections: latent, persistent, and active infections. The infections are established depending on the strength of the host’s immune system, and the tissue type that is infected. (7.). Latent infections occur in the kidney tissue. Persistent infections occur in renal proximal tubule cells, and active infections occur in the oligodendrocyte glial cells in the central nervous system. (8.) These cells specifically support replication of the virus. Active infections destroy oligodendrocytes and lead to a disease known as Progressive multifocal leaukoencephalopathy (PML). (7.) The JC virus infection is extremely widespread, and currently there no cure for when the virus become active.
Genome structure
The JC virus genome consists of a single double stranded DNA molecule. Their DNA is a covalently closed, superhelical, circular molecule and assembled in a set of about 21 nucleosomes. #5. There are four cellular histones associated with the DNA. H2A, H2B, H3, and H4 cellular histone are in the form of chromatin. They control transcription after infection. Two copies of each histone are contained within each of the 21 nucleosomes. The genome consists of 5.130 nucleotide pairs long.(1.) The circular molecule contains an early transcription unit region and a late transcription unit region and a non-coding region. The non-coding region is the viral regulatory region and includes an origin of replication, that both regions are initiated by, and bidirectional promoters and enhancers that control transcription. (9.)
The two transcription units code for a total of six genes in the genome. The early transcription unit extends from the origin to half way around the circular genome (Book)and encodes alternatively spliced transforming proteins. These proteins are large T antigens and small t antigens. They are considered the viral regulatory proteins and share common N-terminal sequences but have different C-terminal sequences. The late transcription unit encodes the three structural capsid proteins, VP1 major capsid protein and minor capsid proteins VP2 and VP3. The coding sequences of VP2 and Vp3 overlap with the entire sequence of the VP3 contained within the VP2’s C-terminus. The N-terminus of VP1 overlaps with VP2 and VP3 at their C-terminus.It consists of alternately spliced mRNAs. (9.) It also encodes in its leader region a small late protein called the agnoprotein that functions in the transporting of the capsid proteins to the nucleus.
Cell structure and metabolism
Interesting features of cell structure; how it gains energy; what important molecules it produces.
Ecology and Pathology
JC virus exposure and infection usually occurs at an early age in humans. The infection is widespread it is estimated that 50-80% of adults have antibodies to the JC virus indicating the exposure and/or presence of the JC virus. Transmission of the virus is still not completely understood but evidence of respiratory transmission had been found. Alternative modes of transmission are still being researched. (2)
Persistent infections occur in the cells of the kidneys and of the urinary tract in healthy individuals. The immune system in healthy individuals is able to clear infection causing the virus to establish latent infections. In active infection, viral DNA replication can undergo transformation. The T antigens are the viral proteins responsible for the transformation. Infected cells carry the virus containing transformed DNA to the brain. Once the virus reaches the oligodendrocytes in the brain, a highly productive infection is initiated. (3.) Active infections occur when the JC virus becomes reactivated in permissive cells of immunosuppressed individuals that have a decrease in the amount of immune system cells, especially the CD34+ cells. AIDS is a major cause of reactivation of the JC virus. JC virus enters into a lytic active infection of the oligodendrocyte glial cells in the brain. These cells are the myelin producing cells of the brain. The infection causes dymyelination of these cells leading to lesions. and loss of brain function.(7.)
PML results from this infection, and is a fatal disease. PML first, evolves slowly, and the loss of brain functions occurs at a similar rate. Impairment in vision and speech and often movement start to occur. Once PML starts to progress rapidly these symptoms become more severe leading to blindness and paralyzation and eventually coma and death.(5.) The life expectancy of a patient with PML is between several months and 1 year depending on the severity of the immune system deficiency. Additional from predisposing immune disorders, liver and heart transplant have also been linked to the onset of PML. In active infection, viral DNA replication can undergo transformation. The T antigens are the viral proteins responsible for the transformation. Infected cells carry the virus containing transformed DNA to the brain. Once the virus reaches the oligodendrocytes in the brain, a highly productive infection is initiated. (7.)
Current Research
Enter summarries of the most rescent research here--at least three required
References
Edited by student of Emily Lilly at University of Massachusetts Dartmouth.
