Mason pfizer monkey virus: Difference between revisions
| Line 46: | Line 46: | ||
By itself, genomic nucleic acid of MPMV is not infectious. Viral protease activity is strictly limited to the completion of the viral budding process (Parker and Hunter, 2001). | By itself, genomic nucleic acid of MPMV is not infectious. Viral protease activity is strictly limited to the completion of the viral budding process (Parker and Hunter, 2001). | ||
Reverse transcriptases (RTs) catalyze the conversion of single-stranded RNA into double-stranded viral DNA for integration into host chromosomes. Proteins in this subfamily contain long terminal repeats (LTRs) and are multifunctional enzymes with RNA-directed DNA polymerase, DNA directed DNA polymerase, and ribonuclease hybrid (RNase H) activities. The viral RNA genome enters the cytoplasm as part of a nucleoprotein complex, and the process of reverse transcription generates in the cytoplasm forming a linear DNA duplex via an intricate series of steps. This duplex DNA is colinear with its RNA template, but contains terminal duplications known as LTRs that are not present in viral RNA. It has been proposed that two specialized template switches, known as strand-transfer reactions or "jumps", are required to generate the LTRs PMID 9831551. | Reverse transcriptases (RTs) catalyze the conversion of single-stranded RNA into double-stranded viral DNA for integration into host chromosomes. Proteins in this subfamily contain long terminal repeats (LTRs) and are multifunctional enzymes with RNA-directed DNA polymerase, DNA directed DNA polymerase, and ribonuclease hybrid (RNase H) activities. The viral RNA genome enters the cytoplasm as part of a nucleoprotein complex, and the process of reverse transcription generates in the cytoplasm forming a linear DNA duplex via an intricate series of steps. This duplex DNA is colinear with its RNA template, but contains terminal duplications known as LTRs that are not present in viral RNA. It has been proposed that two specialized template switches, known as strand-transfer reactions or "jumps", are required to generate the LTRs PMID 9831551. | ||
Revision as of 04:42, 18 December 2008
A Microbial Biorealm page on the genus Mason pfizer monkey virus
ICTV Classification
Higher order taxa
Viruses; Retro-transcribing viruses; Retroviridae; Orthoretrovirinae; Betaretrovirus NCBI
Species
Genus species: Mason Pfizer Monkey Virus
|
NCBI: Taxonomy |
Description and significance
Mason Pfizer Monkey virus (MPMV)is a simian retrovirus (SRV)and is the most thoroughly understood of the D-type Betaretrovirus. MPMV is the prototype for the D-type retroviruses. The fundamental assembly steps (Gag particle formation, transport to the membrane, membrane interaction/viral budding, and viral release) are separate sequential processes allowing this virus to serve as an important model of retroviral assembly (Parker and Hunter, 2001). MPMV was first observed by Harish C. Chopra and Marcus M. Mason in 1970 from a spontaneous breast adenocarcinoma in an 8-year old rhesus monkey (Macaca mulatta)that had been in estrus for approximately one year(Chopra and Mason, 1970). MPMV has properties similar to the C-type and B-type viruses, but is morphologically distinct (Fine and Schochetman, 1978). MPMV is distinguished by accumulation of A-type intracellular particles in the cytoplasm and budding release to acquire viral protease activity. MPMV is pathogenic in Old World monkeys, Family Cercopithecidae(Fine and Schochetman, 1978) and causes immunodeficiency syndrome (Bohl et al., 2005) and tumors (Heras et al., 1991).
Initially the classification of the virus was induction of simian AIDS (SAIDS) however, SRV's are unrelated to simian immunodeficiency virus (SIV's), which is currently recognized as the simian counterpart of the human immunodeficiency virus (Conte et al., 1997). - EXPAND ON THIS IF YOU WANT LATER
Genome structure
MPMV genome is dimeric; not segmented, and consists of a single molecule of linear, positive-sense, single-stranded RNA. The genome has been fully sequenced and the complete genome is of one monomer of 8,557 nucleotides in length. The genome has terminally redundant sequences that have long terminal repeats (LTR) of about 350 nucleotides. The 5'–end of the genome has a methylated nucleotide cap; cap sequence is of type 1 m7G5ppp5'GmpNp. The 3'–terminus of each monomer has a poly (A) tract, a tRNA–like structure, and accepts lysin. http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/
The genome contains four protein coding genes, and two non protein coding genes. gag-pro-pol-env genes (MPMVgp1) code for protein products: Pr95, DU, RT-IN, gp70 SU, gp20 TM, and p12 PR. The gag gene (MPMVgp2) codes for protein products: Pr78, p14 NC, p10 MA, p24, p12, and p 27. Non-protein coding genes are pro, (MPMVgp3) and pol,(MPMVgp4). http://www.ncbi.nlm.nih.gov/entrez/viewer.fcgi?val=NC_001550.
Virion Structure
MPMV consist of an envelope, a nucleocapsid, and a nucleoid. Virus capsid (core) is enveloped. Proteins constitute about 60% of the particle weight. The viral genome encodes structural proteins and non-structural proteins, in which the non-structural proteins code for an RNA-dependent DNA polymerase. Lipids are present and located in the envelope, and are composed of 35% lipids by weight. The composition of viral lipids and host cell membranes are similar. The lipids are of host origin and are derived from plasma membranes http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/.
MPMV contains unique D-type morphology, similar yet distinguished morphology from type-C and type-B retrovirus. Less dense, knob shaped surface spikes on the envelope, cylindrical capsids (Bohl et.al., 2005), size of intracytoplasmic A-type particles, and eccentric nucleoid region (Fine and Schochetman, 1978) distinguishes MPMV as a Betaretrovirus.
Two types of particles classify MPMV. A-type particles are intracytoplasmic,electron-dense, ring-shaped particles measuring about 70 m/u in diameter. These immature particles pre-assemble in the cytoplasm and may occur singly or in cluster (Mason, 1970). Fully formed immature particles subsequently migrate to the plasma membrane where envelopment and budding occur at the cell surface (Sakalian et al., 2002). Upon release, nascent immature particles undergo a maturation process to acquire infectivity (Bohl et al., 2005). These mature extracellular particles are composed of a well defined spherical oval membrane and a central dense nucleoid measuring about 110 m/n in diameter. The mature particles are connected to or very close the plasma membrane (Mason, 1970).
Ecology
Mason Pfizer monkey virus was first isolated from mammary breast adenocarcinoma in rhesus monkey, an Old World monkey, an infects
Exogenous and endogenous D-type viruses infect a variety of mammalian hosts including New World monkeys, (squirrel monkey retrovirus [SMRV], sheep (Jaagsiekte sheep retroviruss), goat (enzootic nasal tumor virus), as well as D-type virus sequences in humans (Bohl et al., 2005).
With direct hybridization of radioactive MPMV 70S RNA to DNA of various animal species, it has been shown that a portion(approximately 20%) of the MPMV genome was present in the cellular DNA of several Old World monkeys of the subfamily Cercopithecinae. No sequence homology was observed between MPMV and the cellular DNA's of New World monkeys, apes (including man), and several nonprimates (Fine and Schochetman, 1978).
Pathology
By itself, genomic nucleic acid of MPMV is not infectious. Viral protease activity is strictly limited to the completion of the viral budding process (Parker and Hunter, 2001).
Reverse transcriptases (RTs) catalyze the conversion of single-stranded RNA into double-stranded viral DNA for integration into host chromosomes. Proteins in this subfamily contain long terminal repeats (LTRs) and are multifunctional enzymes with RNA-directed DNA polymerase, DNA directed DNA polymerase, and ribonuclease hybrid (RNase H) activities. The viral RNA genome enters the cytoplasm as part of a nucleoprotein complex, and the process of reverse transcription generates in the cytoplasm forming a linear DNA duplex via an intricate series of steps. This duplex DNA is colinear with its RNA template, but contains terminal duplications known as LTRs that are not present in viral RNA. It has been proposed that two specialized template switches, known as strand-transfer reactions or "jumps", are required to generate the LTRs PMID 9831551.
MPMV induces a fatal immunodeficiency syndrome in rhesus macaques (Conte et al., 1997).
Current Research
Enter summarries of the most rescent research here--at least three required
1) MPMV as a vector
2) Ancestral relations, origins
3)
References
Edited by student of Emily Lilly at University of Massachusetts Dartmouth.
