Polymerase chain reaction PCR

selective amplification of DNA by repeated cycles of: (1) heat denaturation of the DNA; (2) annealing of two oligonucleotide primers that flank the DNA segment to be amplified; and (3) the extension of the annealed primers with the heat-insensitive Taq DNA poly-merase. The product is termed the 'amplicon'. Can be used to determine the sequence of the amplicon, for virus diagnosis, and in the amplification of low copy number sequences. Amplification of RNA can be achieved by first reverse transcribing the RNA to DNA, followed by PCR. This is referred to as 'RT-PCR'.

Barnes WM (1994) Proc Natl Acad Sci 91, 2216 Saiki RK et al (1988) Science 239, 487

polynucleotide A linear polymer of nucleotide units linked by phosphodi-ester bonds between the 3' and 5' positions on the sugar ring. Long polynu-cleotides are nucleic acids.

polynucleotide kinase An enzyme isolated from bacteriophage T4-infected Escherichia coli, which transfers a phosphate group from ATP and phosphorylates the 5'-OH termini of RNA or DNA chains. Used experimentally to label RNA prior to sequencing.

Lockard RE et al (1978) Nucl Acids Res 5, 37

polynucleotide ligase Generic term for enzymes which catalyze the linking or repair of either DNA or RNA strands. See DNA ligase and RNA ligase.

Polyomaviridae A family of double-stranded DNA viruses with only one genus, Polyomavirus. The family description corresponds to the genus description.

Polyomavirus The only genus in the family Polyomaviridae. The type species is Simian virus 40. Virions are non-enveloped 40nm in diameter with 72 capsomeres arranged in a right-handed skew icosahedral lattice. The genome is a single molecule of circular double-stranded DNA which is 5243bp in length for the type species. Virus-specific proteins are encoded on both DNA strands. Several species hemagglutinate by reacting with neuraminidase-sensitive receptors. Replication occurs in the cell nucleus. During replication, transcription of the genome is divided into early and late stages which are under the control of separate promoters and occur on opposite strands. During replication 2-3 non-structural protein antigens are expressed which include large T, middle T and small t for mouse and hamster poly-omaviruses and large T and small t for other viruses such as SV40, JC and BK viruses. Replication of the viral genome is initiated by binding of the T antigen at a specific site on the DNA and its interaction with host cell DNA polymerases that are used to replicate the DNA. In their natural hosts most species cause silent infections, but on injection into newborn animals (hamsters, mice, etc.) most are oncogenic. Viral DNA is integrated into the cellular DNA of transformed and tumor cells.

polyomavirus bovis (WRSV) A member of the genus Polyomavirus, family Polyoma-viridae. See Bovine polyomavirus.

Schuurman R et al (1990) J Gen Virol 71, 1723

polyomavirus papionis A polyomavirus isolated from the chacma baboon. See Simian virus 12.

polypeptide A chain of amino acids linked together by peptide bonds obtained by synthesis or by partial hydrolysis of a protein. Can also refer to the primary structure of a protein, e.g. polypeptide chain.

polyprotein A large polypeptide that gives rise to two or more proteins by enzymatic cleavage. For example, the human poliovirus genome codes for a large protein which is subsequently cleaved to produce all the virus structural and non-structural proteins.

polyribosomes See polysomes.

polysomes Ribosomes attached to mRNA at intervals of 50-10nm. In the process of protein synthesis the ribosomes pass along the mRNA strand, each forming a polypeptide chain as it goes. Synonym: polyribosomes.

poly U Polyuridylic acid. See poly AU.

Pongine herpesvirus 1 (PoHV-1) A species in the genus Lymphocryptovirus, isolated from lymphoid cell lines of the chimpanzee, Pan troglodytes. A primate B-lymphotropic herpesvirus sharing 40% well-conserved DNA sequence relatedness with Epstein-Barr virus (Human herpesvirus 4) and herpesvirus papio (Cercopithecine herpesvirus 12). All three viruses cross-react antigenically. Cultivation restricted to B cell lymphocytes. No evidence of clinical disease in chimpanzees. Synonyms: chimpanzee agent; chimpanzee herpesvirus 1; pan herpesvirus.

Gerber P et al (1976) J Virol 19, 1090 Heller M et al (1982) J Virol 41, 931

Pongine herpesvirus 2 (PoHV-2) A species in the genus Lymphocryptovirus, isolated from a cell line established from a leukemic orangutan, Pongo pygmaeus. Synonym: orangutan herpesvirus.

Rasheed S et al (1977) Science 198, 407

Pongine herpesvirus 3 (PoHV-3) A species in the genus Lymphocryptovirus. A virus associated with a B lymphoid cell line established from a gorilla, Gorilla gorilla. Cross-reacted in DNA hybridization studies to 30-40% with EBV DNA. Transformed lymphocytes from gibbon apes, Hylobates lar, in vitro. No evidence that the virus causes disease in the host species. Synonyms: gorilla herpesvirus; herpes-virus gorilla.

Neubauer RH et al (1979) J Virol 31, 845

Pongola virus (PGAV) A serotype of Bwamba virus in the genus Bunyavirus. With Bwamba virus forms the Bwamba serogroup. Isolated from mosquitoes in South Africa, Uganda, Ethiopia, Kenya, Mozambique and Central African Republic. On injection kills newborn mice. Natural hosts sheep, cattle and donkeys. Antibodies found in humans but disease not reported.

Ponteves virus (PTVV) A serotype of Uukuniemi virus in the genus Phlebovirus. Isolated from a tick, Argas reflexus, in southern France. Not reported to cause disease in humans.

Poovoot virus (POOV) A serotype of Great Island virus in the genus Orbivirus. Member of the Kemerovo serogroup. Isolated from ticks, Ixodes uriae. Not reported to cause disease in humans.

Yunker CE (1975) Med Biol 53, 302

Porcine adenoviruses A-C (PadV-A to -C)

Three species in the genus Mastadenovirus. There are at least five serological types. Some strains agglutinate erythrocytes of several species. Replicate in a wide range of cell cultures (pig, cattle, dog, hamster and humans). Commonly found in the digestive tract of pigs. On inoculation intranasally into colostrum-deprived newborn pigs, the tonsils and lower intestine become infected but no symptoms or disease are produced.

Derbyshire JB (1989) In Virus Infections of Porcines, edited by MB Pensaert. Amsterdam: Elsevier, p. 73

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