Polypurin tract
The polypurine tract (engl. Polypurine tract , PP or PPT) is a region in the genetic material ( genome ) of all retroviruses is common. The PPT is an RNA sequence that consists of at least nine adenosine and guanosine residues (both purine bases ) and is located downstream of the coding genes and in front of the 3 ' LTR . Lentiviruses can also have a second PPT in the middle of the genome ( central PPT, cPPT ). The PPT is in the reverse transcription for the initiation of DNA synthesis required.
Location of the PPT in the genome:
5'-|LTR|--|Gen1|----|Gen2|--........--AAAAGAAAAGGGGGG--|LTR|-3' Ableserichtung---> PPT
The correct sequence of the PPT for the formation and removal of the PPT primer by RNase H important. After the synthesis of the first DNA strand, RNase H breaks down the RNA part of the hybrid strand, down to the bases of the PPT, which are resistant to the RNase. This creates the PPT primer on which the synthesis of the second strand begins.
literature
- Kivie Moldave, Waldo E. Cohn: Progress in nucleic acid research and molecular biology . New York, Academic Press, 1963-, 2005, ISBN 0-12-540080-2 , pp. 238 ff . (English).
- John M. Coffin, Stephen H. Hughes, Harold Varmus: Retroviruses . Cold Spring Harbor Laboratory Press, Plainview, NY 1997, ISBN 0-87969-571-4 , pp. 129 ff .
Individual evidence
- ↑ P. Charneau, M. Alizon, F. Clavel: A second origin of DNA plus-strand synthesis is required for optimal human immunodeficiency virus replication. In: Journal of virology Volume 66, Number 5, May 1992, pp. 2814-2820. PMID 1560526 . PMC 241038 (free full text).