MICI 2100 Lecture Notes - Lecture 14: Rna-Dependent Rna Polymerase, Enterobacteria Phage P22, Restriction Enzyme
1 Oct 2016
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Document Summary
Many viruses can establish a dormant state in the host cell. In temperate phage this is called lysogeny (p22 phage in salmonella). In animal viruses this is called latency (e. g. hiv in memory cd4 t-cells, hsv-i in neurons, Latent infections do not cause cell stress or make products that attract the immune system"s attention and so maintains long-term persistence in their hosts. Latency can be achieved by: integration into the host genome (retroviruses), or, long term retention of viral episome (herpes virus). After penetration, viral dna is delivered into host. Host gene expression is arrested immediately: host dna/rna degradation, inhibition of protein synthesis. Formation of new viral particles starts at 12 minutes. Lysis of host and release of viral particles at 30 minutes. Restriction endonucleases are enzymes that cut dsdna at specific nucleotide sequences known as restriction sites. Host dna is methylated by a host enzyme (methylase) to protect it from the restriction enzyme"s activity.
