CSB351Y1 Lecture Notes - Lecture 12: Rolling Circle Replication, Intergenic Region, Icosahedron
26 May 2018
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Lecture 12: DNA virus replication 2
• ssDNA viruses
- Circular: Geminivirus
- Linear – canine/human Parvovirus (parvus = small)
• Late events in virus life cycle
- Assembly, maturation, exit from cell
Replication Strategy of ssDNA viruses
1. Conversion into dsDNA (replicative form)
2. Early transcription by host enzymes
3. Traslatio of regulator proteis ad rollig irle ssDNA repliatio strad displaeet, ligatio
4. Late transcription
5. Synthesis of late (structural proteins)
6. Sequestering of viral genomic ssDNA
7. Assembly into virions
ssDNA Replication
• Geminiviruses use RNA primer to initiate DNA synthesis and produce dsDNA, replicative form
• Parvoviruses use tandem repeats at the termini of the linear ssDNA genome to form hairpin structures, which
can serve as primers to initiate DNA synthesis and produce a dsDNA replicative form
Geminivirus
• Small ssDNA viruses
• Double capsid morphology
• Circular genome
• Infect a broad spectrum of plants, significant pathogen of crops
Geminivirus Structure
• Non-enveloped, twinned (geminate) incomplete icosahedra (T=1) capsid
• Each geminate particle contains only a single circular ssDNA
Geminivirus genomes can be both monopartite and bipartite
• Constant region (ori), also known as the intergenic region (IR)
• Overlapping open reading frames
• Sense and complementary sense open reading frames
• Transcription is bidirectional, promoters are located in the constant region
- Begomovirus (Bean Golden Mosaic Virus)
- Mastrevirus (Wheat Dwarf Virus)
- Curtovirus (Beet Curly Top Virus)
- Topocuvirus (Tomato Pseudo Curly Top Virus)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Lecture 12: dna virus replication 2 ssdna viruses. Geminivirus: small ssdna viruses, double capsid morphology. Infect a broad spectrum of plants, significant pathogen of crops. Geminivirus structure: non-enveloped, twinned (geminate) incomplete icosahedra (t=1) capsid, each geminate particle contains only a single circular ssdna. Topocuvirus (tomato pseudo curly top virus: rep replication initiator protein, sir & lir short and long intergenic region, taatatt ac rolling circle initiation. Msv maize streak virus: cr constant region similar to ir. Bgm bean golden mosaic virus: mp movement, ren replication enhancer, cp capsid rep, c2, c4 and ren role in symptoms. Intergenic region consists of hairpin structure (required for replication: promotor region (required for initiation of transcription, replication initiated by cleavage of (+) strand by rep and occurs by rolling circle mechanism ssdna genomes. Rep also involved in cell cycle control. Rolling circle replication (rcr) *see video: conversion in dsdna (rf, early transcription by host enzymes, tra(cid:374)slatio(cid:374) of regulator(cid:455) protei(cid:374)s a(cid:374)d (cid:862)rolli(cid:374)g (cid:272)ir(cid:272)le(cid:863) ssdna repli(cid:272)atio(cid:374)
