Virus Replication (RNA and DNA) Flashcards
3 Mechanisms for Viral Internalization
Direct penetration (viropexis) Fusion at PM (can cause syncitium formation) Receptor-mediated endocytosis
3 Mechanisms of Uncoating
Initiated by attachment to receptor (like maybe at nuclear membrane)
Promoted by acidic environment or proteases in endosomes
Enveloped viruses uncoat on fusion w/ cell membranes
2 Phases and 2 Periods of Virus Growth Curve
Early Phase - genomic replication going on
Late Phase - after early phase until virus release
Eclipse Period - up until virus assembly
Latent Period - up until virus release
5 Positive Strand RNA Viruses
Picorna, Toga, Flavi, Calici, and Coronaviruses
3 Segmented -Strand RNA Viruses
Orthomyxo, Bunya, and Arenaviruses
3 Nonsegmented -Strand Viruses
Paramyxo, rhabdo, and filoviruses
2 Ambisense -Strand Viruses
Arena and some Bunyaviruses.
Important requirement for - Strand and Double Stranded Viruses
Because must use - strand as template for mRNA, need to carry RNA dep RNA pol
2 Double Stranded RNA Viruses
Reo and rotaviruses
3 Viral Mechs to Enhance Translation of Own Genomes (& Families that do it)
Internal ribosoe entry site (IRES): Picorna and flaviviruses
Cleavage of Cap binding protein: Picornaviruses
Cleavage of cellular mRNA: Orthomyxoviruses
Naked virus assembly and exit
Assembled as capsid and then packaged. Exits via lysis
Enveloped virus assembly and exit
Matrix protein promotes interaction of viral nucleocapsid with the viral glycoprotein modified membranes for assembly, and then release by budding or exocytosis there to get the envelope
Parvovirus Notable Feature
Smallest DNA virus (and thus most dependent)
Parvovirus Notable Genome Feature
Inverted repeats on end serve as primers, can flip to form + and - strands.
Papovirus Notable Genome Feature
Read in one direction it has early T (transformation) genes to encourage cell growth and in the other it has late VP (structural) genes
Adenovirus Early Genes
Transactivator proteins E1A and E1B for cell growth and transformation
Adenovirus 3 Life Cycles
Latent - Viral genome remains in the nucleus
Lytic - full cycle
Oncogenic - changes growth regulation
Immediate Early Genes
In herpes virus, code for DNA binding prots to regulate gene transcription
Herpesvirus Early Genes
DNA Pol and dNTP synth enzymes like viral thymidine kinase, a target for antivirals
4 Herpesviruses with Inverted Repeats (can recomb)
VZV, HSV1&2, CMV
2 Herpesviruses with Direct Repeats
EBV and HHV6
Poxviruses Unique Factor
All replication events take place in cytoplasm. DNA rep occurs in inclusions
Hepadnavirus Notable Genomic Features
Has 3200 bp partial dsDNA circle which completes upon entering the cell to 3500bp. This starts at different points to encode overlapping different 5’ mRNAs that share 3’ end. It encodes RT and makes DNA from the large mRNA.
