6+7: DNA and RNA multiplication Flashcards
Parts of Eclipse:
- Early transcription, translateion: enzymes
- Replication: nucleid acid multiplication
- Late transcription, translation: structural proteins
Classification of viral families:
- Baltimore system I. dsDNA II. ssDNA III. dsRNa IV. +ssRNA V. -ssRNA VI. viruses using transcriptase
Properties of virus multiplication:
Use of cellular enzymes, ribosomes, nucleotides, amino acids and energy
Properties of virus multiplication of DNA virus:
the NA is similar to the cellular genetic material
Properties of virus multiplication of RNA virus:
RNA does not store information –> needs special enzyme for replication.
- RNA dependent RNA polymerase (RdRp)
- coded by the virus, sometimes carried in the virion
- mutations during replication
Coding system of Cell and Virus:
Cell: monocistronic –> separate mRNAs for the proteins
Virus: lack of space - can be polycistronic
Name some Double stranded DNA viruses:
Papilloma-, Polyoma-, Adeno-, Herpes-, Pox-, Asfarviridae
What happens during Early Transcription in dsDNA viruses?
- the viral DNA enters into the nucleus
- cellular transcriptase: –> mRNA
Except: Pox-, Asfarviridae
- own viral transcriptase
- multiplication in the cytoplasm
What happens during Early Translation in dsDNA viruses?
- on the surface of the ribosomes - cellular translation.
- non-structural protein synthesis
What happens during Replication in dsDNA viruses?
- Viral replicase (better than the cellular, production in abundant amount)
What happens during Late Transcription, Translation in dsDNA viruses?
- The progeny DNAs serve as template
- high amounts of structural protein synthesis
Name som Single stranded DNA viruses:
Parvo-, Circoviridae (circular genome)
What happens during Transcription of ssDNA viruses?
mRNA synthesis fro the coding tread
What happens during Translation of ssDNA viruses?
- cellular translation
- polycistronic mRNA = enzymatic cleavage
What happens during Replication of ssDNA viruses?
- small genome: no own polymerase
- Cellular polymerase copies the dsDNA
- eventually one tread is removed
What is special about Autonomous Parvoviruses, Circoviridae?
- multiplication only in S-phase (dividing) cells
- pathology = enterocyte, embryo, bone marrow cells etc.
What is special about Dependovirus?
use the replicase of adeno- or herpesviruses
Name some dsRNA viruses?
Reo-, Birnaviridae
What is special about Reo- and Birnaviridae?
dsRNA
- segmented genome (Reo-10:12; Birna-2)
- Alien NA for the cell: intensive interferon response, partial decapsidation
What happens during Transcription of dsRNA viruses?
- the dsRNa is not readable for the ribosomes
- viral RdRp - structural: transcription mode = mRNA synthesis
What happens during Translation of dsRNA viruses?
- monocistronic coding: segment - proteins
What happens during Replication of dsRNA viruses?
- the mRNA enters into the inner capsid
- viral RdRp in replicase mode: the mRNA is supplemented with a negative thread
What happens during Late Transcription, Translation of dsRNA viruses?
assembly of progeny virions
Name some +ssRNA viruses?
Picorna-, Calici-, Toga-, Flavi-, Corona-, Arteri-, Astroviridae
What happens during Transcription of +ssRNA?
- genomic RNA - mRNA
- 5´ methyl capped, 3´ polyadenylated
- directly attaches to the ribosomes
What happens during Translation of +ssRNA?
Two different: Plycistronic mRNA and monocistronic mRNA
What happens during Translation of +ssRNA in Polycistronic mRNA?
picornaviruses, flaviviruses
- precursor polypeptide
- protease cleavage
- equimolar protein production
What happens during Translation of +ssRNA in Monocistronic mRNA?
subgenomic mRNA synhtesis
Nidovirales, Calci-, Togaviridae
- for structural protein production
- more accurate synthesis control
What happens during Replication of +ssRNA?
- viral replicase (RdRp, non-structural)
- replicative intermediate forms (RI): dsRNA, -ssRNA
- the -ssRNA is template for the progeny +ssRNA genome
- translation from the progeny RNA
- finally the + threads incorporate into the progeny virions
Name some -ssRNA viruses:
Orthomyxo-, Paramyxo-, Borna-, Filo-, Thabdo-, Arena-, Bunyaviridae
What happens during Transcription of -ssRNA?
- negative sense RNA (3´–>5´)
- not readable for the ribosomes –> viral RdRp- structural
- transcription mode: complementary (+) thread synthesis –> mRNA
- Arenaviridae, vertain Bunyaviruses: Ambisense genome
What happens during Translation of -ssRNA?
monocistronic
- Orthomyxo-, Arena-, Bunyav: segmented
- Mononegavirales: short mRNAs
What happens during Replication of -ssRNA?
the RdRp in replication mode: - dsRNA (RI) in the nucleocapsid - full length +ssRNA synthesis - -ssRNA synthesis finally the negative threads stay in the progeny virions
Name some viruses using reverse transcriptase: RNA/DNA
Retroviridae
What happens during Transcription of Viruses using reverse transcriptase: RNA/DNA?
Genome - mRNA, but:
- reverse transcriptase (structural)
- transcribes to dsDNA
The viral dsDNA integrates into the cellular genome:
- provirus
- cell division - virus genome copying
Transcription:
- cellular transcriptase: mRNA production
- long terminal repeat (LRT) regions: intensive promoter, frequent transcription
What happens during Translation of Viruses using reverse transcriptase: RNA/DNA?
polycistronic mRNA - protease cleavage
What happens during Replication of Viruses using reverse transcriptase: RNA/DNA?
= transcription!
- the mRNA will finally serve as the genome of the progeny viruses
What are Hepadnaviridae?
ss/ds DNA (circular)
What happens during Transcription of Hepadnaviridae?
- repair of the grapped genome: viral polymerase
- cellular transcriptase: mRNA production
- -> short transcripts - proteins
What happens during Translation of Hepadnaviridae?
monocistronic mRNAs
What happens during Replication of Hepadnaviridae?
- full length transcripts of “mRNA” (cellular enzyme)
- maturation: viral reverse transcriptase produces complementary DNA thread
- circularization, partly completed to dsDNA
What are the importance of eclipse strategies?
- consequences on pathogenesis, epidemiology
- detection of replicative intermediate forms - active virus mulitplication
- in vitro protein expression studies
- Anti-viral drug development.: inhibition of virus-specific enzymes ( like HIV!)