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What is the structure of picornaviruses?
What is the structure of picornaviruses?
What is the primary mode of transmission for viruses in the Flavivirus genus?
What is the primary mode of transmission for viruses in the Flavivirus genus?
Which protein remains buried within the capsid of picornaviruses?
Which protein remains buried within the capsid of picornaviruses?
What type of genetic material do picornaviruses have?
What type of genetic material do picornaviruses have?
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Which of the following statements about the Pestivirus genus is accurate?
Which of the following statements about the Pestivirus genus is accurate?
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Which virus is contained within the Hepacivirus genus?
Which virus is contained within the Hepacivirus genus?
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Which of the following diseases is NOT caused by picornaviruses?
Which of the following diseases is NOT caused by picornaviruses?
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How many copies of M and E proteins are found in a flavivirus virion?
How many copies of M and E proteins are found in a flavivirus virion?
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What is unique about the 5’ and 3’ ends of the picornavirus RNA genome?
What is unique about the 5’ and 3’ ends of the picornavirus RNA genome?
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What structural feature do mature flavivirus particles possess?
What structural feature do mature flavivirus particles possess?
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What is the primary role of eIF-4F complex in the translation process of cellular RNAs?
What is the primary role of eIF-4F complex in the translation process of cellular RNAs?
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What impact does proteolytic cleavage of eIF-4G have on the host cell during picornavirus infection?
What impact does proteolytic cleavage of eIF-4G have on the host cell during picornavirus infection?
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How does the 40S ribosomal subunit initiate translation after scanning the mRNA?
How does the 40S ribosomal subunit initiate translation after scanning the mRNA?
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What is a consequence of failing to properly recruit eIF-4E during picornavirus infection?
What is a consequence of failing to properly recruit eIF-4E during picornavirus infection?
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Which of the following best describes how picornavirus proteins are produced?
Which of the following best describes how picornavirus proteins are produced?
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What characterizes the genome of flaviviruses?
What characterizes the genome of flaviviruses?
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How are the proteins of flaviviruses generated from their genome?
How are the proteins of flaviviruses generated from their genome?
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Which of the following structural proteins is found in the mature virion of flaviviruses?
Which of the following structural proteins is found in the mature virion of flaviviruses?
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What is unique about the E protein in flaviviruses?
What is unique about the E protein in flaviviruses?
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What role do viral and cellular proteases play in flavivirus replication?
What role do viral and cellular proteases play in flavivirus replication?
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What mechanism assists in the entry of flaviviruses into host cells?
What mechanism assists in the entry of flaviviruses into host cells?
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What is the consequence of antibody-dependent enhancement (ADE) in flavivirus infections?
What is the consequence of antibody-dependent enhancement (ADE) in flavivirus infections?
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Which characteristic distinguishes flaviviruses from togaviruses?
Which characteristic distinguishes flaviviruses from togaviruses?
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What is the primary role of proteinases in the Picornavirus life cycle?
What is the primary role of proteinases in the Picornavirus life cycle?
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What is the function of the internal ribosome entry site (IRES) in Picornaviruses?
What is the function of the internal ribosome entry site (IRES) in Picornaviruses?
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Which proteins are primarily encoded by the P1 region of the Picornavirus genome?
Which proteins are primarily encoded by the P1 region of the Picornavirus genome?
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What characterizes the structure of the IRES elements in Picornaviruses?
What characterizes the structure of the IRES elements in Picornaviruses?
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How do virions of Picornaviruses typically enter host cells?
How do virions of Picornaviruses typically enter host cells?
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What structural feature allows Picornavirus virions to bind to cellular receptors?
What structural feature allows Picornavirus virions to bind to cellular receptors?
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What is the composition of the VP1-4 proteins in Picornaviruses?
What is the composition of the VP1-4 proteins in Picornaviruses?
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What is the likely function of the pyrimidine-rich tract found in IRES elements?
What is the likely function of the pyrimidine-rich tract found in IRES elements?
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What mechanism facilitates the entry of Flaviviruses into host cells?
What mechanism facilitates the entry of Flaviviruses into host cells?
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Which protein is cleaved to release the mature C protein after its synthesis?
Which protein is cleaved to release the mature C protein after its synthesis?
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What role does the prM protein play in the Flavivirus lifecycle?
What role does the prM protein play in the Flavivirus lifecycle?
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During Flavivirus replication, what is produced in significantly larger amounts?
During Flavivirus replication, what is produced in significantly larger amounts?
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What is the function of the furin protease in the Togavirus lifecycle?
What is the function of the furin protease in the Togavirus lifecycle?
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What type of RNA genome do Togaviruses possess?
What type of RNA genome do Togaviruses possess?
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How many structural proteins are translated from Togavirus subgenomic mRNA?
How many structural proteins are translated from Togavirus subgenomic mRNA?
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What component is crucial for the assembly of the Flavivirus at intracellular membranes?
What component is crucial for the assembly of the Flavivirus at intracellular membranes?
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What initiates the translation of the Flavivirus genome in the host cell?
What initiates the translation of the Flavivirus genome in the host cell?
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What term describes the viral RNA replication process that results in new plus-strand RNA for various purposes?
What term describes the viral RNA replication process that results in new plus-strand RNA for various purposes?
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What is the primary consequence of receptor-mediated endocytosis for Togaviruses?
What is the primary consequence of receptor-mediated endocytosis for Togaviruses?
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What characteristic feature do Togavirus particles exhibit?
What characteristic feature do Togavirus particles exhibit?
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What type of signal sequence is involved in the synthesis of the capsid protein precursor in Flaviviruses?
What type of signal sequence is involved in the synthesis of the capsid protein precursor in Flaviviruses?
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What is a major public health concern related to Togaviruses?
What is a major public health concern related to Togaviruses?
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Study Notes
Positive Strand RNA Viruses
- Picornaviruses, Flaviviruses, Togaviruses are positive strand RNA viruses.
Picornaviruses - Structure
- Picornaviruses are small RNA genome viruses.
- They have a naked icosahedral capsid (non-enveloped).
- The diameter is approximately 30 nm.
- Hundreds of viral species infect humans, mammals, birds, fish, and other organisms.
- They cause diseases like hepatitis, myocarditis, the common cold, and polio.
Picornaviruses - Genome and Proteins
- Picornaviruses bind to cellular receptors.
- Mature virions have 60 copies of each of the following three to four proteins: VP1, VP2, VP3, and VP4.
- Viral protein VPg is covalently bound to the 5' end of the RNA, instead of a 5' cap.
- P1 encodes structural proteins.
- P2 and P3 encode non-structural proteins.
- The 5' non-coding region contains an internal ribosome entry site (IRES) that allows translation initiation.
- This IRES has extensive secondary and tertiary structures that interact with other cell proteins.
- The polyprotein is processed into individual proteins by viral proteinases.
Picornaviruses - Entry
- Poliovirus RNA enters the cytoplasm after major rearrangement of VP4 and hydrophobic N-terminal VP1, creating a channel in the membrane.
Flaviviruses - Structure
- Flaviviruses are spherical, enveloped particles about 50nm in diameter.
- They have a spherical nucleocapsid with icosahedral symmetry.
- They lack projections, having a "golf ball" appearance.
- Surface glycoproteins are arranged with icosahedral symmetry.
Flaviviruses - Genome and Proteins
- Flaviviruses have a linear, positive sense, single-stranded RNA genome (~10-11 kB).
- It's capped at the 5' end and lacks a poly(A) tail at the 3' end.
- All genes are translated as single polyproteins and cleaved into proteins, including one capsid protein (C), two envelope proteins (M and E), and seven non-structural proteins.
Flaviviruses - Attachment and Entry
- No specific cellular receptor has been identified.
- Entry occurs by endocytosis within clathrin-coated vesicles.
Togaviruses - Structure
- Togaviruses are spherical, enveloped viruses about 70nm in diameter.
- They have envelope projections (spikes) and icosahedral symmetry in both the nucleocapsid and in the envelope glycoproteins.
Togaviruses - Genome and Proteins
- Togaviruses are positive-sense, single-stranded RNA viruses (9.7-11.8 kb).
- They possess a 5' methylated cap and a 3' poly(A) tail (~70 nucleotides).
- They have four non-structural proteins involved in RNA synthesis.
- They have five structural proteins translated from subgenomic mRNAs: one capsid protein, three envelope proteins, and a small hydrophobic protein.
Togaviruses - Genome and Proteins
- The translated genome initially creates a single polyprotein that's later cleaved by host and viral proteases.
- The RNA is initially translated into P123, then further cleaved by proteases into non-structural proteins, then the RNA is further translated into structural proteins from a subgenomic mRNA.
Togaviruses - Assembly and Exit
- Togavirus capsid proteins interact with cytoplasmic tails of envelope proteins.
- Togaviruses exit the cell by budding.
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Description
Explore the world of positive strand RNA viruses with a focus on Picornaviruses. Learn about their structure, genome, and how they interact with host cells. Understand the diseases they can cause and the significance of their proteins in viral life cycles.
