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54 Cards in this Set

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List six plus stranded RNA virus families.
Coronaviridae
Flaviviridae

Picornoviridae
Astroviridae
Togaviridae
Caliciviridae

(hepeviridae)
Where do ALL PLUS stranded RNA viruses replicate?
In the cytoplasm
For plus-stranded RNA, the genomic RNA serves as a?

What process is first utilized by genomic PLUS RNA?
- what provides this?
- what is the product of this process
- what is that product subjected to?
message

translation
- cellular translation factors
- Polyprotein
- Virally-encoded proteases cleave the polyprotein.
T/F - For plus-stranded RNA, the genomic RNA is infectious.
True
T/F - For plus-stranded RNA, the virions contain enzymes.
False.

Plus-stranded RNA do not contain enzymes
Since PLUS RNA VIRUS has no enzymes associated, how does it get viral proteins?
Genomic viral RNA translated into polyproteins by cellular factors.

Polyprotein is then cleaved by inherent virally-encoded proteases
PLUS RNA VIRUS REPLICATION
GENERAL STEPS

- What first happens with the incoming virion?
- Uncoated

then

-RNA genome released in to cytoplasm
PLUS RNA VIRUS REPLICATION
GENERAL STEPS

- Once viral PLUS RNA is dumped into cytoplasm, what happens?

- what is produced as a result?
- what significant molecule is produced here also?
- Translation

- Nonstructural viral proteins
(enzymatic)

- Viral RNA PY
PLUS RNA VIRUS REPLICATION
GENERAL STEPS

- the RNA genome replicated by generating what?
- a NEGATIVE-stranded INTERMEDIATE
PLUS RNA VIRUS REPLICATION
GENERAL STEPS

T/F : Structural proteins are translated in all virus families.
FALSE:

in SOME, but not all
PLUS RNA VIRUS REPLICATION
GENERAL STEPS

Once the viral RNA PY makes the MINUS intermediate, what makes from it, additional copies of the PLUS Strands?
- same ol' RNA PY
PLUS RNA VIRUS REPLICATION
GENERAL STEPS

Once progeny is made, what happens to them?

Then what?
They are packaged

Virions leave the cell
(thru various types of mechanisms)
PLUS RNA VIRUS REPLICATION
GENERAL STEPS

Briefly go over all the 6 steps.
1. Virions are UNcoated & Genome is released into cytoplasm

2. Translation to produce NON-structural (enzygmatic) viral proteins
(including RNA Pol Y

3. MINUS stranded INTERMEDIATE made to replicate genome

4. Structural proteins made in some families

5. Progeny virions are packaged

6. Virions exit the cell
Which families of plus-stranded RNA viruses translate only one polypeptide?
Picornoviridae

Flaviviridae
Which families of plus-stranded RNA viruses translates one polypeptide early and one polypeptide late.
Caliciviridae

Togaviridae
Picornoviridae family:

- capsid
- diameter
- envelope?

- unique aspect?
ICOSAHEDRAL

30nm

NOT enveloped

Shuts down cellular translation
(cleaves 4G & IRES recrutis)
(so no need 4E (CBP))
List 6 members of Picornoviridae family affecting humans as natural hosts.
PiCoRnA - HA
1. Poliovirus (Entero genus)
2. Coxsackievirus (ENTERO genus)
3. Rhinovirus (RHINIO genus)
4. Hepatitis A (HEPATO genus)

5. Human Parechovirus (PARECHO genus)
6. Aichi virus (KOBO genus)
How many regional divisions does the picornovirus polyprotein have?

List them & their functions.
Three


P1 - Viral capsid proteins

NON-STRUCTURAL:
P2 - Protein processing & Genome replication
P3 - Protein processing & Genome replication
In plus stranded RNA viruses, why must translation occur first? x2
1. No cellular RNA PY can copy viral genome.

2. No viral enzymes are packaged in particle
VIRAL TRANSLATION

Picornoviridae lacks a 5' cap. What occurs as a result?
VPg exists,
AND
it is cleaved as soon as the as the viral RNA enters cytosol.
VIRAL TRANSLATION

During picornoviridae translation, ribosomes will bind to what?
IRES
(extensive regions of secondary structure)
VIRAL TRANSLATION

Host translational factors can be recruited and associate with what 2 things.
5' caps (cellular)

&

IRES elements (picornovirus)
VIRAL TRANSLATION

T/F - Viral mRNA can NOT be translated when cellular translation is inhibited.
False.

Viral mRNA is still translated even though cellular translation is inhibited.
How do you expand the number of functions encoded by limited sequence information?
Multiple processing events.
T/F - Picornovirus RNA replication is symmetric.
False

It is Asymmetric
(25 to 65x more +sense than -sense)
How conservative is picornovirus RNA replication?
Error-prone

misincorporating 1-2 nucleotides per replication event.
Picornovirus capsid:

- composition
- Shel formed how?
VP1, VP2, VP3, VP4

with
VP1, VP2, VP3 interaction,
with VP4 internal
Discuss the rate of replication for a picornovirus.
Very rapid (5-10 hrs)
PICORNAVIRIDAE
PARTICLES ASSEMBLY

- Describe the steps
1.) P1 encodes (V0, V1, & V3) a PROTOMER (5S)

2.) Five protomers combine to make a PENTAMER (14S)

TWO PATH OPTIONS

3a.) Pentamers can merge to form a EMPTY CAPSID, later addition makes iit a provirion

3b.) pentamers merge to form a PROVIRUS

4.) VO is cleaved to V2 & V4

5.) After cleavage we get a VIRION (160S)
Flaviviridae family:

- capsid
- size
- envelope

- 3 important genera
- ICOSAHEDRAL
- 40-60 nm in diameter
- Enveloped

- Flavivirus
- Hepacivirus (hep C)
- Pestivirus (animal dz)
Flavivirus:

- vectors x2
- thus what kind of virus?
- diseases x3
Mosquitoes & ticks

- Arbovirus

Denque
Yellow Fever
West Nile encephalitis
Flaviviridae Family

- similarities with Picronoviridae?

- differences with Picornoviridae? x2
- only ONE Polyprotein translated

- bigger
- ENVELOPE
Calicivirus family:

- capsid
- size
- envelope?
- 5' cap?
- 3' Poly A?
Icosahedral

35-39 nm in diameter

NOT enveloped

No
(but has VPg covalently)

Yes
List four pathogenic viruses belonging to the Calciviridae genera.

(include associated pathology)
1. Sapovirus
(PEDS gastroenteritis)

2. Norovirus
(NON-bacterial gastroenteritis worldwide)

3. Lagovirus
(Rabbit Hemorrhagic Dz)
(highly contagious & fatal hemorrhagic)

4. Vesivirus
(common cause of resp. dz in cats)
The 5' end of the Calicivirus is uncapped. What is in place to compensate for this?
VPg
(genome-linked protein)
With caliciviruses, production of late polyprotein involves synthesis of what?

- this is found where?
A subgenomic mRNA encoding structural protein.

- in infected cells
List the steps in the Calicivirus replication scheme. x6
1. Virus entry & uncoating

2. Nonstructural protein synthesis

3. Genomic Replication of PLUS sense and MINUS sense

4. Subgenomic RNA replication

5. Structural protein synthesis

6. Particle assembly

7. Particles egress and release from cell
For caliciviruses, what MUST be produced in order for progeny genome production.
Full-length minus strands
What are the two models for production of subgenomic mRNA?
1. Internal initiation

2. Premature termination
For caliciviruses RNA replication, internal initiation must be done on which molecule?
longer-than-subgenomic length minus strands.
For caliciviruses RNA replication, premature termination occurs when?

What occurs?
Minus strand synthesis

Subgenomic sized minus strand serves as template for sgmRNA
Calicivirus uniqueness:

- stability
- capsid x2
- structure

Large hollows at what axes? x2
Extremely stable
(pH 2.7, low [cl-], freezing 60C)

- Single capsid unique to animal viruses.

Contains 90 dimers of capsid protein;
forming shell with
90 archlike
capsomere protrusions

Large hollows at 5- and 3- axes
Togavirus:

- capsid
- size
- envelope
ICOSAHEDRAL

60-80 nm in diamter

Enveloped
List two members of the Togavirus genera.
Alphavirus (arbovirus - mosq. & ticks)

Rubivirus (rubella virus)
List two members that are +stranded RNA that have a 5'cap and a polyA tail.
Coronaviridae

Togaviridae
Coronaviruses:

- capsid
- size
- envelope
Spherical

120 nm

Enveloped
PICORNAVIRIDAE

- List the genera associated with human pathogens. x5

- Which genera has a LEADER protein?
ERK PH

- Enterovirus
- Rhinovirus

- Kobuvirus
- Parechovirus
- Hepatovirus

ONLY Kobuvirus has Leader protein.
PICORNAVIRIDAE

- List the diseases associated with human pathogens (and include their genera)
ENTEROVIRUS
- Polio virus
- Coxsackie

RHINOVIRUS
- Rhino virus

KOBUVIRUS
- Aichi virus

PARECHOVIRUS
- Human Parechovirus

HEPATOVIRUS
- Hepatitis A virus
PICORNAVIRIDAE GENOME @ 5' END

- is there a cap?
- what protein is there?
- fate of this protein?
- NO cap

- VPg

- cleaved upon entering cells cytoplasm
PICORNAVIRIDAE GENOME @ 5' END

- what stretch of genomic region is at the 5' end?

- what does this encode?

- what is its fate?
- UTR (UnTranslated Region)

- encodes NOTHING

- Folds into secondary structure known as IRES
PICORNAVIRIDAE GENOME @ 5' END

- IRES F(x)?

- how can it do so without CBP?

- resultant effect?
- recruits host translation factors

- eIF4G is cleaved, thus eIF4E (CBP) is no longer needed.

- Translation proceeds UNIMPEDED without CBP
PICORNAVIRIDAE GENOME @ 5' END

- what type of proteins are translated from the 5' translation region?

- what about the 3' end?
- Structural proteins
(capsid)

- NON-structural proteins
(enzymatic)
PICORNAVIRIDAE GENOME

Translation for:
- P3B
- P3CD
- P3C
- P3D

Above is an example of?
-VPg

- Protease inhibiting host Transcription
(goes to nucleus)

- Protease

- RNA Polymerase

Multiple processing events expanding the number of Functions encoded by a limited sequence
PICORNAVIRIDAE GENOME

- once a polyprotein is processed, what are the 5 types of resulting proteins?
- Pro-apoptotic
- Anti-apoptotic

- Shuts down host Transcription
(nucleus)
- Shuts down host Translation

- Viral replication complex