Term
How do Eukaryotic Viruses Replicate? |
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Definition
• adsorption
• penetration and uncoating
• replication of virus nucleic acids
• synthesis of viral proteins
• assembly of virions
• virion release |
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Term
How do non-enveloped vius's enter the cell?
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Definition
Naked viruses such as poliovirus, a picornavirus, may be taken up by endocytosis and then insert their nucleic acid into the cytoplasm through the vesicle membrane. It also is possible that they insert the nucleic acid directly through the plasma membrane within a coated pit. |
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Term
| How do enveloped virus's typically enter cell?(non vesicle way) |
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Definition
Glycoproteins on viral enveope attach to receptors on outside of cell membrane. The viral enveope will fuse with cell and release nucleocapsid into the cell.Some enveloped viruses bind to receptors. Then the membrane of the virus fuses with the host plasma membrane to release the viral capsid into the cytoplasm.
* Other enveloped viruses bind to receptors and trigger endocytosis. The membrane of the endocytosed viruses can fuse with the membrane of the endosome, which is triggered by the acidic environment.
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Term
| How do enveoped virus's enter if fusion is not possible? |
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Definition
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Term
How does the Adenovirus infect the cell?(part 1)
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Definition
| The virus internalizes in clathrin-coated vesicles, then is transported to endosome. When the pH drops below 6, the virus lyses the endosome and escapes into the cytoplasm. The virus particles are transported along microtubules to the nuclear pore, where the capsids disassemble to allow the viral DNA to slip through the nuclear pore into the nucleus. In the nucleus, the dsDNA serves as a template for the production of viral mRNA, and this transcription is done by the host RNA polymerase. |
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Term
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Definition
Adenoviruses are medium-sized (90–100 nm), (naked) viruses composed of a and a double-stranded linear genome. They represent the largest nonenveloped viruses.due to their large size, they are able to be transported through the endosome The virion also has a unique "spike" or associated with each penton base of the that aids in attachment to the host cell via the coxsackie-adenovirus receptor on the surface of the host cell.
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Term
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Definition
| Adenoviruses cause respiratory infections and enteritis. Adenoviruses are non-enveloped viruses with a linear dsDNA genome. They have an icosahedral capsid with long fibers sticking out of each vertex of the icosahedron. The fibers are used by the virus to adsorb to the host cell receptor called coxsackie-adenovirus receptor. The virus internalizes in clathrin-coated vesicles, then is transported to endosome. When the pH drops below 6, the virus lyses the endosome and escapes into the cytoplasm. The virus particles are transported along microtubules to the nuclear pore, where the capsids disassemble to allow the viral DNA to slip through the nuclear pore into the nucleus. In the nucleus, the dsDNA serves as a template for the production of viral mRNA, and this transcription is done by the host RNA polymerase. Viral mRNA then leaks out of the nucleus through the nuclear pore, and is translated in cytoplasm to make viral proteins. One of these viral proteins, the DNA polymerase, travel BACK into the nucleus and make new copies of the adenovirus genome. The capsid proteins also migrate BACK into the nucleus, and form capsids there. Many new adenovirus particles accumulate in the nucleus, Adenoviruses cause the nucleus and cell to lyse, releasing the progeny viruses to infect other cells. |
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Term
What is the
Herpesviridae ? |
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Definition
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Herpesviridae is the largest family of human and animal viruses. Herpesviruses contain a linear dsDNA genome that encodes 70-200 genes.
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These viruses are enveloped viruses. They have an icosahedral capsid, surrounded by a proteinaceous tegument, and then enclosed by a membrane.
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Term
| What is the Herpesvirus replication cycle? |
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Definition
a ) Attachment and entry. b ) Transcription. Three classes of viral genes are transcribed and translated into proteins. Immediate-early proteins (yellow) participate in further transcription.c ) Replication. Early proteins synthesize new viral DNA molecules using circularized input DNA as a template. d ) Assembly, encapsidation and nuclear egress. Late proteins (blue) are made for capsid assembly, DNA packaging and virion release.e) Attachment and entry. Viral membrane proteins on virus particles bind to cellular receptors on the plasma membrane of the cell, which initiates fusion of the two membranes. Nucleocapsids containing the viral genome (red hexagons) are liberated into the cytoplasm and transported to nuclear pores. Viral DNA is released into the nucleus and circularizes. F) Transcription. Three classes of viral genes are transcribed and translated into proteins. Immediate-early proteins participate in further transcription.g) Replication. Early proteins (green) synthesize new viral DNA molecules using circularized input DNA as a template. |
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Term
| What is the Herpesvirus replication cycle(more info) |
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Definition
Assembly, encapsidation and nuclear egress. Late proteins (blue) assemble into capsids, which incorporate newly replicated viral DNA. Nucleocapsids leave the nucleus by budding through the inner nuclear membrane (a process termed ‘envelopment’) into the perinuclear space. Through a complex process of de- and re-envelopment, mature virus particles reach exocytic vesicles, which fuse with the plasma membrane and release new virus particles into the extracellular space. |
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Term
What are the 8 types of human herpesviruses? |
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Definition
HSV-1: oral herpes, cold sores.
HSV-2: genital herpes
Varicella-zoster virus: chickenpox, shingles
Epstein-Barr virus: infectious mononucleosis, Burkitt’s lymphoma, nasopharyngeal carcinoma.
Human cytomegalovirus: birth defects, blindness.
Kaposi’s sarcoma-associated herpesvirus
HHV6 and HHV7 |
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Term
What are the Herpesviruses that cause cancer? |
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Definition
a) Kaposi’s sarcoma-associated herpesvirus
b)Epstein-Barr virus: Burkitt’s lymphoma, nasopharyngeal carcinoma.
c)Other viruses that are linked to cancer: Human papillomaviruses(Papovaviridae): cervical cancer. |
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Term
Structure of Vaccina Virus?
"also it was the virus used to develop vaccination against smallpox" |
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Definition
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Term
| What is latency and what virus is capable of it? |
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Definition
| Herpesviruses are capable of replicating rapidly in some tissue types, and also can "hide out" in other cell types such as neurons where they don’t reproduce. This latter feature of herpesviruses is called latency, and shows similarities to lysogeny in bacteriophages. For example, HSV-1 and Varicella-zoster virus can stay latent in nerve cells, and can be activated years/decades later. In a latent cycle, a herpesvirus-encoded protein called LANA (Latency-Associated Nuclear Antigen) attaches the virus DNA to host cell chromosome. The herpesvirus DNA in this latent form is called episome. |
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Term
| Why do virus's have more hurdles to go through in Eukaryotic cells? |
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Definition
| Eukaryotic cells are more compartmentalized than are bacterial cells. In particular, replication and transcription normally occur in the nucleus, while translation normally takes place in the cytoplasm. These features of eukaryotic cells present hurdles for virus reproduction. |
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Term
How do non-enveloped vius's enter the cell?
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Definition
Many non-enveloped viruses bind to receptors, and are endocytosed. Then the viral nucleic acids can be released from the endosome.
Other non-enveloped viruses bind to receptors on plasma membrane, and create a hole in the membrane. Then the viral nucleic acids can be directly released into host cytoplasm. |
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Term
| What happens usually when eukaryotic virus enters cell?(general)(what is used by host) |
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Definition
Once entering the cell, many (but not all) eukaryotic viruses must navigate between the nucleus and cytoplasm if they use the host enzymes for replication and transcription (both in nucleus) and translation (in cytoplasm). Movement through the nuclear membrane is not too difficult, since there are nuclear pores that normally allow exit of mRNA from the nucleus to the cytoplasm, and transport of some proteins from cytoplasm into nucleus. |
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Term
| How do Eukaryotic Viruses release their progeny virions? |
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Definition
We continued to look at general features of eukaryotic virus lifecycles. Eukaryotic viruses release their progeny virions by two general mechanisms: (i) they lyse the host cells and release virus particles, such as in the case of adenovirus; (ii) enveloped viruses can get out of host cells through budding from plasma membrane, and this way they don’t break the host cells. |
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Term
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Definition
| We briefly looked at a third example of DNA viruses: poxviruses, the largest known animal viruses. Poxviruses contain a linear dsDNA genome and a pretty complex virion structure. The members of this group of viruses cause smallpox (caused by variola virus) and cowpox (by vaccinia virus). |
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Term
| How do Pox Viruses infect a cell? What does it make? |
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Definition
| The virus enters the host cell cytoplasm through membrane fusion. The virus packs a virally encoded RNA polymerase in its core, and this enzyme transcribes viral genes directly from the viral genome. The virus also makes its own DNA polymerase to replicate viral DNA in the cytoplasm. So poxviruses never need to enter the cell nucleus, which is different from the cases of adenoviruses and herpesviruses. |
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Term
| What type of nucleic acid does Eukaryotic RNA viruses have? |
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Definition
Eukaryotic RNA viruses
single-stranded (positive- or negative-stranded)
double-stranded
one RNA molecule
multiple RNA molecules (segmented genome) |
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Term
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Definition
| Polymerases are named by what they make (DNA Polymerase or RNA Polymerase), and by what they read (DNA-dependent or RNA-dependent): |
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Term
What type of polymerase do
-normal celluar DNA replication use?
-noraml cellular transcriptions use?
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Definition
Normal cellular DNA replication uses a DNA-dependent DNA Polymerase.
Normal cellular transcription uses a DNA-dependent RNA Polymerase.
Some viruses (such as poxviruses) have their own DNA-dependent RNA Polymerase.
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Term
| What do most RNA viruses encode for(polymerase wise)? |
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Definition
| Most RNA viruses encode an RNA-dependent RNA Polymerase. Normally cells don’t have RNA-dependent DNA Polymerase. (there are exceptions) |
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Term
| What is the picornavirus? What virus types does it include? |
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Definition
| The picornaviruses ("pico-RNA-viruses") include the rhinovirus and poliovirus. These viruses have no envelope, and have an icosahedral capsid enclosing a positive-stranded RNA genome. |
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Term
| How do Polio Viruses infect cell? |
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Definition
Poliovirus binds to its receptor CD155 and release RNA at the plasma membrane into cytoplasm. Rhinoviruses bind to intercellular adhesion molecule I (ICAM-I), are endocytosed, and are activated inside the endosome/lysosome to release RNA into the cytoplasm. This viral RNA serves as a large mRNA that is translated to make a single polyprotein that cuts itself up into several smaller proteins. One of these smaller proteins is an RNA-dependent RNA Polymerase, that makes - strand RNA from the original genome, and then uses that - strand RNA as a template to make many copies of + strand RNA to be assembled into mature viruses. Progeny viruses are released by cell lysis |
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Term
| How does the Adenovirus infect the cell?(part 2) |
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Definition
| Viral mRNA then leaks out of the nucleus through the nuclear pore, and is translated in cytoplasm to make viral proteins. One of these viral proteins, the DNA polymerase, travel BACK into the nucleus and make new copies of the adenovirus genome. The capsid proteins also migrate BACK into the nucleus, and form capsids there. Many new adenovirus particles accumulate in the nucleus, and you can see a crystalline array of the virus particles. Adenoviruses cause the nucleus and cell to lyse, releasing the progeny viruses to infect other cells. |
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Term
| What do Rhinoviruses cause? |
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Definition
| Rhinoviruses cause most cases of common cold. |
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Term
| How are Polio viruses absorbed? Where can they go and what can happen? |
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Definition
| Poliovirus is adsorbed through the throat or intestine, and grows there. They can move to the spinal cord or even brain, which can lead to damage to the nervous system. |
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Term
| How are vaccines prepared? |
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Definition
We mentioned preparation of vaccines using inactivated virus and attenuated live-virus. We also briefly talked about other types of vaccines: DNA vaccine and recombinant vector.
A vector is a vehicle used for injecting DNA into a cell.
-A recumbent vector is a vector in which foreign DNA has been injected into it. |
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Term
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Definition
It belongs to the reoviridae family, and causes severe diarrhea.
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