Lecture 6 Flashcards

Question

Modulation of cap recognition: polio edition

Answer 1

-does viral inhibition by cutting up eLF4E which cleaves the boundaries between the viral proteins. These proteases can also clave eIF4G's link between it an eIF4E(aka cap binding protein). Now no host protein can be made and polio can make viral proteins because in the case of polio its proteins don

Answer 2

they dephosphorylates eIF4E and this sequesters the cap-binding protein

Answer 3

they can regulate protein synthesis and inhibit cellular protein synthesis

Answer 4

-formation of individual structural units of the protein shell from one or several viral proteins -assembly of the protein shell by appropriate and sometimes variable, interactions among structural units -selective packaging of the nucleic acid genome and other essential virion components -some viruses will aquire an envelope -realse from host cell -some viruses will have maturation of virus particles

Answer 5

host cell machinery the viruses might need: -cellular chaperones -transport systems -secretory pathwats -nuclear import and export machinery

Answer 6

factories or inclusions -it concentrate viral proteins to accelerate reactions -in positive start RNA virus these are often sorts of membranous inclusions and these concentrate viral proteins to accelerate reactions. membrane targeting can happen through signal sequences

Answer 7

-membrane targeting: can happen through signal sequences, fatty acid modifications, membrane retention signals -nuclear localization sequences (NLS) -nuclear export signals: to make sure that the virus gets out of the nucleus

Answer 8

-THE NUCLEUS: easier to pack there -the viruses all bring the packing material to the nucleus -for most it happens in the viruses because you don't want it to be found in the cytoplasm by the immune system

Answer 9

Virus particles are complicates -they are not all made at once -sub assemblies ensure ordely formation of viral particles and virion subunits -formation of discrete intermediate structures -aka quality control

Answer 10

-Assembly from individual protein molecules: you produce the individual proteins and they have high affinity with each other and they will automatically find each other and form some kind of assembly in the cell -Assembly from a polyprotein precursor: the proteins could be made as polyproteins and so they associate and then they get cleaved into their mature viral protein -Chaperone assisted assembly: you can make a protein and then it needs to be folded properly by a chaperone from host to take on its mature form

Answer 11

-Sequential ex: polio virus attaches, uncoating, translation, structural unid is made, capsid assembly and then genome is incomporated in the capsid, stuff gets cleaved and then it yeets out of the cell -Concerted ex: influenza it brings in its nucleocaspsid protein and its matrix into the nucleus where it assembles the viral genome segments. Those can zip through the nuclear pore and when they arrive at the surface of the cell they interact with the envelope glycoproteins and that drives budding from the plasma membrane

Answer 12

packaging signals in the viral genome these are discrete sequences that are typically recognized by viral proteins -to know if a particular sequence is a packaging sequence insert it in a cell and see if it is gonna get packaged

Answer 13

herpesvirus replication produces concatemers with head-to-tail copies of viral genome

Answer 14

aka pac 1 and 2 are needed for recognition of viral RNA and cleavage -there are these motor proteins that wind up the DNA into the capsid and when they hit pac 2 then iy cleaves the DNA -this ensures that the right size of DNA is in the capsid

Answer 15

structures RNA which are packaging signals -in the case of retroviruses it is the SL element, it recognizes 2 viral genomes because retrovitruses put 2 genomes in their viral protein -this is because the packaging signal that is recognized is actually the kissing loop interaction between the 2 genomes that gets recognized by the viral protein and then it drags it into the virion particle

Answer 16

-evidence for specific packaging sequence on each RNA segment ex: influenza virus always has 8 rna segments and each has its own packaging signal and that ensures that you get the right number of segments into the viral particle -serial dependance of packaging ex: bacteriophage smth 6: they always put the small segment first, then the medium and then the large in virion, if the small is nit there the medium can't get in

Answer 17

-envelope glycoproteins and capsids drive budding ex: alphaviruses -internal matrix (internal leaflet of viral envelope) or capsid proteins drive budding ex: retroviruses -Envelope proteins drive budding ex: influenza virus -matrix proteins drive budding but additional components needed for efficiency and accuracy ex: ebolavirus Afetr assembly of internal structures (most enveloped viruses) -can occur at many cellular membranes (nuclear membrane, ER, Golgi, plasma membrane, etc)

Answer 18

-Internal structures are assembled in the nucleus and they are transported to the membrane where the matrix proteins drives budding to produce the viral particle -the genome segments are associated with the nucleocapsid and matrix proteins in the zip out the nuclear pore and they are transported on microtubules onto the surface of the cell where the viral glycoproteins are waiting. -internal structure assembly and budding are spatially and temporally separated -matric protein targeted to the membrane (hydrophobic region)

Answer 19

ESCRT pathway -retroviruses undergo a maturation step after they are released from the cell -the retroviral RNA is produced in the nucleus, they get exported and they dimerize and bind to the structural proteins that target it to the cell membrane=budding -maturation happens after the viral particle has left the cell by a protease cleavage event within the virion aka they mature once they leave the cell Late (L) domains bind cellular proteins involved in vesicle trafficking, needed for virus release (found in + and - enveloped RNA viruses)

Answer 20

DNA virus: they replicate in the nucleus, they bud out of the nucleus into the ER, then bud out into the golgi where they are decorated with their envelope glycoprotens. they bud out of the golgi into a secretory vesicle and they undergo exocytosis they are only infectious when they have their envelope from golgi

Answer 21

Dengue created its virion in the ER and passes through the trans golgi network and the change in pH and the exposure to the furin molecule causes a cleavage event that cleaves the PR protein and then the viral proteins are released and the PR proteins are also release and then the viral proteins are mature

Answer 22

-a lot of proteins sometimes they don't wanna infect the cell that they just came from -they'll down-regulate the receptor for the virus so that no other virus can reinfect - vaccinia builds these actin tails and propels the virion away from the cell to prevent it from coming back and reinfecting it

Answer 23

Cell lysis: -apoptosis, necroptosis -viral protein can induce rupture of cell membranes (ex: viroporins) -loss of membrane integrity with inhibition of protein synthesis Non-lytic release -vesicular release ex: polio -exocytosis/exosomes (some virus can gain transient envelopes)