Intracellular Trafficking Flashcards
Virion components are produced in multiple cellular “compartments” T/F
T
Animal cell diameters range between
10-30 micrometers
_____ is not sufficient for intracellular trafficking
diffusion
Viral components are most commonly moved on
microtubules
Assembly of most ___ virus takes place in the nucleus
DNA ex. adenovirus, papillomavirus
Structural proteins are ____ into the nucleus after syn.
imported
Assembly of herpesvirus is within the ____; however it is finished at _______ sites.
nucleus; extra-nuclear
All viral structural proteins enter the nucleus via the ___________
normal cellular pathway of nuclear protein import
Proteins destined for the nucleus encode ______
nuclear localization signals
The nuclear localization signals are recognized by the
nuclear import machinery
Entry into the nucleus can be done when the protein is ____; such as polyomavirus, or via a ____ _____, such as an adenoviral protein
preassembled; viral chaperone
The nucleus has 3k to 4k ____ _____ _____, each with a very high translocation capacity
nuclear pore complex
_____ ______ depends on the limited supply of soluble transport proteins.
Nuclear import
viral and cellular proteins ____ for entry into the nucleus
compete
large DNA viruses produce so many structural proteins that cellular protein synthesis is _____
inhibited
Many viral structural proteins enter infected nuclei as _____ structural components
multimeric
viral membrane proteins reach their destination via the cellular ____ ______
secretory pathway
Viral envelope glycoproteins are translated into the ___ _____ and folded and assembled there
ER lumen
They travel via ______ _______ to and through the golgi apparatus and from golgi to plasma membrane
transport vesicles
The _____ ______ of the virus and the viral genome are also directed to plasma membrane sites of assembly
internal proteins
Transmembrane segments of glycoproteins usually separate _____ extracellular from _____cytoplasmic domains
large; smaller
________ domains are crucial for viral entry, whereas the ______ are important in virus assembly
extracellular; intracellular
Ribosomes synthesizing proteins for the secretory pathway are generally found on the ____ face of the ___
Cytoplasmic; ER
The association of ribosomes with the ER membrane is directed by a short sequence in the ____ protein called the ____ _____>
nascent; signal peptide
Signal peptides are found at the __-termini of proteins destined for the secretory pathway
N
Signal peptides are approximately ____ amino acids in length
20
The signal peptide is recognized by the ____ _____ _____
signal recognition particle
What are the steps of influenza virus HA0 protein maturation?
- Translocation 2. disulfide bond formation/glycosylation 3. protein folding
Translocation continues until what enters the ER lumen?
The entire polypeptide chain
The folding and initial _______ ______ of proteins that enter the secretory pathway take place in the ER
postranslational modification
The lumen contains many ____; which help to catalyze chemical modifications such as disulfide bond formation, glycosylation, folding promotion, oligomerization
enzymes
Viral envelope glycoproteins are modified by the addition of oligosaccharides to _____, ______, or _____
asparagine, serine, or threonine
each glycoprotein population comprises a heterogenous mix of _____
glycoforms
The hydrophilic oligosaccharides are present on the surface of a virus, creating a ____ ____, which in effect masks the protein’s surfaces and epitopes which can be recognized by _____ antibodies
sugar shell; antiviral
Intramolecular disulfide bonds occur between pairs of ____ residues
cysteine
disulfide bonds would rarely form in the ____ environment of the cytoplasm; but the ____ environment of the ER lumen is a good location for this
reducing; oxidizing
most viral membrane proteins are _____ that assemble as their constituent protein chains are folded and covalently modified.
oligomers
This assembly begins in the ____ as the surfaces that mediate interactions among protein subunits adopt the correct conformation.
ER
HA0 _____are constricted to the ER lumen, whereas _____ are found in this and subsequent compartments of the secretory pathway.
monomers, trimers
Herpes simplex type 1 proteins gH and gL must ____ with each other in order to leave the ER
interact
The first step of the secretory pathway is transport of the folded protein from the ____ to the ____
ER; Golgi
Proteins enter the Golgi Apparatus from the ER via the ___-_____ network.
cis-golgi
The ___-____ network forms the exit face of the Golgi.
trans-golgi
Some viral envelope glycoproteins are also processed by cellular enzymes in late Golgi compartments. T/F
T
Retroviral envelope proteins are cleaved in the trans-golgi to form the TM (transmembrane) and SU (surface unit) subunits from the precursor t/f. What is also cleaved here? What is this essential for?
T; HA0 into HA1 and HA2; formation of an infectious particle. not necessary for assembly
in Neurons, transport to (anterograde) synaptic vesicles is controlled by ____ motors. transport to the nucleus (retrograde) is controlled by ____ motors. This is performed along what cellular structure?
kinesin; dynein; microtubules
Several virus encode proteins that _____ transport of MHC I molecules to the plasma membrane
interfere with
Adenovirus ___ protein binds to MHC in the ___ and prevents exit
E3; ER
Human cytomegalovirus US11 and US2 gene products induce transport of MHC from the ER to the ____ for rapid degradation by what cellular enzyme? HIV1 ___ protein induces selective degradation of new MHCI by a similar mechanism
cytosol; proteasome; Vpu
Viral envelopes can be acquired from a variety of ____ membranes, not just the plasma membrane. Most assemble at the ____ face of compartments of the _____ pathway
internal membranes; cytoplasmic; secretory
Complex virus such as herpesvirus and poxvirus interact with ___ ____ ____ during assembly and exocytosis
multiple internal membranes
Viral assembly site is determined by the ____ location of _____ _____ ____
intracellular; viral envelope proteins
The synthesis and packing of most ___ genomes takes place in the infected ____ ____
DNA; cell nucleus
For most RNA virus, packing and assembly takes place in the _____. These genomes must be relocated to the appropriate ______
cytoplasm; cytoplasmic membrane
Retroviral RNA genomes are -___ RNA transcripts synthesized in cell nuclei by host cell ____ ____ __.
These genomes must be exported where for assembly? Because of cellular regulations preventing unspliced RNA export from the nucleus; ____ _____ _____ must be encoded to promote their export. What is an example?
unspliced; RNA Pol II; the cytoplasm; viral RNA-binding proteins; HIV Rev1
Genomic segments are bound to NP as they are syn. and then by the M1 protein. What does this support? M1 containing RNP are directed to the exportin-1 pathway after binding a NEP that contains a ____ ____ ____
Ribonucleoprotein export; nuclear export signal
The NEP contains a C-terminal ___ _____ ____
M1 Binding domain
The M1 interacts with the membrane, cytoplasmic domains of HA and NA glycoproteins to initiate assembly and release of enveloped particles.
T
Retroviral proteins that mediate membrane association of genomic RNA are similar to _____ ______ of (-) strand RNA virus. Retroviral RNA is translated on ribosomes into ___. What does Gag transport?
matrix proteins; Gag; unspliced viral mRNA
