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non-enveloped, dsDNA viruses
belong to the adenoviridae family
moderately sized (around 100 nm)
adenoviruses
have fibers that protrude from the five-
fold axis of symmetry and play a role in
viral binding to the host cell receptors
linear, dsDNA genome
coordinate expression of genes in
similar fashion to what is done by
herpes and pox viruses
genes on the left side of the genome are
transcribed first, and then these
genome structure of adenoviruses transcripts and resulting proteins are
used for expression of genes further
down the genome
the first viral gene to be transcribed, and
one of the first to be used in replication
is the E1A gene’ it’s protein product has
two functions
, promotes transcription of other viral
genes
similar to herpes and pox viruses
bind to specific host cell proteins that
regulate the growth cycle of that cell
the results of interacting with
this protein is that it essentially
two functions of E1A protein product locks the cell in a DNA synthesis
phase, which is an advantage for
a dsDNA virus
the specific role this gene plays in viral
replication makes it critical for
controlling replication, and so it is one
of the genes that is modified in
adenoviruses that are being used as
gene therapy vectors
, another gene that is often modified and
actually deleted in adenovirus gene
therapy vectors
expressed very late in replication, and
E3 gene doesn’t play a critical role in the early
stages of infection like the E1A gene
the non-critical nature of the gene is
useful when generating viruses to be
used in gene therapy
infectious cycle begins with binding of
characteristic protruding fibers on the
surface of the virus to its host cell
these viruses bind the same
receptor as coxsackie viruses,
and the receptor is named
coxsackie-adenovirus receptor
(CAR)
after binding, the virus moves along the
surface of the cell until it comes in
adenovirus attachment and entry
contact with a clathrin-coated pit, and
enters through clathrin-mediated
endocytosis
once inside the vesicle, the protrusions
are no longer present, and the base of
the fiber (the penton) interacts with the
cellular protein on the inside of that
endoscopic vesicle (the integrin)
this interaction begins the disassembly
process for the viral capsud
adenovirus replication the virus continues to uncoat as it
moves through the cytoplasm, and
ultimately the genome is imported into
the nucleus
at this point, the host cell pols being
transcribing the immediate early gene
E1A
these mRNAs are spliced and
transported to the cytoplasm, where the
E1A protein gets made
these proteins then migrate back into
the nucleus, where they regulate both
cellular and viral genes