Retrovirus: Partikkel, genom og proteiner
Figure 1 Retroviral particle and genome
structure. (a) Retrovirus particle showing
the approximate location of its
components using the standardized twoletter nomenclature for retroviral
proteins. (b) Genome organization and
gene expression pattern of a simple
retrovirus, showing the structure of an
integrated provirus linked to flanking host
cellular DNA at the termini of its LTR
sequences (U3-R-U5) and the full-length
RNA that serves as genomic RNA and as
mRNA for translation of the gag and pol
ORFs into polyproteins. env mRNA is
generated by splicing and encodes an Env
precursor glycoprotein. LTR, long terminal
repeat (U3-R-U5 for proviral DNA, derived
from R-U5 downstream of 5′ cap and U3R upstream of 3′ poly(A) in genome
RNA); PBS, primer binding site; Ψ,
packaging signal; PPT, polypurine tract;
SD, splice donor site; SA, splice acceptor
site.
Retrovirus: Replikasjonssyklus
Figure 2 Replication cycle
of a simple retrovirus. The
flow of the early part of the
replication cycle goes from
receptor binding and
internalization at the left
through reverse
transcription to integration
of the proviral DNA. The
late part of the replication
cycle proceeds from the
provirus through
transcription and
processing and translation
of viral RNA to assembly
and release of viral
particles. Maturation of the
released particles involves
cleavage of viral
polyproteins by PR
(protease).
Strukturen av HIV revers
structure of
transkriptase X-Ray
HIV-1 reverse
transcriptase. (a)
tube-and-arrow
representation of the
p66 subunit’s
polymerase
domain.(b) The p51
subunit with its pink
palm subunit oriented
identically to that in
p66.(c) A ribbon
diagram of the HIV-1
RT p66/p51
heterodimer in
complex with DNA.
Reaksjoner som katalyseres av
revers transkriptase
Revers transkripsjon av genomisk
RNA
Figure 3 Reverse
transcription and integration
processes. (a) Reverse
transcription. Outline of the
reverse transcriptase (RT)catalysed steps leading from
single-stranded genomic RNA
(top; black line) to doublestranded proviral DNA
(bottom; red line). (b)
Integration. The viral DNA
(top) is the product of the
completed reverse
transcription process of (a).
Shown are the integrase (IN)mediated cleavage and
religation steps leading to
joining of proviral and host
DNA. Subsequent repair and
ligation are carried out by
host factors. Note the loss of
two terminal nucleotides of
the viral DNA and the
generation of a short repeat
of host sequences of the
integration site.
Retrovirus
replication carried
out by reverse
transcriptase
Retrovirus
replication carried
out by reverse
transcriptase
Retrovirus
replication carried
out by reverse
transcriptase
Bakteriekromosomet: protein
HU
Metafasekromosom
Encyclopedia of Life Sciences / www.els.net
Nature Publishing Group ©2001 Macmillan Publishers Ltd.
Page 1423
Electron micrograph of a human
metaphase chromosome.
Page 1423
Thin section through a cell nucleus
treated with Feulgen reagent
Page 1423
Calf Thymus Histones
Page 1424
The amino acid sequence of
calf thymus histone H4
. The protein’s 25 Arg and Lys residues are indicated in red. Residues that can be
covalently modified are underscored. The two positions where there are
differences between H4 from calf and pea are boxed (Val60 →Ile, Lys77 → Arg).
Nukleosomstige
Min
0 3 6 10 20 30
Page 1424
Electron micrograph of D. melanogaster
chromatin showing that its 10-nm fibers are
strings of closely spaced nucleosomes.
Page 1425
Defined lengths of calf thymus chromatin.
(a) Electron micrographs fractions containing
nucleosome monomers, dimers, trimers, and
tetramers.
Page 1425
Defined lengths of calf thymus chromatin.
(b) Gel electrophoresis of DNA extracted from the
nucleosome multimers are multiples of ~200 bp.
Page 1425
SDS–gel electrophoresis of a mixture of calf
thymus histones H3 and H4 cross-linked by
dimethylsuberimidate.
Page 1426
X-Ray structure of the nucleosome core
particle. (a) The entire core particle as
viewed (left) along its superhelical axis and
(right) rotated 90° about the vertical axis.
Page 1426
X-Ray structure of the nucleosome core particle.
(b) The top half of the nucleosome core particle as
viewed in Part a, and identically colored.
Nukleosomer
Nukleosom
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The histone fold
Encyclopedia of Life Sciences / www.els.net
Nature Publishing Group ©2001 Macmillan Publishers Ltd.
Page 1427
X-Ray structure of a histone octamer
within the nucleosome core particle.
Histonmodifisering
Nukleosom og histonhaler
Encyclopedia of Life Sciences / www.els.net
Nature Publishing Group ©2001 Macmillan Publishers Ltd.
Page 1427
Model of the interaction of histone H1 with
the DNA of the 166-bp chromatosome.
Page 1428
Electron micrographs of chromatin. (a)
H1-containing chromatin and (b) H1depleted chromatin, both in 5 to 15 mM salt.
Page 1429
Electron micrograph of the 30nm chromatin filaments.
Kromatinstruktur
Page 1430
Model of the 30-nm chromatin filament. The
filament is represented (bottom to top) as it might
form with increasing salt concentration.
Page 1430
Electron micrographs of a histonedepleted metaphase human chromosome.
(a) The central protein matrix (scaffold) serves to anchor the surrounding DNA.
Page 1430
Electron micrographs of a histone-depleted
metaphase human chromosome.
(b) At higher magnification it can be seen that the DNA is attached to the scaffold in loops.
Page 1431
Organization of DNA in a
metaphase chromosome.
(a) Electron micrograph of a human metaphase chromosome in cross section.
Page 1431
Organization of DNA in a
metaphase chromosome.
(b) Diagram showing how the radial loops are thought to combine with the scaffold.
Pakking av DNA i kromosomer
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Nature Publishing Group ©2001 Macmillan Publishers Ltd.
The histone gene cluster
Høyere ordens
kromatinstruktur:
Binding av DNA
til kjernematriks