Transcript Immunoglobulin Gene Rearrangement et hz js 113016

Immunoglobulin Gene
Rearrangement
Eliza Thapa
Huizhi Zhao
Jingwen Song
General Outline
Introduction to immunoglobulin and V(D)J
recombination
Mechanism of V(D)J recombination
Effect of V(D)J recombination
Immunoglobulin (Ig)
http://factfile.org/wp-content/uploads/2015/03/Antibodies-Image.jpg
• serum glycoprotein produced by B cells against foreign molecules
• foreign molecules- antigen (bacteria, virus, pollens etc)
• antibody binds to specific antigen
• occurs in two forms- soluble form
- Membrane bound form (BCR)
Structure of Immunoglobulin
• 2 heavy chains (H)
•2 light chains (L)
•H and L linked by disulfide
bonds
•Two (H-L) chain linked by
disulfide bond
• amino terminal variable (V)
region
•Carboxyl- terminal constant (C)
region
www.namrata.co/wp-content/uploads/2012/04/immunoglobulinsstructure.jpeg
Types of Immunoglobulin
Five classes of immunoglobulins
•Immunoglobulin D (δ)
•Immunoglobulin E (ε)
•Immunoglobulin G (γ)
•Immunoglobulin M (μ)
•Immunoglobulin A (α)
Not found in humans
•Immunoglobulin Y
•Immunoglobulin W
http://www.nature.com/nrm/journal/v3/n12/box/nrm972_BX1.html
Means of Ig Diversity
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Multiple germ-line gene segments
Combinatorial V-(D)-J joining
Junctional flexibility
P-region nucleotide addition
N-region nucleotide addition
Somatic hypermutation
Combinatorial association of light and heavy chains
Combinatorial V-(D)-J joining
http://www.microbiologybook.org/mayer/gen-1.jpg
V(D)J recombination occurs during B-Cell Development
Light chain Gene rearrangement
Heavy chain gene rearrangement
How much variation is possible through
recombining gene fragments?
•Over 1.5*107combinations of variable, diversity and joining gene segments are
possible.
•Imprecise recombination and mutation increase the variability into billions of
possible combinations
Mechanism of Rearrangement
• Recombination Signal Sequences (RSSs).
• Recombination Activating Genes: RAG-1 and
RAG-2.
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Recombination Signal Sequence
• A short DNA sequence indicate
the sites of recombination
• seven conserved nucleotides (a
heptamer) that reside next to
the gene encoding sequence
• a spacer (containing either 12
or 23 unconserved nucleotides)
• a conserved nonamer (9 base
pairs)
Nature Reviews Immunology 11, 251-263 (April 2011)
Nature Reviews Immunology 11, 251-263 (April 2011) | doi:10.1038/nri2941
Recombination Signal Sequence
• Two types of RSS exist
• Each V, D, or J gene segment is flanked by RSS
• The RSSs are present on the 3’ side (downstream) of a V region and the
5’ side (upstream) of the J region
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http://biosiva.50webs.org/immunediversity.htm
Recombination Activating Gene
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RAG enzymes work as a multi-subunit complex to induce cleavage of a single
double stranded DNA (dsDNA) molecule between the antigen receptor coding
segment and a flanking recombination signal sequence (RSS).
Schatz, David G., and Patrick C. Swanson. "V (D) J recombination: mechanisms of initiation." Annual review of genetics 45 (2011): 167-202.
V(D)J recombination:
(1) a complex containing RAG1 and RAG2 binds one
RSS.
(2) This RAG-RSS complex then captures the
second RSS (of the gene segment to be joined)
in a process known as synapsis.
(3) Cleavage by RAG1/2 occurs between the RSS
heptamer and flanking coding sequence, and
proceeds in two steps. A nick is made at the 5’
end of the RSS heptamer. The second step is a
hairpinning step joining the 3’-hydroxyl to the
phosphoryl group at the same nucleotide
position on the other strand.
(4) DNA cleavage is completed within the synaptic
complex.
(5) The product of this first phase of V(D)J
recombination is the “cleaved signal complex,”
which contains four DNA ends: two blunt 5’phosphorylated signal ends, and two coding
ends terminating in DNA hairpin structures.
Nature Reviews Immunology 8, 302-312 (April 2008)
V(D)J recombination:
During the second phase of V(D)J
recombination, RAG1 and RAG2 work
together with DNA repair proteins to
process and ligate coding ends to form
a coding joint, and ligate signal ends to
form a signal joint.
This phase requires ubiquitously
expressed DNA repair factors of the
non-homologous end joining (NHEJ)
pathway.
Nature Reviews Immunology 8, 302-312 (April 2008)
Products of V(D)J recombination:
Roth, David B. "V (D) J Recombination: Mechanism, Errors, and Fidelity."Microbiology Spectrum 2.6 (2014).
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V(D)J Recombination Errors:
The two types of V(D)J recombination errors:
Errors in Target Recognition
Errors in End Joining
Errors in Target Recognition:
 In lymphoid neoplasms
 cryptic RSS(CRSS) ： cRSSs
capable
of
supporting
recombination
are
present
approximately once per kilobase in random DNA sequences
 small size of RSS sequences;
strict
adherence
of
this
sequence
to
consensus
heptamer or nonamer sequence
 mismatching of RSSs and cRSSs
that are adjacent to protooncogenes
Roth D. 2014. V(D)J Recombination: Mechanism, Errors, and Fidelity
Errors in Joining:
A pair of breaks created during
normal V(D)J recombination are
mistakenly joined to another
break created by another
mechanism
Errors in joining involve events
that join a RAG-mediated doublestrand break to a broken DNA end
created by a non-RAG-mediated
mechanism
Roth D. 2014. V(D)J Recombination: Mechanism, Errors, and Fidelity
Summary
• 1. V(D)J Recombination provide a method to
create an almost limitless supply of different
antibodies to target antigens associated
with pathogens
• 2.Aberrent V(D)J Recombination like errors
in target recognition and errors in End
Joining, can play important roles in
initiating oncogenic transformation
Reference
• https://www.youtube.com/watch?v=QTOBSFJWogE
• Roth D. 2014. V(D)J Recombination: Mechanism, Errors,
and Fidelity
• Nature Reviews Immunology 8, 302-312 (April 2008)
• Schatz, David G., and Patrick C. Swanson. "V (D) J
recombination: mechanisms of initiation." Annual review
of genetics 45 (2011): 167-202.