The CTCF Insulator Protein Is Posttranslationally Modified by SUMO
V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.
-
Upload
madlyn-stewart -
Category
Documents
-
view
214 -
download
0
Transcript of V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.
![Page 1: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/1.jpg)
V(D)J Recombination and the Role of CTCF
Richard Wolfe; Xinhao Liu
![Page 2: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/2.jpg)
T cell
T cell
1.A sort of lymphocytes
2.Related to Cell mediated immunity
3.Have T Cell recepor(Tcr) on the surface
![Page 3: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/3.jpg)
B cell
B cell
1.A sort of lymphocytes
2.Related to humoral immunity
3.Have Bcr on the surface
4.Make antiboty
![Page 4: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/4.jpg)
Light chain
Heavy chain
![Page 5: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/5.jpg)
What is VDJ Recombination?
• V(D)J recombination is Somatic rearrangement of variable (V), diversity (D) and joining (J) regions of the genes that encode antigen receptors, leading to repertoire diversity of immunoglobulins and T cell receptors.
![Page 6: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/6.jpg)
The structure of antigen receptor genes
Immunoglobulin
Heavy chain
Light chain
T cell receptor
Beta-chain
Alpha and d chain
![Page 7: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/7.jpg)
Initiation of Recombination
• RAG(RAG recombinase) is a protein complex encoded by genes RAG1 and RAG2
HMGB1 or HMGB2 bind Spacers
![Page 8: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/8.jpg)
![Page 9: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/9.jpg)
Order during VDJ recombination
1. lgh and Tcrb are assembled with D to J recombination preceding V to DJ recombination
2. Immunoglobulin light chain(lgk or lgl) or Tcra is initiated.
Allelic exclusion: lg loci recombine full only in B cell lineage and TRC loci recombine only in T cells.
Question: How are the order, fidelity and allelic exclusion regulated during VDJ recombination?
![Page 10: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/10.jpg)
Answer
Antigen receptor locus architecture and nuclear location work together with locus accessibility to ensure order, fidelity and allelic exclusion during the VDJ recombination
![Page 11: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/11.jpg)
Character of Accessibility
V(D)J recombination correlates with numerous markers of open chromatin,germline transcription, activating histone modifications, nuclease accessibility and DNA hypomethylation, which indicate a tight connection between chromatin structure and targeting of recombination.
Character of Inaccessibility
1. A high nucleosome density, which affects direct positioning of RSSs on nucleosomes, cause steric constraints by nucleosome packing.
2. Deletion of enhancer accompanied by a loss of germline transcription
3. Deletion of promoter which has a more local effect.
4. antisense transcription
![Page 12: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/12.jpg)
There are many other regulation of VDJ recomnination.
• CTCF, H3K9, H3K4, transcription factor, chromatin remodeling complex
![Page 13: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/13.jpg)
CTCF as Repressor or Activator
• CTCF – CCCTC Binding Factor• Connects and separates different
chromatin domains through loop formation
• Mouse embryonic stem cells
• Four Types of Domains:
I. Formation of active domain
II. Formation of repressive domain
III. Formation of enhancer-promoter
IV. Formation of domain barrier between active and inactive chromatin regions
![Page 14: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/14.jpg)
CTCF and the architecture of the Igh locus• Igh locus – V(D)J recombination• Heavy chain locus• Cohesin is a CTCF cofactor• Pre-proB stage is D-J recombination• ProB stage V-DJ recombination
a. CTCF and Cohesin binding sites• Cohesin binding at CTCF-sites more
specific pattern in proB stage
b. PAIR – Pax5-activated intergenic repeat elements
• PAIR elements bind with CTCF and mediate changes in locus conformation essential for V-DJ recombination
c. Pre-proB stage, CTCF bound to CB1/2 acts as an insulator, which stops antisense transcription and active chromatin from D spreading to V, thus limiting D-J recombination. In proB stage the barrier is released allowing V-DJ recombination
d. Model of CTCF mediated loops at preB stage assisting D-J recombination and at proB assisting V-DJ recombination
![Page 15: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/15.jpg)
CTCF/Cohesin and the Igk and Tcra loci • Igk locus – VJ
recombination• Light chain locus• Tcra loci – T cell
a. CTCF binding more specific in preB cells
• Enlarged area shows CTCF site in Sis silencer as in igh locus
b. Approx. 60 CTCF binding sites of High and Low occupancy in V region
• Model shows CTCF loop separating enhancers from the V region
c. Again, CTCF binding site at TEA act to insulate the C-Jx region from the Dad1 area and Tcrd area
![Page 16: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/16.jpg)
Conclusion
• CTCF and its cofactor, cohesin, have a fundamental role in regulating locus conformation and V(D)J rearrangement of the antigen receptor loci.
![Page 17: V(D)J Recombination and the Role of CTCF Richard Wolfe; Xinhao Liu.](https://reader035.fdocuments.us/reader035/viewer/2022062518/5697bf9a1a28abf838c9266e/html5/thumbnails/17.jpg)
References
• Images:• Chaumeil J, Skok J: The role of CTCF in regulating
V(D)J recombination. Current Opinion in Immunology 2012, 24:153-159.
• Image of T cell, B cell and anti body are from google.• Image of recombination process are from David G.
Schatz* and Yanhong Ji, Recombination centres and the orchestration of V(D)J recombination. NATURE REVIEWS | IMMUNOLOGY 2011,11:251-263