Transposons jumping genes

1. Transposons

2. Outline
Discovery
Types
Mechanism of transposition
Role
•Evolution
•Gene therapy

3. Selfish DNA
Jumping
genes
Genomic
parasite

5. • Some transposable elements are introns
• Not all introns are TE.

6. •Transposable elements are DNA sequences that move from
one location on the genome to another.

7. Maize / Corn

8. Why are these kernels spotted ?

10. 10

11. 11

12. 12

13. Somatic Excision of Ds from C
Fig. 23.9
SectoringWild type

14. Ds is derived from Ac by internal deletions
Ds is not autonomous, requires Ac to move
Ac encodes a protein that promotes movement - Transposase

15. 1942
• Mcclintock’s discovery
1950 • TEs were discovered in fruit fly
1960 • E. coli
1970
•Human genome

16. Thanks to transposons

17. Before Mcclintock
genes have fixed location
After Mcclintock
genes can move

18. After 40 long years

19. Types of Transposons
Type II
Type I

20. Transposons
Type IIType I
LTR
Non-LTR

21. Diversity of transposons

23. MechanismOf DNA Transposons

25. Target Site Duplication
MechanismOf DNA Transposons

26. How does copy number increase ?

27. How does copy number increase ?

28. How does copy number increase ?

29. Can reach high
numbers in the
genome because of
replicative movement.
Retro-Transposons
Type I

35. Our genome is NOT only ours !
Our genome contains virus !!!!!!

36. HERV - K

37. Triggering
factors HSV,
EBV
HERV transactivation
Release of virions & Env protein
Super antigen-like activation
Breach of
BBB
? Multiple
Sclerosis

38. LINES & SINES
• LINES-Long Interspersed Nuclear
Elements
• About 868,000 in human genome
• 6,500 base pairs long including LTRs
• Encode reverse transcriptase and integrase
• Copy-paste mechanism to insert elsewhere
• SINES-Short Interspersed Nuclear
Elements
• Millions in human genome
• 100-400 bases long
• Often contain RNA polymerase III promoters
but no genes
• ALUs- The most common SINE
• 1,500,000 copies = 11% of human genome
• 350 base pairs in length
• Contain an RNA Polymerase III promoter, Alu
site
• Appear to evolve from 7S RNA signal
recognition particle

40. LINE

41. LINE

42. LINE

43. LINE

44. SINE needs LINE

45. Sorghum 700 Mb
Barley 5,000 Mb
Maize 2,500 Mb
Oats ~20,000 MbWheat 20,000 Mb
Rice 450 Mb
Variation in cereal genomes - transposons & genome
duplications

46. • Most TEs are inactive - fossils
How do organisms live with TEs?

47. How do organisms live with TEs?
•Active TEs evolved to insert into safe sites.

48. Alu within the Alu
Full Alu sequence
½ Alu sequence
½ Alu sequence

49. • Host modulation of TE movement
• Methylation
• Heterochromatin formation
• piRNA
How do organisms live with TEs?

50. SINEs – short
interspersed nuclear
elements (eg Alu)
Transposable element (TE) content of human genome
Alu repeats: ~300 bp long
with AluI restriction site, > 1
million copies in human
genome
SVA composite
retroelement (SINE,
VNTR & Alu)
LINEs – long
interspersed nuclear
elements (eg L1)

52. Alu
family

53. Target
primed
reverse
transcription
(TPRT)

54. • TEs can provide advantages and can be exploited by an
organism like human for his use !
How do organisms live with TEs?

55. Evolution of Placental Mammals

56. Obstacle is xenotransplantation

58. Methods for detecting transposons insertions

59. Transposon
tagging