transposons
TRANSCRIPT
Ds is derived from Ac by internal deletions
Ds is not autonomous, requires Ac to move
Ac encodes a protein that promotes movement - Transposase
1942• Mcclintock’s discovery
1950 • TEs were discovered in fruit fly
1960 • E. coli
1970•Human genome
Triggering factors HSV,
EBV
HERV transactivation
Release of virions & Env protein
Super antigen-like activation
Breach of
BBB
? Multiple
Sclerosis
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, Alusite
• Appear to evolve from 7S RNA signal recognition particle
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
• Host modulation of TE movement• Methylation• Heterochromatin formation• piRNA
How do organisms live with TEs?
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)
• TEs can provide advantages and can be exploited by anorganism like human for his use !
How do organisms live with TEs?