transposon and mechanisms of transposition
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Transposon and Mechanisms of Transposition. Transposon. DNA sequence that can move in the genome Also called mobile DNA element or transposable element “ selfish DNA ” --exist only to maintain themselves ? - PowerPoint PPT PresentationTRANSCRIPT
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Transposon and Mechanisms of Transposition
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Transposon
DNA sequence that can move in the genome Also called mobile DNA element or transposable element “selfish DNA”--exist only to maintain themselves ? Transposition: The process by which these sequences are copied and inserted into a new site in the genome Probably had a significant influence on evolution
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How transposon was found
1940s, Barbara McClintock discovered the first transposable element in maize, earned a Nobel prize in 1983.Late 1960s, transposition was also found in Bacteria.
Barbara McClintock http://en.wikipedia.org/wiki/Barbara_McClintock
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Two Categories
Lodish et al., Molecular Cell Biology, 7th ed. Fig 10-8
DNA transposons Retrotransposons
“cut-and-paste”
Most mobile elements in bacteriabacteria is DNA transposons
In contrast, most mobile elements in eukaryoteseukaryotes are retrotransposons, but eukaryotic DNA transposons also occur.
“copy-and-paste”
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DNA transposons
General structure of bacterial IS elementsLodish et al., Molecular Cell Biology, 7th ed. Fig 10-9
Bacterial Insertion Sequences (IS element)
P element in Drosophila
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Lodish et al., Molecular Cell Biology, 7th ed. Fig 10-10
General process of transposition for DNA transposons
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General structure of eukaryotic LTR retrotransposonsLodish et al., Molecular Cell Biology, 7th ed. Fig 10-11
Retrotransposons LTR retrotransposons:
Non-LTR retrotransposons: the most common type of transposons in mammals
What is the difference from retrovirus?What is the difference from retrovirus?
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Generation of RNA from LTR transposon
Lodish et al., Molecular Cell Biology, 7th ed. Fig 10-12
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Model for reverse transcriptionLodish et al., Molecular Cell Biology, 7th ed. Fig 10-13
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Retrotransposons Non-LTR retrotransposonsNon-LTR retrotransposons long interspersed elements (LINEsLINEs)
≈6 kb in human
account for 21% of the genome
short interspersed elements (SINEsSINEs)
≈300 bp in human
account for 13% of the genome
Lodish et al., Molecular Cell Biology, 7th ed. Fig 10-15
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General Principles of LINE transposition
Lodish et al., Molecular Cell Biology, 7th ed. Fig 10-16
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SINEs (Short Interspersed Elements)
Weiner (2000) Fig 1
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Most are tRNA derived; Alu is 7SL-RNANonautonomousDependent on other machinery- genome “parasite” RNA Pol IIINeeds LINE Endonuclease and Reverse Transcriptase for activity
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Average size 150-200 base pairs
Composed of 3 parts 5’ head Body 3’ tail
Vassetzky (2013)
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http://biol.lf1.cuni.cz/ucebnice/images/rep1.gif
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Kramerov & Vassetzky (2005)
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Transport
Kramerov & Vassetzky (2005)
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Batzer & Deininger, Nature Reviews Genetics (2002) Box 1
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Kramerov & Vassetzky (2005)
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“Transposons: Mobile DNA” (2012)
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Where there is a SINE, there is a LINESpecificity of EN/RT of LINE dictates locationExpressed during early embryogenesis and decreases in developmentActive in tumor cellsIntegrates into germ lines
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References Batzer, M.A. & Deininger, P.L. Alu repeats and Human genomic diversity. Nature Reviews Genetics 3,
370-379 (2002). Doi:10.1038/nrg798 http://www.nature.com/nrg/journal/v3/n5/box/nrg798_BX1.html
Kramerov, D.A. & Vassetzky, N.S. Short Retroposons in Eukaryotic Genomes. International Review of Cytology, vol 247 (2005) doi: 10.1016/S0074-7696/05
Lodish et al., Molecular Cell Biology, 7th ed.
“Transposons: Mobile DNA”. (2012) http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Transposons.html
Vassetzky. SINEBase (2013) http://sines.eimb.ru
Weiner, A. Do all SINEs lead to LINEs? Nature Genetics 24, 332-333 (2000) doi:10.1038/74135http://www.nature.com/ng/journal/v24/n4/full/ng0400_332.html