Molecular Biology Fourth Edition. Copyright © The McGraw-Hill Companies, Inc. ... Lodish et al., Molecular Cell Biology, 7th ed. Fig 10-8. â DNA transposons.
Lecture10 Transposon and Mechanisms of Transposition •Molecular Genetics I: MLGN 301 2016 7/12/2016 By Prof.Dr /Ahmed Mansour Alzohairy
Genetics Department, Zagazig University, Zagazig, Egypt
Learning objectives
Learning about: -
Transposon Mechanisms of Transposition Retrotransposons SINE and LINE
Robert F. Weaver. Molecular Biology Fourth Edition. Copyright © The McGraw-Hill Companies, Inc.
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Learning outcomes By the end of this session and practical, students are expected to be able to understand what are: - The mobile DNA element or transposable element - DNA transposons & Retrotransposon - General Principles of LINE transposition - Generation of RNA from LTR transposon - the difference from retrovirus Robert F. Weaver. Molecular Biology Fourth Edition. Copyright © The McGraw-Hill Companies, Inc.
3-3
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
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 Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
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
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
“We know about the components of genomes that could be made available for such restructuring. We know nothing, however, about how the cell senses danger and instigates responses to it that are often truly remarkable” McClintock, B. (1984) Science 226, 792–801.
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Two Categories DNA transposons Retrotransposons “cut-and-paste”
“copy-and-paste”
Most mobile elements in bacteria is DNA transposons In contrast, most mobile elements in eukaryotes are retrotransposons, but eukaryotic DNA transposons also occur. Lodish et al., Molecular Cell Biology, 7th ed. Fig 10-8
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Class1
Class2
Retrotransposon
Transposon
DNA transposons Bacterial Insertion Sequences (IS element) P element in Drosophila
General structure of bacterial IS elements Lodish et al., Molecular Cell Biology, 7th ed. Fig 10-9
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
General process of transposition for DNA transposons
Lodish et al., Molecular Cell Biology, 7th ed. Fig 10-10
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Retrotransposons LTR retrotransposons: Non-LTR retrotransposons: the most common type of transposons in mammals
General structure of eukaryotic LTR retrotransposons Lodish et al., Molecular Cell Biology, 7th ed. Fig 10-11
What is the difference from retrovirus?
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Generation of RNA from LTR transposon
Lodish et al., Molecular Cell Biology, 7th ed. Fig 10-12
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
What is the difference from retrovirus?
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Model for reverse transcription Lodish et al., Molecular Cell Biology, 7th ed. Fig 10-13
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Model for reverse transcription Lodish et al., Molecular Cell Biology, 7th ed. Fig 10-13
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Retrotransposons • Non-LTR retrotransposons
long interspersed elements (LINEs) ≈6 kb in human account for 21% of the genome short interspersed elements (SINEs) ≈300 bp in human account for 13% of the genome
Lodish et al., Molecular Cell Biology, 7th ed. Fig 10-15
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
General Principles of LINE transposition
Lodish et al., Molecular Cell Biology, 7th ed. Fig 10-16
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
SINEs (Short Interspersed Elements)
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy Weiner (2000) Fig 1
Most are tRNA derived; Alu is 7SL-RNA Nonautonomous Dependent on other machinery- genome “parasite” RNA Pol III Needs LINE Endonuclease and Reverse Transcriptase for activity Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Average size 150-200 base pairs Composed of 3 parts 5’ head Body 3’ tail
Molecular Genetics I: MLGN 301 2016 name: Prof. Ahmed Mansour Alzohairy VassetzkyTrainer (2013)
Molecular Genetics I: MLGN 301 2016 http://biol.lf1.cuni.cz/ucebnice/images/rep1.gif
Trainer name: Prof. Ahmed Mansour Alzohairy
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy Kramerov & Vassetzky (2005)
Transport
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy Kramerov & Vassetzky (2005)
Molecular Genetics I: Batzer MLGN 301 2016 & Deininger, Nature Reviews Trainer name: Prof. Ahmed Mansour Alzohairy Genetics (2002) Box 1
Kramerov & Vassetzky (2005)
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Molecular Genetics I: MLGN 301 2016 “Transposons: Mobile DNA” (2012)
Trainer name: Prof. Ahmed Mansour Alzohairy
Where there is a SINE, there is a LINE Specificity of EN/RT of LINE dictates location Expressed during early embryogenesis and decreases in development Active in tumor cells Integrates into germ lines
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
References •
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Batzer, M.A. & Deininger, P.L. Alu repeats and Human genomic diversity. Nature Reviews Genetics 3, 370379 (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:10.1038/74135 http://www.nature.com/ng/journal/v24/n4/full/ng0400_332.html
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Practical (to try in your own time)
Explain with drawing the differences between the two Categories of mobile DNA element ?
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Molecular Genetics I: MLGN 301 2016 Trainer name: Prof. Ahmed Mansour Alzohairy
Department of Genetics, Zagazig University, Zagazig, Egypt