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Einführung in die Genetik
Prof. Dr. Kay Schneitz (EBio Pflanzen)
http://plantdev.bio.wzw.tum.de
[email protected]
Prof. Dr. Claus Schwechheimer (PlaSysBiol)
http://wzw.tum.de/sysbiol
[email protected]
Einführung in die Genetik - Inhalte
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Einführung
Struktur von Genen und Chromosomen
Genfunktion
Transmission der DNA während der Zellteilung
Vererbung von Einzelgenveränderungen
Genetische Rekombination (Eukaryonten)
Genetische Rekombination (Bakterien/Viren)
Rekombinante DNA-Technologie
Kartierung/Charakterisierung ganzer Genome
Genmutationen: Ursache und Reparatur
Veränderungen der Chromosomen
Genetische Analyse biologischer Prozesse
Transposons bei Eukaryonten
Regulation der Genexpression
Regulation der Zellzahl - Onkogene
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20. 10. 15
27. 10. 15
03. 11. 15
10. 11. 15
17. 11. 15
24. 11. 15
01. 12. 15
08. 12. 15
15. 12. 15
22. 12. 15
12. 01. 16
19. 01. 16
26. 01. 16
02. 02. 16
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Regulation of Gene
Expression
Genetics 14
• Cells respond to intrinsic and extrinsic signals by modulating
Summary
transcriptional control of certain genes
• Gene activity is the result of the function of cis- and trans-acting
factors
• Trans-acting proteins react to environmental signals by using built-in
sensors that continually monitor cellular conditions
• Coordinated gene regulation in bacteria
• genes are often clustered into operons on the chromosome and
transcribed together as multigenic mRNAs
• one cluster of regulatory sites per operon is sufficient to
regulate expression of several genes
• Negative vs positive regulation
• repressor proteins bind to DNA at operator site thereby
blocking transcription (e.g., lac operon)
• activator proteins activate transcription by binding to DNA at
the promoter region (e.g., cAMP/CAP regulation of lac operon)
• Molecular anatomy of genetic switch
• regulatory proteins have DNA-binding domains (e.g., HLH) and
protein-protein interaction domains (modular
• specificity of gene regulation depends on specific protein-DNA
interactions mediated by the chemical interactions between aa
side chains and chemical groups of DNA bases
Summary
• Eukaryotic gene regulation resembles bacterial gene regulation
• trans-acting factors binding to cis-regulatory elements on the
DNA
regulatory factors determine the level of transcription by
• this
regulating the binding of RNA pol II to the promoter of a gene
• Enhancers/UAS
• cis-regulatory elements, possibly located quite far away (>10-50kb)
from promoter
• combinatorial interactions among different transcription factors
complexes of regulatory proteins that interact in
• enhanceosome:
cooperative and synergistic fashion --> high levels of transcription
through recruitment of RNA pol II
• Gene regulation and chromatin
• eukaryotic genes are packed in chromatin
• activation/repression requires specific modifications to chromatin
• genes are mostly turned off and kept silent in part by nucleosomes
and condensed chromatin
• histone code: pattern of posttranslational modifications of histone
tails (acetylation, methylation, phosphorylation etc).
• histone code is an epigenetic mark involved in nucleosome
positioning and chromatin condensation that can be altered by TFs
recruit for example ATP-dependent chromatin remodelers
• TFs
(e.g., SWI-SNF)
Control of cell number oncogenes
Genetics 15
Tumors
The cell cycle
The ubiquitin-proteasome system
Apoptosis
Cancerogenesis
Tumors
uncontrolled cell divisions and growth
invasion and colonization of tissue
malignant vs. benign tumors
metastasis
Tumor types
carcinoma - epithelial cell cancer
sarcoma - connective tissue or muscle cancer
leukemia or lymphoma - blood cell cancers
others
Tumors - incidence rates
Tumors - types and distribution
The cell cycle
Cell cycle studies
FACS sorting (fluorescence activated cell sorting)
Cell cycle studies
Northern blot
Western blot
Cell cycle mutants of yeast
Temperature sensitive mutants in cell cycle analysis
Major check points in cell cycle control
Cell cycle studies
Northern blot
Western blot
Cyclins and cyclin-dependent kinases are
differentially transcribed throughout the cell cycle
Cyclins and cyclin-dependent kinases (CDKs)
Cyclin-CDK
Complex
! Vertebrates
!
!Cyclin ! Cdk !
!
Yeast!
!Cyclin ! Cdk!
G1-Cdk !
G1/S-Cdk
S-Cdk !
M-Cdk !
!Cyclin D
!Cyclin E!
!Cyclin A !
!Cyclin B!
!Cln3
!
!Cln1,2 !
!Clb5,6 !
!Clb1,2,3,4
Cdk4, Cdk6
Cdk2 !
Cdk2 !
Cdk1 !
Cdk1!
Cdk1!
Cdk1!
Cdk1!
Cyclin-CDK complexes control the cell cycle
Mitosis promoting factor and cyclins
Cell cycle control by Cyclin-CDKs
Cell cycle control by Cyclin-CDKs
Cyclins and CDKs in cell cycle control
Mitotic cyclins and protein phosphorylation
The ubiquitin-proteasome system
and protein degradation
The ubiquitination machinery
E1 ubiquitin activating emzyme
E2 ubiquitin conjugating emzyme
E3 ubiquitin ligase
The ubiquitination machinery
The 26S proteasome
Mitotic cyclins and protein degradation
The anaphase promoting complex (APC)
Cancerogenesis
Major check points in cell cycle control
Examples for receptors in signaling
Receptor tyrosine kinases
JAK/STAT pathway
Receptor tyrosine kinases
Growth factors (EGF, TGF etc.)
Ras
Ras
The Retinoblastoma (RB) tumor suppressor
Retinoblastoma protein (Rb) blocks E2F
Prelavance of p53 tumour-suppressor mutations
p53 is phosphorylated in response
to DNA damage
p53 phosphorylation blocks the cell cycle
p53 phosphorylation blocks the cell cycle
p53 +/+
days
Mutations can induce cancer
Ras
Rb
p53
Summary
• Tumours are the result of uncontrolled
and invasive cell divisions and cell
growth
• The cell cycle is governed by cyclins and
cyclin-dependent kinases
• Cyclins and cyclin-dependent kinases
are under transcriptional control
• Cyclins are degraded by the UPS
• E1, E2, E2 enzymes and ubiquitin
• 26S proteasome
• Apoptosis regulated cell number
• Apoptosis is a controlled process
• p53, RB and Ras are important cell cycle
regulators
The end