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Régulation génique par les microARNs
Gene regulation by microRNAs
Martin Simard Ph.D.Oncologie-CRCHU de Québec (Hôtel-Dieu de Québec)Centre de Recherche sur le cancer de l’Université Laval
• Discovery of microRNA (small temporal RNA)
• Example of function
• microRNA and Cancer
• microRNA and therapy
• Where they come from?
• Biogenesis of microRNA
• Regulation of the microRNA pathway
• Regulation of gene expression
Outlines
microRNAs: a very unique class of
gene uncovered in 1993
• Control developmental timing in specific cells and thus, insure the p r o p e r a n i m a l development. lin-4
lin-14
lin-28
Lee et al, Cell
Wightman et al, Cell
egg
L1
L2L3
L4
Adult
Heterochronic genes
• Gene that does not code for any protein
• 21 nucleotides long RNA
• Abrogates protein synthesis
• Partially complementary to its target RNA
Well! A weird phenomenon only seen in worms!
lin-4: A very special gene
Pasquinelli et al, Nature, 2000
A second example: let-7
Science, 2001
2001: More than 100 are identified
Major breakthrough
• C. elegans: Development, neuronal asymmetry
• Fruit fly: Apoptosis, cell proliferation
• Plants: leaves and flowers morphogenesis
• Vertebrates: Brain morphogenesis, hematopoiesis, neuronal and heart development
Over 10 000 microRNAs to date
Precise expression profile
Pena et al, Nature Methods 2009
Precise expression profile: hematopoiesis
Gangaraju and Lin, Nature Reviews MCB 2009
The loss of microRNAs lead to fatality
Zhao et al, Cell 2007
Ventura et al, Cell 2008
Loss of miR-1-2 leads to
overproduction of muscle cells
Problème majeur dans la
formation de cellules B
Loss of miR-17-92 cluster is embryonic
lethal
microRNAs and Cancer
microRNAs are frequently located in altered genomic regions associated to various
cancers
Calin et al, PNAS 2004
Interaction between microRNAs with tumor suppressors and oncogenes
microRNAs are part of the chain of reaction leading to tumorigenesis
• microRNAs can regulates their expressions
• microRNAs can be regulated by tumor suppressors genes and oncogenes
p53, p21, PTEN, p27, etc
p53, MYC
MYC: a key transcriptional regulation of microRNAs
Nature Genetics, 2008
Interactions of microRNAs with MYC
Lujambio et al, Nature 2012
miR-34
BCL2 CDK4 CDK6CyclinE2
Cell proliferationSurvival
p53
He et al. Nature 2007 (+4)
Interaction of microRNAs with the p53 pathway
miR-34
BCL2 CDK4 CDK6CyclinE2
Cell proliferationSurvival
miR-16-1
miR-143
miR-145
p53
Suzuki et al. Nature 2009He et al. Nature 2007 (+4)
Interaction of microRNAs with the p53 pathway
Hermeking, Nat. Rev. Cancer 2012
Implication of the p53 pathway: Multiple levels
Interaction of microRNA with BRCA1
J. Cell Biology 2012
• Oncogenes
TumourSuppressor
Tumour
microRNAs and Cancer
Oncogene 2006
One example: miR-10b
Nature, 2007
microRNA as Oncogene : miR-10b
• Overexpression increases angiogenesis
• Induces metastasis formation
• Correlation between mir-10b overexpression and metastatic tumours caused by breast cancer
Ma et al, Nature 2007
Cancers tumors can become addicted to the overexpression of microRNAs: the miR-21 case
Medina et al, Nature, 2010
The overexpression of miR-21 in the
hematopoietic system lead to lymphoma
formation
Medina et al, Nature, 2010
Blocking miR-21 overexpression:
the tumors shrink!
Cancers tumors can become addicted to the overexpression of microRNAs: the miR-21 case
• Oncogenes
• Tumour suppressors
TumourSuppressor
Tumour
Oncogene
Tumour
microRNAs and Cancer
Oncogene 2006
microRNA as Tumour suppressor : let-7
• let-7 level is altered in lung cancer
• let-7 controls RAS expression
• HMGA2 is another target of let-7
Johnson et al, Cell 2005
Mayr et al, Science 2007
Nature, 2008
One example: miR-335 et miR-126
Tavazoie et al, Nature, 2008
Re-establishing their expressions diminish the metastasis formation
microRNA as Tumour suppressor : miR-335 and miR-126
miR-335 controls cell migration
miR-126 controls cell proliferation
Ventura and Jacks, Cell 2009
microRNAs and Cancer: more and more examples
A new term in medical biology: oncomiRs
microRNAs with altered expression in tumours leading to affect cellular transformation, carcinogenesis and metastases formation: oncogene and tumour suppressors.
Slack, Nature Rev. Cancer, 2006
Different ways microRNAs can lead to cancer
Lujambio et al, Nature 2012
microRNAs and Cancer: Metastase formation
Kasinski and Slack, Nat. Rev. Cancer 2011
Different expression profile between healthy and cancer tissue
samples
Lu et al, Nature 2005
microRNAs and Cancer: new biomarkers
microRNAs and Cancer: new biomarkers
Nature Biotechnology 2008
microRNAs and Cancer: new biomarkers
• Stable and easily detectable in body fluids
• Specific miRNA signature
Weber et al, Clinical Chemistry 2010
microRNAs and Cancer: new biomarkers
Cortes et al, Nat.Rev. Clinical Oncology 2011
Different ways to export microRNAs
Cortes et al, Nat.Rev. Clinical Oncology 2011
• Exosomes
• HDL
• Coupled with proteins
“field in progress”
Export of microRNAs: very promising research avenue
Nature 2015
microRNAs as biomarkers: Advantages
• Very efficient to distinguish different tissues and tumours
• Simpler to identify good biomarkers from a set of hundreds microRNAs than 40 000 mRNAs
• microRNAs are extremely stable
• This stability allows retrospective analyses with conserved tissues
• microRNA can be visualized in tissues and cells with conventional techniques
• Viral infections (Herpes virus, SV40, HIV)
- Viruses encodes microRNAs that target viral mRNAs to regulate various stages of the viral life cycle
- Viral microRNAs suppress expression of specific host genes
- Viral infections induce expression of host microRNAs that inhibits expression of cellular genes
- Upon viral infections, host cells express specific microRNA that suppress viral mRNA expression
• May be important for gene imprinting
• Cardiac, immune, neurological and metabolic disorders
microRNA pathway associated to various diseases
Viruses highjack host microRNAs Cazalla et al, Science 2010
• Herpesvirus saimiri infects T cells of primates and causes aggressive leukemias and ymphomas
• non-coding RNA expresses by HVS
• Binding of host miRNA to HSURs lead to their degradation
New therapies: Controlling microRNA expression
Controlling microRNA expression: different methods
Garzon et al, Nature Reviews Drug Discovery, 2010
A nice proof of principle
Cell, 2009
miR-26a expression is decreased in liver tumours
Kota et al. Cell, 2009
microRNA as a Cancer therapy: miR-26a
Expression of miR-26a in vivo
Kota et al. Cell, 2009
microRNA as a Cancer therapy: miR-26a
Kota et al. Cell, 2009Decrease in tumour mass
microRNA as a Cancer therapy: miR-26a
microRNA as a Cancer therapy: many examples
Kasinski and Slack, Nat. Rev. Cancer 2011
Slack’s group Nature, 2014
Cancers specific targeting: promising approach
low pH-induced transmembrane structure (pHLIP)
Mix therapy: Modulate microRNAs levels to sensitize tumoral cells to other conventional therapy
Molecular Cell, 2011
Role of microRNAs in drug resistance
Migliore et al, Trends in Molecular medicine, 2013
• Small non-coding RNAs (21 to 23 nucleotides long)
• First discovered in Caenorhabditis elegans
• Found in nearly all eukaryotes
• microRNA as new biomarkers
• Modulation of microRNA expression: new therapeutic strategy
• mRNAs from cancer cells as shorter 3’UTR
To summarize microRNAs: A new class of regulatory molecules
More than 10,000 microRNAs found in 103 species!
How microRNA are produced?
Where microRNAs come from?
Kim et al, Nature Reviews MCB, 2009
Two types of microRNAs
Kim et al, Nature Reviews MCB, 2009
1st processing step: the RNAseIII Drosha
Kim’s lab; Nguyen et al, Cell, 2015
• The microprecessor
• DGCR8 determine the precise cleavage site
2nd processing step: the RNAseIII Dicer
• TRBP and PACT are interacting with Dicer but are not essential for the activity
• Also important for the RNAi pathway
Kim et al, Nature Reviews MCB, 2009
How accurate processing of miRNAs work?
Park et al, Nature, 2011
Dicer recognizes the 5’ of pre-miRNA for efficient and accurate miRNA
production
Mutations in Dicer leads to cancer
Foulkes et al, Nature Rev. Cancer, 2014
Pleuropulmonary blastoma is the first cancer in which the responsible gene is
associated to microRNA pathway
And now 2nd processing step without Dicer!
Cell Research, 2010
• One example: miR-451
• Observed in mouse and zebrafish
Cheloufi et al, Nature, 2010
Cifuentes et al, Science, 2010
Science, 2005
• Highly conserved gene family
• Implicated in RNA silencing pathways
Argonautes: key players in the microRNA pathway
Nature Reviews MCB, 2008
Argonautes: Four conserved domains
Schirle and MacRae, Science 2012Elkayam et al, Cell 2012
Link between Argonaute and cancer
Yang et al, Molecular Cell, 2014
Argonaute is part of chain of reaction leading to tumorigenesis
Argonautes important for miRISC formation
Nature Reviews MCB, 2008
SlicingAGO
NAR, 2012
Asymmetry rule: guide which strand will be incorporated into the active complex
Schwarz et al and Khvorova et al, Cell 2003
Stability of the 5’ end dictateswhich strand will be associatedto Argonaute complex
• let-7 microRNA only appears after differentiation of embryonic stem cells
• the levels of pri- and pre-let-7 are identical in un- and differentiated ES cells
Kim (2004) and Hammond (2006) groups
pri-let-7
pre-let-7
let-7
Regulation of microRNA biogenesis: The let-7 case
• Determination of the protein associated to pre-let-7 lead to the discovery of Lin28 (RNA binding protein highly expressed in ES cells)
• Lin28 leads to the uridylation of pre-let-7 by Tut4
Regulation of microRNA biogenesis: The let-7 case
Gregory, Wulczin, Hammond and Kim groups
Heo et al. Cell, 2009
Regulation of microRNA biogenesis: The let-7 case
Molecular Cell, 2011
Regulation of microRNA biogenesis: MCPIP1 acts as a more general inhibitors
Winter et al. Nature Cell Biology, 2009
Regulation of microRNA biogenesis: SMAD proteins and hnRNPA1 facilitates cleavage
Regulation of the microRNA biogenesis: the beginning
Krol et al. Nature Reviews Genetics, 2010
• Subsets of microRNAs
• Sequence specificity
hnRNP A1 and KSRP
• Compete with the machinery
Controls of the turnover of microRNA pathway components emerge as a key player in the regulation
Bossé et al. Mol. Cell, 2013
• microRNAs stability
• Recycling of miRISC components
AGO
Dicer
AGO AAAAAAA
AGO
AGO
AGO
XRN DCS-1
Meziane et al. Sci. Rep, 2015
Modification of microRNAs: RNA editing
• Deamination from adenosine to inosine
• Alters base-pairing and stability
• Enzymes responsible for edition: ADAR1 and ADAR2
• pri-miR editing inhibits Drosha and Dicer cleavage and favors degradation by Tudor-SN
• Some pri-miRs editing favors processing by Drosha
• Can impact microRNA target specificity
Modification of microRNAs: Uridylation
• Terminal uridylyl transferases (TUTs)
• oligo-uridylation leads to pre-miRNA degradation (let-7 case)
• mono-uridylation favors pre-miRNA processing
• uridylation appears to favor turnover of degradation intermediates
Kim et al, EMBO J 2015
Post-translational modifications of microRNA pathway components: example Argonaute
Meister, Nature Rev. Genetics 2013
The microRNA pathway is regulated at many levels
Ha, Nature Rev. MCB 2014
How microRNA regulates gene expression?
MicroRNA binds by base complementarity to 3’UTRs
• Partial complementarity
• “seed” sequence defines microRNA family
• More microRNAs, more effect: cooperativity
• Abrogate protein synthesisOne microRNA may regulate up to 100 different genes!
Filipowicz Nature Reviews Genetics, 2008
Extended complementarity with the mRNA leads to endonucleolytic cleavage
Shin et al. Mol. Cell, 2010
MicroRNA serves as guide for Argonaute...
Tethering Argonaute to the 3’UTR is sufficient to induce
translational repression
Pillai et al. RNA, 2004
...but how it finds its mRNA target with such a low basepair complementarity?
Jannot et al. EMBO Rep., 2011rack-1 RNAi
ctl let-7 lin-41 daf-12
Rel
ativ
e as
soci
atio
nto
pol
ysom
es
0.2
0.6
1.0
P<0.005
RACK1 is a docking platform to recruit miRISC to the translation site
Discrepancy might be explained by the Argonautes
• 4 in humans and 2 in drosophila and C. elegans
• Binding partners
• fully complementary or bulged Dicer products
Iwasaki et al.Mol. Cell, 2009
Translational repression: Different models
Filipowicz Nature Reviews Genetics, 2008
Maybe more mRNA degradation then we thought...
...Well not settle yet!
Science, 2012
It most likely reflect the difference between different cellular states.
• Cytoplasmic granules
• Enriched in proteins involved in RNA catabolism and translation repression
• Many components interacts the miRISC complex
• Argonautes, GW182 and microRNA are found in these granules
The P bodies or GW-bodies
Filipowicz Nature Reviews Genetics, 2008
Fabian et al, NSMB, 2011
• GW182 recruits deadenylases
• Facilitates removal of the poly(A) tail by CCR4-NOT1
Chekulaeva et al, NSMB, 2011Braun et al, Mol. Cell, 2011
How GW182 contributes to microRNA gene regulation?
Release of the microRNA repression: rapid turnover
Cell, 2010
Extremely rapid turnover in neurons to respond quickly to stimuli
Modulators of microRNA function
AAAAAAAAgo
• Conditions specific
• Tissues specific
• Development specific
Interplay between microRNA complex and mRNA associated proteins: more and more examples
van Kouwenhove et al , Nat. Rev. Cancer 2011
Another function of microRNA: RNA binding proteins decoy
Beitzinger and Meister, Cell, 2010
A new class of RNA molecule called circular RNA competition for microRNA binding
Nature, 2013
Extremely abundant molecules in cells that contain complementary sites for microRNAs
To summarize
• Mainly produced by RNA polymerase II
• 1st maturation in the nucleus: microprocessor
• 2nd maturation in the cytoplasm: Dicer complex
• Active complex: miRISC Argonaute and microRNA
• In animals, binds non-coding regions (3’UTR)
• Abrogate protein synthesis
• What are the targets of microRNAs?
• How the microRNA pathway is controlled?
• How microRNAs regulate gene expression?
• Are microRNAs can travel from cell to cell and act in trans?
Questions to be answered
Questions/ comments [email protected]