CRAZY ABOUT BIOMECIDINE Having a look into frog oocytes
TRANSLATIONAL CONTROL OF mRNAs BY CYTOPLASMIC POLYADENYLATION
DURING MEIOSIS
Slide 2
Gene expression Gene regulation Translational control of mRNAs
CPEBs & cytoplasmic polyadenylation Meiosis and translational
control of mRNAs mediated by CPEBs CPEBs beyond meiosis
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GENE EXPRESSION Genetic information Effectors Cell signaling
Cell adhesion Enzymes Define the structure Transport
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GENE EXPRESSION Genetic information Effectors Cell signaling
Cell adhesion Enzymes Define the structure Transport Key steps in
gene expression RNA transcription: from DNA to RNA RNA processing:
from RNA to mRNA mRNA transport: from the nucleus to the cytoplasm
Protein translation: from mRNA to protein
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GENE EXPRESSION Genetic information Effectors Cell signaling
Cell adhesion Enzymes Define the structure Transport RNA processing
DNA Pre-mRNA mRNA
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GENE EXPRESSION Genetic information Effectors Cell signaling
Cell adhesion Enzymes Define the structure Transport mRNA features
CDS 5UTR3UTR 5 cap AAAAAAAAAA AUG UGA
Slide 7
GENE EXPRESSION Genetic information Effectors Cell signaling
Cell adhesion Enzymes Define the structure Transport Protein
translation
Slide 8
TRANSLATIONAL CONTROL OF mRNAs BY CYTOPLASMIC POLYADENYLATION
DURING MEIOSIS Gene expression Gene regulation Translational
control of mRNAs CPEBs & cytoplasmic polyadenylation Meiosis
and translational control of mRNAs mediated by CPEBs CPEBs beyond
meiosis
Slide 9
GENE REGULATION EVERY CELL IN A GIVEN ORGANISM CONTAINS THE
SAME GENETIC INFORMATION DIFFERENCES IN GENE EXPRESSION
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GENE REGULATION Every step in gene expression is regulated
TRANSCRIPTION Accessibility of DNA Transcriptional regulation
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GENE REGULATION Every step in gene expression is regulated RNA
PROCESSING Alternative splicing Alternative 3UTR formation:
different 3UTR AAA CDS 5UTR 3UTR 5 cap AAA AUG CDS AUG
TRANSCRIPTION Accessibility of DNA Transcriptional regulation
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GENE REGULATION Every step in gene expression is regulated RNA
PROCESSING Alternative splicing Alternative 3UTR formation:
different 3UTR PROTEIN TRANSLATION Global vs. mRNA specific
regulation Translational repression precluding ribosome recruitment
or progression through the mRNA TRANSCRIPTION Accessibility of DNA
Transcriptional regulation
Slide 13
TRANSLATIONAL CONTROL OF mRNAs BY CYTOPLASMIC POLYADENYLATION
DURING MEIOSIS Gene expression Gene regulation Translational
control of mRNAs CPEBs & cytoplasmic polyadenylation Meiosis
and translational control of mRNAs mediated by CPEBs CPEBs beyond
meiosis
Slide 14
TRANSLATIONAL CONTROL OF mRNAs WHY mRNAs should be stored in
the cytoplasm instead of being immediately translated? AAAAAA
nucleus cytoplasm AAAAAA A Once transcribed, mRNAs can have
different fates.
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TRANSLATIONAL CONTROL OF mRNAs WHY mRNAs should be stored in
the cytoplasm instead of being immediately translated? Rapid
response Absolutely required in situations with absence of
transcription To solve long distances (axons can extend up to 1
meter!)
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TRANSLATIONAL CONTROL OF mRNAs mRNA translation can be divided
into 3 phases: initiation, elongation and termination All mRNAs
exit the nucleus with a long poly(A) tail and should be efficiently
translated INITIATION is the phase more tightly controlled
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TRANSLATIONAL CONTROL OF mRNAs HOW TO CONTROL TRANSLATION AT
INITITATION? sequestering initiation factors blocking the 5 cap
shortening the poly(A) tail AAAAAAAAAAAAA 4G 4E 4E- BP Sequester
initiation factors
Slide 18
TRANSLATIONAL CONTROL OF mRNAs HOW TO CONTROL TRANSLATION AT
INITITATION? sequestering initiation factors blocking the 5 cap
shortening the poly(A) tail AAAAAAAAAAAAA 4G 4E AAAAAAAAAAAAA 4E
Block the 5 cap no recruitment of the ribosome
Slide 19
TRANSLATIONAL CONTROL OF mRNAs HOW TO CONTROL TRANSLATION AT
INITITATION? sequestering initiation factors blocking the 5 cap
shortening the poly(A) tail AAAAAAAAAAAAA 4G 4E A Shorten the
poly(A) tail no close loop
Slide 20
TRANSLATIONAL CONTROL OF mRNAs HOW TO CONTROL TRANSLATION AT
INITITATION? sequestering initiation factors blocking the 5 cap
shortening the poly(A) tail AAAAAAAAAAAAA 4G 4E TRANSLATIONAL
REPRESSION doesnt last forever!!! Activation of mRNA translation
Cell stimuli releasing initiation factors allowing the 5 cap to
interact with initiation factors elongating the poly(A) tail How to
activate translation?
Slide 21
TRANSLATIONAL CONTROL OF mRNAs BY CYTOPLASMIC POLYADENYLATION
DURING MEIOSIS Gene expression Gene regulation Translational
control of mRNAs CPEBs & cytoplasmic polyadenylation Meiosis
and translational control of mRNAs mediated by CPEBs CPEBs beyond
meiosis
Slide 22
CPEBs and CYTOPLASMIC POLYADENYLATION A 4E NO TRANSLATION
Polyadenylation can happen in the cytoplasm!!!! AAAAAAAAAAAAA 4G 4E
TRANSLATION
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CPEBs and CYTOPLASMIC POLYADENYLATION CPEBs play an essential
role RNA binding proteins Bind to specific sequences in the 3UTR of
target mRNAs Have a dual function!!!! CPEB in repressionCPEB in
activation CPEB recruits other proteins that shorten the poly(A)
tail and block the cap CPEB recruits other proteins that elongate
the poly(A) tail WHAT MAKES THE DIFFERENCE???? stimulus Kinase
activation
Slide 24
TRANSLATIONAL CONTROL OF mRNAs BY CYTOPLASMIC POLYADENYLATION
DURING MEIOSIS Gene expression Gene regulation Translational
control of mRNAs CPEBs & cytoplasmic polyadenylation Meiosis
and translational control of mRNAs mediated by CPEBs CPEBs beyond
meiosis
Slide 25
MEIOSIS and CPEBs
Slide 26
Model system: Xenopus laevis oocytes Oocytes arrested at the
prophase of meiosis I (progesterone makes them progress to
metaphase of meiosis II) Eggs arrested at the metaphase of meiosis
II (fertilization makes them finish meiosis and start embryonic
divisions) Oocytes Eggs progesterone fertilization
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MEIOSIS and CPEBs Model system: Xenopus laevis oocytes Prophase
I arrested oocytes grow until they are fully competent for
development: 6 growth stages >1.2mm! (human: 0.12mm)
Accumulation of molecular reserves Like maternal mRNAs! MEIOSIS AND
FIRST EMBRYIONIC DIVISIONS HAPPEN IN THE ABSENCE OF TRANSCRIPTION!
PROTEIN EXPRESSION DUE TO TRANSLATIONAL ACTIVATION OF mRNAs!
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MEIOSIS and CPEBs sVI. Oocytes progesterone Requires activation
of translation of stored mRNAs Model system: Xenopus laevis oocytes
Meiotic progression requires protein translation!!!!
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MEIOSIS and CPEBs Model system: Xenopus laevis oocytes Meiotic
progression requires protein translation!!!! Stage VI oocytes store
A LOT of maternal mRNAs repressed by CPEB1 + progesterone MEIOSIS
RESUMPTION CPEB1 is phosphorylated Activation of translation of
mRNAs
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MEIOSIS and CPEBs CPEB1 is not the only one! CPEB4 takes the
job in late meiotic phases. Oocytes arrested prog. CPEB1CPEB4 CPEB1
degraded CPEB4 synthetized repression activation
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MEIOSIS and CPEBs CPEB1 is not the only one! CPEB4 takes the
job in late meiotic phases. They both recognize the same elements
in the 3UTR of target mRNAs. CPEB1 degraded CPEB4 synthetized
progesterone Aurora A kinase activity CPEB1 repression activation
Oocytes arrested
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CURIOSITY THE POWER OF THE CYTOPLASM! Early development happens
in the absence of transcription Everything you need for early
development is contained in the egg cytoplasm
Slide 33
TRANSLATIONAL CONTROL OF mRNAs BY CYTOPLASMIC POLYADENYLATION
DURING MEIOSIS Gene expression Gene regulation Translational
control of mRNAs CPEBs & cytoplasmic polyadenylation Meiosis
and translational control of mRNAs mediated by CPEBs CPEBs beyond
meiosis
Slide 34
CPEBs BEYOND MEIOSIS CPEBs are involved in local translation in
dendrites CPEBs are required for long term memory CPEBs are
involved in cell proliferation, angiogenesis CPEB4 is involved in
pancreatic adenocarcinoma