04 med shunu biol 2013
TRANSCRIPT
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Genu expression
DNS replication
Topic 4
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Role of RNA and protein synthesis in a
cell
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Actin
Nuclear myosin
Transcription
factor
Polymerase I
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Eukaryotic pre-mRNA processing
5' cap addition
5' capA 5' cap(also termed an RNA cap, an RNA 7-
methylguanosinecap, or an RNA m7G cap) is a modified
guanine nucleotide that has been added to the "front" or 5'
endof a eukaryotic messenger RNA shortly after the start of
transcription. Its presence is critical for recognition by the
ribosomeand protection from RNases.Splicing
Splicing is the process by which pre-mRNA is modified to
remove stretches of non-coding sequences called introns; the
stretches that remain include protein-coding sequences andare called exons. Splicing is usually performed by an RNA-
protein complex called the spliceosome, but some RNA
molecules are also capable of catalyzing their own splicing
(see ribozymes).
http://en.wikipedia.org/
http://en.wikipedia.org/wiki/5'_caphttp://en.wikipedia.org/wiki/7-methylguanosinehttp://en.wikipedia.org/wiki/7-methylguanosinehttp://en.wikipedia.org/wiki/5'_endhttp://en.wikipedia.org/wiki/5'_endhttp://en.wikipedia.org/wiki/Ribosomehttp://en.wikipedia.org/wiki/RNasehttp://en.wikipedia.org/wiki/Intronhttp://en.wikipedia.org/wiki/Exonhttp://en.wikipedia.org/wiki/Spliceosomehttp://en.wikipedia.org/wiki/Ribozymehttp://en.wikipedia.org/wiki/Ribozymehttp://en.wikipedia.org/wiki/Spliceosomehttp://en.wikipedia.org/wiki/Exonhttp://en.wikipedia.org/wiki/Intronhttp://en.wikipedia.org/wiki/RNasehttp://en.wikipedia.org/wiki/Ribosomehttp://en.wikipedia.org/wiki/5'_endhttp://en.wikipedia.org/wiki/5'_endhttp://en.wikipedia.org/wiki/7-methylguanosinehttp://en.wikipedia.org/wiki/7-methylguanosinehttp://en.wikipedia.org/wiki/7-methylguanosinehttp://en.wikipedia.org/wiki/5'_cap -
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Editing
mRNA can be edited, changing the nucleotide composition of thatmRNA. An example in humans is the apolipoprotein BmRNA,
which is edited in some tissues, but not others. The editing createsan early stop codon, which, upon translation, produces a shorter
protein.
Polyadenylation
Polyadenylation is the covalent linkage of a polyadenylyl moiety to a
messenger RNA molecule. In eukaryotic organisms all messengerRNA (mRNA) molecules are polyadenylated at the 3' end. The
poly(A) tailand the protein bound to it aid in protecting mRNAfrom degradation by exonucleases.
Polyadenylation occurs during and immediately after transcription of
DNA into RNA. After transcription has been terminated, themRNA chain is cleaved through the action of an endonucleasecomplex associated with RNA polymerase. After the mRNA has
been cleaved, around 250 adenosine residues are added to the free3' end at the cleavage site. This reaction is catalyzed by
polyadenylate polymerase.
http://en.wikipedia.org/
http://en.wikipedia.org/wiki/RNA_editinghttp://en.wikipedia.org/wiki/Apolipoprotein_Bhttp://en.wikipedia.org/wiki/Messenger_RNAhttp://en.wikipedia.org/wiki/Messenger_RNAhttp://en.wikipedia.org/wiki/Apolipoprotein_Bhttp://en.wikipedia.org/wiki/RNA_editing -
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RNA processing and splicing
http://www.youtube.com/watch?v=YjWuVrzvZYA
http://www.youtube.com/watch?v=FVuAwBGw_pQ
http://www.youtube.com/watch?v=YjWuVrzvZYAhttp://www.youtube.com/watch?v=FVuAwBGw_pQhttp://www.youtube.com/watch?v=FVuAwBGw_pQhttp://www.youtube.com/watch?v=YjWuVrzvZYA -
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Ribosomes in the cytoplasm and polysomes
attached to the endoplasmic reticulul (ER).
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http://www.youtube.com/watch?v=NJxobgkPEAo
Ribosomes
urnls "Nature " 9/27/2001
Ribosomas prvietoans virziens
http://www.youtube.com/watch?v=NJxobgkPEAohttp://www.youtube.com/watch?v=NJxobgkPEAohttp://www.youtube.com/watch?v=NJxobgkPEAo -
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4. stage:
5. stage:
6. stage:
7. stage:
How many phosphates arenecessary to produce asigle polypeptide (100amino acids)
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Proteins after translation
http://www.sumanasinc.com/webcontent/animations/content/lifecycleprotein.html
http://www.sumanasinc.com/webcontent/animations/content/lifecycleprotein.htmlhttp://www.sumanasinc.com/webcontent/animations/content/lifecycleprotein.html -
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Proteins of the secretory pathway are translocated into the endoplasmic reticulum(ER) lumen co-translationally through proteinaceous channels in the ERmembrane called translocons. b | In the extremely crowded, calcium-rich,oxidizing environment of the ER lumen, resident chaperones like BiP, calnexinand protein disulphide isomerase (PDI) serve to facilitate the proper folding of the
nascent protein by preventing its aggregation, monitoring the processing of thehighly branched glycans, and forming disulphide bonds to stabilize the folded
protein. c | Once correctly folded and modified, the protein will exit the ERthrough the formation of transport vesicles and move on through the secretory
pathway. d | If the ER quality-control system deems that the protein is malfoldedor unable to fold, it will be targeted for retrotranslocation to the cytosol and
degraded by the 26S proteasome. e | Changes in the ER environment shift thebalance from normal folding to improper folding (thicker arrow), leading to theaccumulation of unfolded proteins in the ER. This activates three ER-stresssensors IRE1, PKR-like ER kinase (PERK) and ATF6 which initiate theunfolded protein response. SRP, signal-recognition particle.
S
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Secretory proteins
signalpeptide
Ribosome
Ribosome
mRNA
mRNA
receptorpeptidase
translocator
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ER LUMENCYTOSOL
glucose
mannose
N-acetylglucosamine
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ER and turnover of ER resident proteins
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Golgi complex and N-linked glycosylation
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