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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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