Flashcards in 7-8: Transcription and Translation Deck (55):
What is the function of mRNA?
messenger RNA that codes fro proteins
What is rRNA?
ribosomal RNA, that forms the basic structure of the ribosome and catalyze protein synthesis
What is tRNA?
-acts as an adaptor between mRNA and amino acidss
What is snRNA?
-small nuclear RNA
- splice pre-RNA and other nuclear function
What is snoRNA?
-small nucleolar RNA
- process and chemically modify rRNAs
What are miRNA?
-regulate gene expression by blocking translationof specific mRNA and produce their degradation
What are siRNA?
-small interfering RNA
- control gene expression by directing degradation of selective mRNA and establishing compact chromatin structures
Why can RNA poly have a lower fidelity than that of DNA poly?
-the mistakes that are made are not transmitted to the progeny, therefore mistakes are more allowed
What subunits make up the bacterial RNA polym?
- alpha2, beta, beta prime, sigma
The mRNA strand that is synthesized is most similar to what?
-complementary to the template strand
- identical to the coding strand
What are two common motifs in bacteria that signal for transcription initiation?
- TTGACA at -35
- TATAAT box at -10 from the initiation site
What does RNA polym encounter that helps initiate the termination of transcription?
- GC,AT rich region contributes to the formation of a hairpin which causes a pause in RNA Polym.
- the hairpin adds new tension to the RNA polym and RNA strand, causing it to destabilize due to weak attachment bc of increased AU interactions
- mRNA leaves and the transcription bubble closes
Eukaryotes require more than one RNA polymerase to perform transcription. What are these and which is the most important?
1. RNA Polymerase I, II, III
2. polym II: all protein coding genes, and the other RNA types mentioned
What is the main regulator that controls the RNA poly II activity?
- the regulator is phosphorylation of Ser residues located on the carboxyl-terminal domain
What unit contains the TBP, TATA-box binding protein?
1. TFII D recognizes the TATA binding region
What factors combine to form the transcription initiation complex?
TFIIB, TFIIF, RNA poly II, TFIIE, and TFIIH
What process occurs that causes the end of initiation and begins the elongation process?
- TFIIH phosphorylates the carboxyl-terminal domain, and forces the polymerase to leave the promoter
Eukaryotic polymerase TFIID TBP subunit does what function?
- recognize the TATA box
Eukaryotic polymerase TFIID TAF subunit has what function?
- regulate DNA binding by TBP, and recognize other DNA sequence near transcription start point
Eukaryotic polymerase TFIIB has what function?
- recognize BRE element in promoters. accurately positions RNA polymerase at the start site of transcription
Eukaryotic polymerase TFIIF has what function?
- stabilize RNA polym interaction with TBP and TFIIB
Eukaryotic polymerase TFIIE has what function?
- attract and regulate TFIIH
Eukaryotic polymerase TFIIH has what function?
- unwinds DNA at start point, releases RNA polymerase from the promoter
What are recruited to increase the accessibility of DNA to specific enzymes?
1. chromatin modifying enzymes
- chromatin remodeling complex
-histone modifying enzymes
What RNA processing occurs before the mRNA is released from the nucleus into the cytoplasm in eukaryotes?
1. RNA capping to the 5' end
2. RNA splicing, which removes non-coding sequences
3. Poly A tail to the 3' end
What is the 5' cap formed by?
7-methylguanosine that is bound to the 5'end via a triphosphate bridge
What are the functions of the 5' cap that is added to mRNA before it leaves the nucleus?
1. marks the translation start site
2. protects mRNA from phosphatases and nucleases
3. binds to a cap binding complex to facilitate RNA processing and export.
What two proteins are attached to the newly formed RNA as it is formed?
1.cleavage stimulation factor (CstF)
2. Cleavage and polyadenylation specificity factor (CPSF)
Where does the cleavage stimulation factor (CstF) bind to the new RNA strand?
to the GU rich region
Where does cleavage and polyadenylation factor bind on the new RNA strand? (CPSF)
binds at the AAUAAA 3' end
What are the general process that take place to get eukaryotes DNA to protein?
1. transcription in nucleus to form primary RNA transcript
2. RNA modification (poly A tail, 5' cap, splicing)
3. nuclear exportation
4. translation in cytoplasm to form proteins
What are the general process that take place to get prokaryotes DNA to protein?
1. transcription occurs in the cytoplasm
2. mRNA is directly translated into protein
What is the function of a mediator?
allows the activator proteins to communicate with RNA Pol II and general transcription factors
What is the primary reason chromatin modifying enzymes are used for?
allow more access to chromatin remodling complex
and histone modifying enzymes
Where does translation occur?
What is the function of tRNA?
1. adaptor that binds to specific codons and brings an amino acid to incorporate into the polypeptide chain
What are two important regions on the tRNA?
2. acceptor stem
What is the anticodon region on tRNA used for?
Allows for complementary binding on an mRNA molecule
What is the acceptor stem of tRNA used for?
This is a CCA region that binds to the amino acids, that corresponds with the proper anticodon sequence
What is the best explanation as to why a large majority of codons for a single amino acid differ in the 3rd binding region?
How are amino acids attached to the correct tRNA?
use of aminoacyl-tRNA synthetases; which use covalent bonds to bind the AA to the 3'terminal ribose residue
How does hydrolytic editing work, and what is it for?
1. an editing region that uses the size of the attached amino acid to verify it correct. if not it is cleaved and removed.
What are the prokaryote and eukaryote ribosomes?
1. prokaryote: 70S
2. eukaryote: 80S
What is thr primary function of the small s.u.?
form a framework where tRNA can accurately match with there codon
What is the large s.u. function?
catalyze the formation of peptide bond linking the AA together on the polypeptide chain
What are the 4 steps of translation?
1. tRNA binds
2. peptide bond forms
3. large subunit translocates
4. small subunit translocates
How does the small subunit bind to the mRNA?
recognize the 5'cap and the eIF4E and eIF4G
Which elongation factors aid eukaryotes to improve the efficiency of operation?
EF1 and EF2
Which elongation factors aid bacteria with elongation?
EF-Tu and EF-G
What is a way that antibiotics are effective against bacterial infections?
they bind to ribosomes and interfere with protein synthesis
What effect does tetracycline have on bacteria?
blocks aminoacyl-tRNA binding to the A site
What does streptomycin do to bacteria?
prevents the transition from translation initiation to elongation.
What makes erythromycin an effective antibiotic against bacterial microbes?
binds in the exit channel of the ribosome and inhibits elongation of the peptide chain
Why is puromycin effective against bacteria and eukaryotes?
releases the nascent peptide by adding to the growing chain end