RNa metabolism II 26 done Flashcards
(33 cards)
What does RNA polymerase I synthesis?
pre-ribsomal RNA (prescurser for 28S, 18S, 5.8S rRNAS)
WHat does RNA polymerse II?
Primary enzyme that creates mRNA. Very fast and is targeted by mushroom toxin (inhibits it)
What is RNA polymerase III?
Mates tRNAs and small RNA products
WHat is RNA polymerase IV?
IN plants that synthesis by small interfering RNAs
What cell has more than one RNA polymerase?
mitochondria, different DNA
WHat does +1 mean in a promoter seuqnece?
1st. nucleotide subscribed at 3’ end, It is the initation sequence
WHat are transciption factors?
manage transcirption. any protein involed in transcription
Describe the common features of a typical RNA polymerase’s promotor
at the 3’ end, theire is the initation sequence at +1, the TATA box at -30, and farther upstream, the points of regulation
What is TBP?
It is a transcirtioion factor protein (TATA binding protein) that binds to the TATA box of the RNA poly II promoor
WHen and where does TFIIB bind?
It binds on the opposite side where the TBP bound on the DNA. It binds after TBP
What is the of TFIIA?
It stabilizes TFIIB-TBP. doesn’t always
s t
What is TFIIF?
trancirption factor that brings POl-II to promotor. it associates with TFIIB
WHich transcription factors are involved in the final assembly of the closed complex?
TFIIE and TFIIH
Why is TFIIH important?
It is a helicase that creates the open complex, starting initation. It is also a kinase, because it contains the amino acid sequence YSPTSPS in carboxyl-terminal domain (CTD), which can be phosphorylated, activating it to begin transcription. If not phosphoralayted, no trancription
When does elongation occur?
After the TFIIH is phosphorylated on CTD, nucleotides (60-70) can be synthesised. After, TFIIE and TFIIH are released, elongation phase begins
How do intercalating agents, like Actinomycin (Act D) and Acridine orange inhibit transcription?
Inserts itself into DNA to disrupt it. It has an aromatic group that can enter where base pairs are crosslinked, triggering a bend or kink. This stops RNA polymerase from progressing. Used as antibiotics but not specific so can damage cellls.
What is Rifampicin?
drug that blocks RNA synthesis by stoping RNA polymerase from binding to DNA. It is more specific - stops binding in bacteria. a-amanitin, death cap mushroom
what is capping? what is the benefit?
adding 7-methylguanosine to the 5’ terminal residue in the syn direction. This protects the mRNA from degredation by 5’ exconuclease because the bases are usualy in anti positions. With capping, the 2’ carbons of the first 2 nucleotides may be methylated (doesn’t cause mutation because these are sugars, not the bases). there may also be a 5’ triphosphate bind between the first nucleotide and ther capped one
WHich is more complexed eukarote or pro temindation (transcription?
eukaryo. DOesn’t use rho
WHich enzymes facilitate the capping of an mRNA?
Phosphohydrolase, which removes a phosphate, guanylytransferase, which addes GMP, and guanine-7-methyl transferase, which methylates guanine
WHere are capping enzymes bound to? WHen do they add?
The CTD of RNA pol II. WHen bound, it is called the cap-synthesizing complex. They begin capping after 20-30 enzymes are added. TThe CSC will then release once the cap is done being added.
WHat is splicing?
removal of introns from the primary transcript. must be done before protein synthesis
WHich introns are self-splicing?
group 1 and 2. They do not need a protein. They are found in mRNA, tRNa, and rRNA genes, which are found in nuclear, mitochondrial, and chloroplast genomes
WHich group of introns is the most common?
spliceosomal introns. Are spliced by spliceosome (large RNA proteinn complex). are frequent in protein-coding regions of eukaryotic genomes
