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Processing
| Question | Answer |
|---|---|
| Ribosomal RNAs occur here with tRNAs | operons |
| The secondary structure of the tRNAs and rRNAs is recognized by RNA’ses and used for? | processing |
| 1)Primary processing occurs during transcription by | RNAse III, E, F and P (ribozyme). |
| 2) rRNAs associate with | ribosomal proteins |
| 3)RNAse D M5, 16 and 23 carry out | 5’ and 3’ mature end processing. |
| 4) Methylation, which protects the rRNA from RNAses | O2Me ribose, N6N6-dimethyl adenine. |
| Prokaryotic mRNA processing | little to none |
| Where does translation occur for prokaryotes? | nascent transcripts |
| Eukaryotic mRNA processing involves | capping, splicing, polyadenylation |
| Capping determines the site of | translation initiation |
| 7-methylG added co-transcriptionally via | 5',5'-triphosphate linkage |
| Cap can be differentially methylated where? | 2'-OH positions of first two nucleotides |
| cap-0 | no 2’-O-methyl, predominant in unicellular organisms |
| cap-1 | first nt, predominant in multicellular organisms |
| The CAP is involved in what? | Loading of ribosome onto mRNA during translation |
| Capping: 1: The 5' terminal triphosphate of the RNA is first removed by | RNA triphosphate |
| Capping: 2: GTP is added by | guanyltransferase |
| Capping:3: the 7 position of guanosine is | methylated |
| Capping:4: mRNA is methylated by | 2'-O-methyltransferase |
| In mammalian cells, primary transcripts have heterogeneous | 3' ends |
| All mRNAs have poly-A tails except | histone mRNA |
| Poly-Adenylation requires the presence of | AAUAAA element |
| The AAUAAA element is located | 10-35 nt upstream of site of poly-A tail |
| Poly-Adenylation also requires the presence of a U or | GU rich sequence about 50 nt downstream the cleavage site |
| C & PA requires a dynamic assembly of multiprotein complexes: | CPSF, CStF, CFI, CFII |
| Poly-A synthesis is catalyzed by a template independent polymerase known as | PAP |
| Why doesn't PAP need a template? | Telomere has a defined sequence |
| 3’ Cleavage and Polyadenylation: 1: CFI and CFII cleave RNA | 10-30 nuc 3' to signal |
| 2) PolyA polymerase adds poly A tail using | ATP |
| When does the CPSF disengage from recognition site? | Tail is 10-15 nucleotides long |
| 3) The length of the tail is controlled by | PABII |
| Multiple copies of PABII bind to the Poly A tail to | increase processivity |
| 4) Poly(A) binding protein (PAB) binds the tails and organizes them into | ribonucleoprotein particles. |
| Besides organizing tails/particles, what does PAB do? | involved in regulating translation initiation, protect mRNA |
| Unlike most prokaryotic RNA transcripts, many eukaryotic transcripts | contain introns |
| Class of intron is based on its | sequence properties |
| mRNA splicing is coupled with | transcription |
| mRNA splicing occurs sequentially in what direction? | 5' to 3' |
| The transesterification reactions require | no net input of energy |
| The transesterification reactions are catalyzed by | transphosphorylation reactions |
| However the splicing process does require net energy input for | conformational changes in the RNA and the spliceosome. |
| Spliceosome is a large complex (?) with more than 50 proteins | 50-60S |
| targets include nuclear pre-mRNA transcripts that | can not self splice |
| introns spliced by same lariat mechanism found for | GII introns |
| Eukaryotic nuclei contain numerous copies of small RNAs (60 - 300 nt long) known as | snRNA |
| there are five high abundant snRNAs involved in the splicing reaction: | U1, U2, U4, U5, and U6 |
| What are RNAs complementary to? | Consensus sequences in the intron |
| Spliceosome: 1) U1 SnRNA binds the | 5’ consensus sequence. |
| 2) U2 SnRNA binds lariat sequence after the lariat is bound by | the branch point binding protein (BBP) |
| The U2AF protein helps BBP select | the intron branch point. |
| 3) U5 SnRNAbinds to the | 3' splice junction |
| 4) A complex between U4 and U6 helps | bring everything together |
| 5)A series of rearrangements in the spliceosome generate the correct environment for | different transesterification reactions. |
| 6) Once together, U1 and U4 are destabilized and | spliceosome is reactivated |
Created by:
ScarlettRose
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