PHILLIPS CH13

Question 1

Argonaute

Answer 1

bind small RNAs, functional molecule that allows small RNA to interact with mRNA
promote cleavage and mRNA degradation, translational repression and mRNA decay, chromatin modification at specific genomic loci

Question 2

microRNA (miRNA)

Answer 2

derived from primary transcripts, repress translation and promote mRNA decay

Question 3

small interfering RNA (siRNA)

Answer 3

derived from long dsRNAs, primarily targets RNA for degradation and and acts as a cellular defense mechanism

Question 4

RNAi-induced silencing complex (RISC)

Answer 4

RNA (miRNA or siRNA) and argonaute protein

Question 5

RNA interference (RNAi)

Answer 5

injecting dsRNA induces RNA silencing - suppresses gene function

C. elegans experiment

Question 6

genome-encoded regulatory RNAs

Answer 6

1) antisense: on DNA strand antisense to target
2) trans-encoded: completely separate DNA region
3) cis-encoded: part of the target (riboswitches)

Question 7

piwi-interacting RNAs (piRNAs)

Answer 7

interact with Piwi proteins, derived from repetitive regions of the genome and down regulate transcription

Question 8

Drosha and Dicer

Answer 8

proteins involved in miRNA and siRNA processing
recognize and cleave dsRNA with RNase III activity

Drosha: accessory protein DGCR8
Dicer: secures cut RNA with PAZ domain

Question 9

miRNA biogenesis

Answer 9

in nucleus, Drosha/DGCR8 cleaves bottom of stem loop > pre-miRNA, exported to cytoplasm
Dicer binds cut end to PAZ domain and cleaves top to miR duplex

Question 10

siRNA biogenesis

Answer 10

in cytoplasm, dicer chops up long dsRNAs sequentially every 20-25 bps, forming siR duplex

Question 11

miRISC

Answer 11

imperfect complementarity prevents cleavage so miRISC stays on the RNA. prevents translation, recruit capping and other degredation factors

Question 12

siRISC

Answer 12

Argonaute cleaves the target RNA, enters the nucleus and suppresses transcription through DNA and H3K9 methylation, silencing the gene