RNA Interference (RNai) Flashcards
What is RNA interference (RNai)?
A cellular process used in animals, plants and single-celled fungi to protect cells against viruses and transposable elements.
What triggers the RNA interference pathway?
The production of long double-stranded RNA (dsRNA) transiently during the life cycles of viruses and active transposable elements.
What are the characteristics of short interfering RNA (siRNA)?
siRNA is approximately 21 base pairs long and produced by asymmetric cutting, resulting in two nucleotide overhangs at their 3’ ends.
What role does Dicer play in RNAi?
Dicer is a cytoplasmic endoribonuclease that cuts long dsRNA into short double-stranded RNA pieces, known as short interfering RNA (siRNA)
What happens to siRNA duplexes in the RNAi pathway?
They are bound by complexes containing an argonaute-type endoribonuclease (Ago) and other proteins.
How are RNA strands processed after binding to the argonaute complex?
RNA strands are degraded by the argonaute, leaving a single-stranded RNA bound to the argonaute complex.
What happens when the argonaute complex is activated?
The siRNA acts as a guide RNA, directing the argoanaute complex to its target RNA by base-pairing with complementary RNA sequences in the cells.
What is the function of the RNA-induced silencing complex (RISC)?
After the siRNA guide binds to a complementary long single-stranded RNA, the argonaute enzyme cleaves the RNA, leading to its degradation and inactivation of viral and transposon RNA.
What is the function of the RNA-Induced Transcriptional Silencing (RITS) complex?
The RITS complex binds to complementary RNA transcripts during transcription, attracting proteins like HMT and DNMT to modify histones, leading to heterochromatin formation and spreading, and sometimes DNA methylation resulting in long-term gene expression silencing.
What is the overall function of the RNA interference (RNAi)?
RNAi defends against viruses and transposon by degrading their RNA or silencing their transcription through siRNA and complexes like RISC and RITS.
What are the end products of Dicer’s action on long dsRNA?
Short interfering RNA (siRNA)
What proteins are found in the complexes that bind siRNA duplexes?
Complexes contain an argonaute-type endoribonuclease (Ago) and other associated proteins.
How does the siRNA guide RNA interact with the target RNA?
The siRNA guide RNA base-pairs with complementary RNA sequences in the cell, directing the argonaute complex to the target RNA.
Describe the degradation process of RNA strands in the RNAi pathway.
The argonaute enzyme degraded one strand of the RNA duplex, leaving a single-stranded RNA bound to the argonaute complex.
How does the RITS complex affect chromatin structure?
The RITS complex attracts histone methyltransferases (HMT) and DNA methyltransferases (DNMT), which modify histones and lead to heterochromatin formation and spreading.
