Small non-coding RNAs Flashcards
What is considered as small non-coding RNAs?
smaller than 200bp
how long are micro RNA miRNAs?
21-24 nt
How do miRNAs regulate gene expression?
through base pairings with mRNAs
They down-regulate miRNA synthesis
Where do miRNAs bind?
to 3’ UTRof mRNA target in mature mRNA: the 3’ UTR are untranslated regions usually containing regulatory information
How is miRNA synthesised?
made from a long precursor RNA, transcribe and present in the nucleus
miRNA synthesis
The RNA forms a secondary structure which are recognised by enzymes that cut them to form an intermediate. Those intermediates are transported to the cytoplasm where other enzymes recognise and further cut it. Argonaute proteins recognise the double-strand RNA structure and load one single strand RNA on the target mRNA
How do miRNAs help regulate the transitions between developmental stages?
By blocking/removing mRNAs that define an earlier developmental stage
siRNAs
similar size to miRNAs
used as a cell defense mechanism against pathogens
How can siRNAs be used?
- They can follow the same pathway used for miRNAs using Argonaute proteins
- The single-strand RNA recognises nascent RNA produced by RNA polymerase: activates a pathway whereby there is heterochromatin formation on the gene undergoing transcription
What is used by the presence of viral remnants in our genome?
Regulates the expression of protein-coding genes
How were viral remnants integrated in the human genome?
Through retro-transcription
piwi-interacting RNAs piRNAs
made selectively in the germline to protect them from transposable elements
What is the most abundant small noncoding RNA?
piRNAs
What do piRNAs do?
Silence TE genes and degrades TE RNAS. They are a system to distinguish self RNAs from foreign RNAs
