Molecular Biology Chapter 19: Noncoding RNA

What is coding RNA?

mRNA that encodes protein to act as various components including enzymes, cell structures, and signal transductors

Coding RNA includes:

mRNA, viral genomes

What is noncoding RNA (ncRNA)?

act as cellular regulators without encoding proteins

Noncoding RNA includes:

tRNA, rRNA, ribozymes, scaffolding, regulatory, defense, long noncoding

Ribozyme contain: (last one processes tRNAs; can function w/o protein in vitro).

catalytic RNA, self-splicing introns, spliceosomes, RNase P

50-450, most act via antisense mechanism, bind mRNA and block translation, and modulate expression levels (don't completely turn on/off)

Prokaryotic Small Regulatory RNAs (sRNAs)

RyhB + Hfq + RNase E System is an example of

sRNAs

RyhB responds to iron shortage, Hfq protein stabilizes sRNA and recruits RNase E, blocks ribosome-binding site (which prevents translation), and RNase E degrades mRNA (not sRNA)

True

Anti-bfr RNA pairs with bfr mRNA, forms dsRNA (prevents translation), whjen iron is plentiful, only bfr mRNA is produced.

Bacterioferritin Regulation

CsrB and CsrC act as "sponges" sequestering CsrA, and CsrA binding can stabilize or destabilize mRNA depending on target. What are the CsrA Translation Control Components?

CsrA protein, CsrB and CsrC RNAs

tRNA fragments (tRFs), Long Noncoding RNAs (IncRNAs), Enhancer RNA (eRNA), and Circular RNA (circRNA) are examples of?

Eukaryotic Noncoding RNAs

tRNA fragments (tRFs):

tRF-1: From 3' end processing (RNase Z)

tRF-3: From 3' end of mature tRNA (Dicer)

tRF-5: From 5' end of mature tRNA (Dicer)

tiRNAs: Stress induced, cut by Angiogenin

True

What does IncRNA stand for?

Long Noncoding RNAs

Are IncRNAs more common in eukaryotes or prokaryotes?

Eukaryotes

What are the transcription levels of IncRNAs?

Low transcription levels

Do IncRNAs have a 5' cap and polyA tail?

Yes, but they are not translated

What is one function of IncRNAs?

Regulating gene expression

How do IncRNAs interact with miRNAs?

They can block miRNA interactions by acting as sponges

What role do IncRNAs play in splicing?

They sequester splicing proteins

What is one structural role of IncRNAs?

They hold enhancer complexes together

How do IncRNAs contribute to chromatin structure?

They act as scaffolds for chromatin structure

What is the role of IncRNAs in X-inactivation?

Xist is an IncRNA involved in X-inactivation

Enhancer RNA (eRNA)

Type of noncoding RNA transcribed from enhancer sequences that holds enhancer and target gene together in DNA loop and works with mewdiator complex and RNA polymerase II

Circular RNA (circRNA)

Molecules found in eukaryotic cells. Some contain binding sites for miRNAs. Generated by "back splicing" and are resistant to degradation (no free ends) and possible function as miRNA sponge.