biology

MicA RNA

MicA RNA is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand MicA RNA rather than just read about it. In short: The MicA RNA (also known as SraD) is a small non-coding RNA that was discovered in E. coli during a large scale screen. Expression of SraD is highly abundant in stationary phase, but low levels could be detected in exponentially growing cells as well.

Key takeaways

MicA RNA belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect MicA RNA to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of MicA RNA from memory before moving on to harder problems.

Reference excerpt

The MicA RNA (also known as SraD) is a small non-coding RNA that was discovered in E. coli during a large scale screen. Expression of SraD is highly abundant in stationary phase, but low levels could be detected in exponentially growing cells as well.

Function This RNA binds the Hfq protein and regulates levels of gene expression by an antisense mechanism. It is known to target the OmpA gene in E. coli and occludes the ribosome binding site. Under conditions of envelope stress, micA transcription is induced. MicA, RybB RNA and MicL RNA transcription is under the control of the sigma factor sigma(E). In E.coli, SraD also interacts in cis and trans with the mRNA species, luxS, ompA and phoP, respectively. This observation describes MicA to be the first known sRNA to carry out antisense regulation in both structural configurations. MicA is known to interact with the mRNA encoding the quorum sensing synthase homolog, LuxS in E.coli and both RNAs are processed by the double stranded RNA endonuclease, RNase III. Based on its conservation, this is presumably the case in close relatives and may serve as a long elusive link between envelope stress and quorum sensing. The PhoPQ two-component system is repressed by MicA. The RNA presumably pairs with the ribosomal binding site of phoP mRNA, thereby inhibiting translation. This links micA to cellular processes such as Mg(2+) transport, virulence, LPS modifications and resistance to antimicrobial peptides. In S. typhimurium MicA has been shown to be involved in biofilm formation. It is observed that the luxS mutant biofilm formation process is found to be dependent on MicA in cases where the gene's coding region is deleted, however, it is still not known to what extent MicA is involved in this mechanism. Site directed mutagenesis has been used to construct mutated forms of MicA forms in order to investigate the RNA determinants important to its stability and function. Each 'domain' investigated ( 5′linear domain, the structured region with two stem-loops, the A/U-rich sequence and the 3′ poly(U) tail) was altered without affecting the overall secondary structure of MicA however, each 'domain' was found to have a different impact on stability and the ability of MicA to regulate its multiple targets.

References

Further reading Karavolos MH, Bulmer DM, Spencer H, Rampioni G, Schmalen I, Baker S, et al. (March 2011). "Salmonella Typhi sense host neuroendocrine stress hormones and release the toxin haemolysin E". EMBO Reports. 12 (3): 252–8. doi:10.1038/embor.2011.4. PMC 3059909. PMID 21331094. Moores A, Chipper-Keating S, Sun L, McVicker G, Wales L, Gashi K, Blomfield IC (January 2014). "RfaH suppresses small RNA MicA inhibition of fimB expression in Escherichia coli K-12". Journal of Bacteriology. 196 (1): 148–56. doi:10.1128/JB.00912-13. PMC 3911127. PMID 24163336.

External links

Page for SraD RNA at Rfam

Illustrations

Worked examples

Example 1 — a first encounter with MicA RNA

Start with the simplest possible case. Write down what MicA RNA claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to MicA RNA before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about MicA RNA ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of MicA RNA

In research: MicA RNA appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses MicA RNA in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: MicA RNA is common in secondary-school and first-year university syllabi. It links to neighbouring topics Molecular and cellular biology stubs, Non-coding RNA, so understanding it makes those chapters shorter.
In everyday life: Look for MicA RNA outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study MicA RNA in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what MicA RNA means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain MicA RNA out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is MicA RNA in simple terms?

Why does MicA RNA matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study MicA RNA?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on MicA RNA.