biology

MIR34A

MIR34A 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 MIR34A rather than just read about it. In short: MicroRNA 34a (miR-34a) is a microRNA that in humans is encoded by the MIR34A gene. Function microRNAs (miRNAs) are short (20–24 nt) non-coding RNAs that are involved in post-transcriptional regulation of gene expression in multicellular organisms by affecting both the stability and translation of mRNAs. miRNAs are transcribed by RNA polymerase II as part of capped and polyadenylated primary transcripts (pri-miRNAs)…

Key takeaways

MIR34A belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect MIR34A to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of MIR34A from memory before moving on to harder problems.

Reference excerpt

MicroRNA 34a (miR-34a) is a microRNA that in humans is encoded by the MIR34A gene.

Function microRNAs (miRNAs) are short (20–24 nt) non-coding RNAs that are involved in post-transcriptional regulation of gene expression in multicellular organisms by affecting both the stability and translation of mRNAs. miRNAs are transcribed by RNA polymerase II as part of capped and polyadenylated primary transcripts (pri-miRNAs) that can be either protein-coding or non-coding. The primary transcript is cleaved by the Drosha ribonuclease III enzyme to produce an approximately 70-nt stem-loop precursor miRNA (pre-miRNA), which is further cleaved by the cytoplasmic Dicer ribonuclease to generate the mature miRNA and antisense miRNA star (miRNA*) products. The mature miRNA is incorporated into a RNA-induced silencing complex (RISC), which recognizes target mRNAs through imperfect base pairing with the miRNA and most commonly results in translational inhibition or destabilization of the target mRNA. The RefSeq represents the predicted microRNA stem-loop.

Repair of DNA damage Expression of miR-34A is markedly up-regulated in hematopoietic stem cells (HSCs) from mice subjected to ionizing radiation. HSCs that are deficient in miR-34A have decreased expression of genes involved in the DNA repair processes of homologous recombination and non-homologous end joining. These and other findings demonstrate that miR-34A contributes to the survival of HSCs after irradiation.

Clinical relevance miR-34a suppresses the gene expression of NAMPT, which encodes nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the nicotinamide adenine dinucleotide (NAD) salvage pathway, resulting in reduced levels of NAD. miR-34a suppression of NAMPT gene expression also reduces levels of sirtuin 1. Aging and obesity increase levels of miR-34a. The pro-inflammatory transcription factor NF-κB (increasingly expressed with obesity and aging) increases miR-34a expression by binding to its promoter region. Inhibition of miR-34a in diet-induced obese mice restored levels of NAMPT and NAD, reducing inflammation and improving glucose tolerance. miR-34a represses the translation of sirtuin 1 (SIRT1) in liver by binding to the 3′-UTR region of SIRT1 messenger RNA, contributing to metabolic syndrome. Downregulation of SIRT1 by miR-34a promotes cellular senescence and inflammation in vascular smooth muscle cells of old mice, similar to reduced SIRT1 in vascular smooth muscle cells in humans. Impaired endothelial-dependent vasorelaxation caused by miR-34a can be ameliorated by SIRT1 overexpression.

References

Illustrations

Worked examples

Example 1 — a first encounter with MIR34A

Start with the simplest possible case. Write down what MIR34A 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 MIR34A 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 MIR34A 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 MIR34A

In research: MIR34A 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 MIR34A 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: MIR34A is common in secondary-school and first-year university syllabi. It links to neighbouring topics Genes on human chromosome 1, Human chromosome 1 gene stubs, so understanding it makes those chapters shorter.
In everyday life: Look for MIR34A 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 MIR34A in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what MIR34A 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 MIR34A out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is MIR34A in simple terms?

MicroRNA 34a (miR-34a) is a microRNA that in humans is encoded by the MIR34A gene. Function microRNAs (miRNAs) are short (20–24 nt) non-coding RNAs that are involved in post-transcriptional regulation of gene expression in multicellular organisms by affecting both the stability and translation of m…

Why does MIR34A 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 MIR34A?

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 MIR34A.