biology

Inhibitor of DNA-binding protein

Inhibitor of DNA-binding protein 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 Inhibitor of DNA-binding protein rather than just read about it. In short: Inhibitor of DNA-binding/differentiation proteins, also known as ID proteins comprise a family of proteins that heterodimerize with basic helix-loop-helix (bHLH) transcription factors to inhibit DNA binding of bHLH proteins. ID proteins also contain the HLH-dimerization domain but lack the basic DNA-binding domain and thus regulate bHLH transcription factors when they heterodimerize with bHLH proteins.

Key takeaways

Inhibitor of DNA-binding protein belongs to biology; place it in that map before memorising details.
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Reproduce the core statement of Inhibitor of DNA-binding protein from memory before moving on to harder problems.

Reference excerpt

Inhibitor of DNA-binding/differentiation proteins, also known as ID proteins comprise a family of proteins that heterodimerize with basic helix-loop-helix (bHLH) transcription factors to inhibit DNA binding of bHLH proteins. ID proteins also contain the HLH-dimerization domain but lack the basic DNA-binding domain and thus regulate bHLH transcription factors when they heterodimerize with bHLH proteins. The first helix-loop-helix proteins identified were named E-proteins because they bind to Ephrussi-box (E-box) sequences. In normal development, E proteins form dimers with other bHLH transcription factors, allowing transcription to occur. However, in cancerous phenotypes, ID proteins can regulate transcription by binding E proteins, so no dimers can be formed and transcription is inactive. E proteins are members of the class I bHLH family and form dimers with bHLH proteins from class II to regulate transcription. Four ID proteins exist in humans: ID1, ID2, ID3, and ID4. The ID homologue gene in Drosophila is called extramacrochaetae (EMC) and encodes a transcription factor of the helix-loop-helix family that lacks a DNA binding domain. EMC regulates cell proliferation, formation of organs like the midgut, and wing development. ID proteins could be potential targets for systemic cancer therapies without inhibiting the functioning of most normal cells because they are highly expressed in embryonic stem cells, but not in differentiated adult cells. Evidence suggests that ID proteins are overexpressed in many types of cancer. For example, ID1 is overexpressed in pancreatic, breast, and prostate cancers. ID2 is upregulated in neuroblastoma, Ewing’s sarcoma, and squamous cell carcinoma of the head and neck.

Function ID proteins are key regulators of development where they function to prevent premature differentiation of stem cells. By inhibiting the formation of E-protein dimers that promote differentiation, ID proteins can regulate the timing of differentiation of stem cells during development. An increase in ID expression is seen in embryonic and adult stem cells. ID proteins also promote cell cycle progression, delaying senescence, and help facilitate cell migration. In contrast, inappropriate regulation of ID proteins in differentiated cells can contribute to tumorigenesis. Generally, IDs function as oncogenes. When ID proteins are overexpressed, cell proliferation is enhanced and cells become insensitive to growth factor depletion. Expression of ID proteins in neurons halts neuron axon growth and allows elongation of neurons. Knockout mouse data show that ID genes are essential for heart development. There is some controversy surrounding the ID proteins and their role in cancer, but overexpression is seen in most tumor types. There are a few exceptions, for example, an increase in ID1 expression in brain cancer is correlated with a better prognosis, while a decrease in ID4 expression in colon and rectal cancers is linked to a poorer prognosis. ID proteins can bind E-proteins, preventing them from binding bHLH proteins and halting transcription, a case often seen in cancerous phenotypes.

Subtypes Humans express four types of Id proteins (called ID1, ID2, ID3, and ID4). A recent publication in Cancer Research (August 2010) has shown that ID1 can be used to mark endothelial progenitor cells which are critical to tumour growth and angiogenesis. This publication has demonstrated that targeting ID1 resulted in decreased tumour growth. Therefore, ID1 could be used to design a novel cancer therapy. Perk, Iavarone, and Benezra, (2005), reviewed fifteen studies and compiled a list of the phenotypic effects of each ID gene when knocked out in mice. When ID1 was knocked out, a defect in T-cell migration was seen. A knockout of ID2 showed that 25% of mice died perinatally, and those born lacked lymph nodes and showed defects in mammary proliferation. Generally, normal development was seen in mice with an ID3 knockout, but they did have a defect in B-cell proliferation. Neural defects and premature differentiation were seen in mice lacking ID4. Knockout of both ID1 and ID3 resulted in embryonic lethality due to brain hemorrhages and abnormalities in cardiac development.

References

External links Inhibitor+of+Differentiation+Proteins at the U.S. National Library of Medicine Medical Subject Headings (MeSH)

Worked examples

Example 1 — a first encounter with Inhibitor of DNA-binding protein

Start with the simplest possible case. Write down what Inhibitor of DNA-binding protein 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 Inhibitor of DNA-binding protein 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 Inhibitor of DNA-binding protein 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 Inhibitor of DNA-binding protein

In research: Inhibitor of DNA-binding protein 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 Inhibitor of DNA-binding protein 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: Inhibitor of DNA-binding protein is common in secondary-school and first-year university syllabi. It links to neighbouring topics Enzyme inhibitors, Protein families, so understanding it makes those chapters shorter.
In everyday life: Look for Inhibitor of DNA-binding protein 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 Inhibitor of DNA-binding protein in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Inhibitor of DNA-binding protein 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.
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Frequently asked questions

What is Inhibitor of DNA-binding protein in simple terms?

Why does Inhibitor of DNA-binding protein 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 Inhibitor of DNA-binding protein?

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 Inhibitor of DNA-binding protein.