science

Selective factor 1

Selective factor 1 is a science 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 Selective factor 1 rather than just read about it. In short: Selective factor 1 (also known as SL1) is a transcription factor that binds to the promoter of genes and recruits a preinitiation complex to which RNA polymerase I will bind to and begin the transcription of ribosomal RNA (rRNA). Discovery SL1 was discovered by Robert Tjian and his colleagues in 1985 when they separated a HeLa cell extract into two functional fractions.

Key takeaways

Selective factor 1 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Selective factor 1 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Selective factor 1 from memory before moving on to harder problems.

Reference excerpt

Selective factor 1 (also known as SL1) is a transcription factor that binds to the promoter of genes and recruits a preinitiation complex to which RNA polymerase I will bind to and begin the transcription of ribosomal RNA (rRNA).

Discovery SL1 was discovered by Robert Tjian and his colleagues in 1985 when they separated a HeLa cell extract into two functional fractions. One factor has RNA polymerase I activity, but no ability to initiate accurate transcription of a human rRNA template. This transcription factor, SL1, showed species specificity. That is, it could distinguish between the human and mouse rRNA promoter, and added increasing amount of human template at the expense of the mice template. Tijian and coworkers went on to show that by footprinting a partially purified polymerase 1 preparation could bind to the human rRNA promoter. In particular it causes a footprint over a region of the UCE called A site. This binding is not due to polymerase I itself but to a transcription factor called upstream binding factor, UBF.

Function SLI functions in assembling the transcription preinitiation complex. It is also a major determinant of species-specificity in ribosomal RNA gene transcription. Research suggests that UBF and SL1 act synergistically to stimulate transcription. Recent investigation also suggests that SL1 is a target for cancer therapy.

Structure SL1 is composed of the TATA-binding protein and at least four TAF (TATA box-binding protein-associated factor) subunits (TAF1A, TAF1B,TAF1C and TAF1D). It is therefore possible to inhibit SL1 activity with anti-TBP antibodies.

See also RNA polymerase I RNA polymerase III Transcription preinitiation complex

References

Illustrations

Worked examples

Example 1 — a first encounter with Selective factor 1

Start with the simplest possible case. Write down what Selective factor 1 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Selective factor 1 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 Selective factor 1 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 Selective factor 1

In research: Selective factor 1 appears in science 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 Selective factor 1 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: Selective factor 1 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Transcription factors, so understanding it makes those chapters shorter.
In everyday life: Look for Selective factor 1 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 Selective factor 1 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Selective factor 1 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 Selective factor 1 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Selective factor 1 in simple terms?

Why does Selective factor 1 matter?

Because it connects several science 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 Selective factor 1?

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 Selective factor 1.