Questions and Answers
What is the primary role of general (basal) transcription factors?
Specific transcription factors can bind to regulatory sequences of any gene.
False
Define a transcription factor.
Any protein required to initiate or regulate transcription, other than RNA polymerase.
Transcription factors are identified to interact through specific amino acid side chains and base __________.
Signup and view all the answers
Approximately how many human transcription factors have been identified?
Signup and view all the answers
Match the following transcription factor types with their functions:
Signup and view all the answers
It takes approximately 10-20 weak interactions for a stable DNA-protein interface to form.
Signup and view all the answers
What is one mechanism by which transcription factors can achieve tissue-specific gene expression?
Signup and view all the answers
What is the purpose of spatio-temporal control of transcription factor expression?
Signup and view all the answers
Mis-regulation of transcription factor expression does not impact health.
Signup and view all the answers
Name one method used to identify transcription factors.
Signup and view all the answers
Transcription factors can be purified by affinity __________, using their property of binding specific DNA sequences.
Signup and view all the answers
Match the methods with their functions in studying transcription factors:
Signup and view all the answers
Which approach uses machine learning for binding site prediction?
Signup and view all the answers
What is the primary function of homeodomain proteins?
Signup and view all the answers
Zinc fingers consist of a structure maintained by Zn2+ ions.
Signup and view all the answers
What determines the DNA binding specificity of homeodomain proteins?
Signup and view all the answers
The leucine zipper forms a ____ helix due to the hydrophobic interactions among leucine residues.
Signup and view all the answers
Match the following protein motifs with their functions:
Signup and view all the answers
Which of the following correctly describes the structure of zinc fingers?
Signup and view all the answers
Substitution of leucine in the leucine zipper structure does not affect dimerization or DNA binding.
Signup and view all the answers
Name one example of a bHLH factor involved in muscle development.
Signup and view all the answers
What role do enhancers and silencers play in gene regulation?
Signup and view all the answers
Housekeeping genes are only found in specific tissues.
Signup and view all the answers
What determines the expression timing of tissue-specific genes?
Signup and view all the answers
The _____ is a DNA-binding motif found in many transcription factors.
Signup and view all the answers
Match the structural motifs with their characteristics:
Signup and view all the answers
How does the action of multiple transcription factors typically affect transcription?
Signup and view all the answers
Insulators serve to promote interference to neighboring transcription units.
Signup and view all the answers
What are ubiquitous transcription factors?
Signup and view all the answers
What is the primary role of transcription factors (TFs)?
Signup and view all the answers
Transcription factors can only activate transcription but cannot repress it.
Signup and view all the answers
Name one enzyme that has histone acetylase activity.
Signup and view all the answers
Transcription factors can also recruit __________ to the promoter to assist with transcription.
Signup and view all the answers
Match the transcriptional regulators with their functions:
Signup and view all the answers
Which activity is NOT a mechanism used by transcription factors to influence transcription?
Signup and view all the answers
Histone acetylation typically promotes transcription.
Signup and view all the answers
What is one effect of transcriptional repressors binding to DNA?
Signup and view all the answers
Study Notes
Transcription Factors Overview
- Transcription factors (TFs) are proteins essential for initiating or regulating transcription, excluding RNA polymerase.
- Two categories:
- General (basal) factors contribute to the formation of the basal transcription complex at the transcription start site.
- Specific factors modulate transcription of particular genes through binding to regulatory sequences, influencing protein synthesis variability.
- Approximately 1,639 human transcription factors have been identified.
TF Binding and Mechanism
- Transcription factors bind to DNA via specific amino acid interactions, involving weak associations; a stable complex requires 10-20 interactions.
- Access to DNA is restricted due to nucleosome wrapping; TFs utilize chromatin remodelers to facilitate binding.
- Binding sites may contain multiple weak interactions; synergy exists when multiple TFs interact to activate genes.
- TFs often function as dimers to enhance binding specificity; they primarily exist as monomers in solution.
Cis-Regulatory Sequences
- Key elements include enhancers and silencers located far from promoters, which facilitate or inhibit transcriptional activity.
- Insulators are present to prevent unintended interactions between nearby transcription units.
Housekeeping Genes
- Housekeeping genes exhibit consistent expression across all cell types, featuring binding sites for ubiquitous TFs.
- Activators work additively in non-linear fashion; e.g., if TF A increases transcription two-fold and TF B ten-fold, their combined effect can boost transcription significantly.
Tissue-Specific Genes
- Feature binding sites for both ubiquitous and tissue-specific TFs, example: globin genes interact with factors like SP1 and GATA-1.
- The context determines binding specificity; combinatorial control at the pre-initiation complex (PIC) decides gene expression outcomes.
Structural Motifs Classifying TFs
- Four primary structural motifs used to classify TFs:
- Helix-turn-helix: Found in both prokaryotic and eukaryotic TFs; recognition helix binds in major groove.
- Zinc fingers: Stabilized by Zn2+; diverse with multiple variations; example includes nuclear receptors.
- Leucine zippers: Characterized by leucine every seventh amino acid; forms dimers for specific DNA positioning.
- Helix-loop-helix: Involves dimerization; plays significant roles in muscle development and neurogenesis.
Mechanisms of TF Activation and Repression
- Activators interact with general TFs or RNA polymerase II to initiate transcription.
- Some TFs remodel chromatin structure via recruitment of histone-modifying enzymes (HATs and HDACs).
- Repression can occur by blocking activators or interfering with transcriptional complexes.
Regulated Expression of TFs
- Spatial and temporal control over TF expression is crucial for diverse gene-expression patterns across cell types.
- Misregulation can lead to diseases or malformations in development.
Experimental Methods for Investigating TFs
- Protein purification: Uses affinity chromatography to isolate TFs based on their DNA-binding capabilities.
- Footprinting techniques: Identify where TFs bind DNA by observing protected regions against nucleases.
- Reporter gene assays: Measure transcriptional activity in response to specific TFs.
- ChIP or CUT and RUN: Techniques for analyzing TF binding across the genome.
- Knock-down assays: Analyze transcriptional changes following the deletion of specific TFs.
- Machine learning and AI: Used for predicting TF DNA-binding motifs and their functions based on structural homology.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz assesses your understanding of eukaryotic transcription factors, including their definitions and classifications. You'll explore the differences between general and specific transcription factors, learn about experimental methods used to study them, and recognize structural motifs and mechanisms of action. Test your knowledge on key examples and concepts in this essential field of molecular biology.
