CHAPTER 15 Flashcards
(25 cards)
What are transcription factors?
Transcription factors are proteins that influence RNA polymerase’s ability to transcribe a gene.
Two main types of transcription factors
- General transcription factors
- Regulatory transcription factors
General transcription factors
required for the binding of RNA polymerase to the core promoter and for basal transcription.
Regulatory transcription factors
regulate the transcription rate of target genes and influence RNA polymerase’s ability to begin transcription.
What are control elements in gene regulation?
Control elements, also known as cis regulatory elements, are sequences located near the core promoter.
How are control elements recognized?
They are recognized by regulatory transcription factors, which can either increase (activators) or decrease (repressors) the rate of transcription.
What roles do activators and repressors play in transcription?
-Activators: Proteins that increase transcription rates by binding to enhancers.
-Repressors: Proteins that decrease transcription rates by binding to silencers.
What is combinatorial control in gene regulation?
Combinatorial control refers to the regulation of most eukaryotic genes by multiple factors.
What does combinatorial control in gene regulation include?
- One or more activators stimulate transcription.
- One or more repressors inhibiting transcription.
- Modulation by small effector molecules, protein-protein interactions, or covalent modifications.
What are domains in transcription factors?
Domains are regions of transcription factor proteins with specific functions (e.g., DNA-binding, binding sites for effector molecules).
What are motifs in transcription factors?
A motif is a domain or part of a domain that has a similar structure across various proteins.
Enhancers
Binding of a transcription factor increases transcription rates (up-regulation).
Silencers
Binding of a transcription factor decreases transcription rates (down-regulation).
Mediator
A complex that interacts with transcription factors and RNA polymerase, facilitating transcription activation and repression.
TFIID
A general transcription factor that recruits RNA polymerase to the core promoter.
What are the three common ways to modulate the function of regulatory transcription factors?
- Binding of small effector molecules.
- Protein-protein interactions.
- Covalent modifications.
How do steroid hormones affect regulatory transcription factors?
Steroid hormones bind directly to their receptors, affecting gene transcription.
How does chromatin structure impact gene expression?
-Chromatin can exist in closed (tightly packed, inhibiting transcription)
-Open (accessible to transcription factors, allowing transcription) conformations
-Directly influencing the ability to express genes.
How do chromatin remodeling complexes alter gene expression?
They change nucleosome positions and compositions using ATP hydrolysis, making DNA more or less accessible for transcription.
What is DNA methylation and its effect on gene transcription?
DNA methylation is the covalent addition of methyl groups, usually inhibiting eukaryotic gene transcription. It is performed by DNA methyltransferases.
What are CpG islands and their role in gene regulation?
CpG islands are regions near gene promoters with high frequencies of CpG sites.
-In housekeeping genes, they are generally unmethylated, leading to expression,
-Tissue-specific genes, methylation can silence their expression.
What mechanisms regulate translation after mRNA synthesis?
-RNA-binding proteins that affect translation and degradation of mRNAs.
-Small RNAs (covered in Chapter 17).
-Iron Response Protein (IRP) illustrate these mechanisms.
How does the Iron Regulatory Protein (IRP) regulate iron uptake?
IRP binds to Iron Response Elements (IREs) in mRNAs for ferritin and transferrin receptor.
Low Iron
IRP binds to IRE, preventing ferritin translation.
