regulation

• What determines the cellular concentration of a protein?

  A delicate balance of at least seven processes
• What are the seven processes that determine protein concentration?

  1. Transcription
  2. Post-transcriptional modification of mRNA
  3. mRNA degradation
  4. Translation
  5. Post-translational modification of proteins
  6. Protein targeting and transport
  7. Protein degradation
• At which step can regulation occur in transcription?

  At any step of transcription
• What is tightly regulated during transcription initiation?

  RNA polymerase binding to the promoter

  
• How does the promoter sequence affect transcription initiation?

  Differences in promoter sequence affect RNA polymerase binding and transcription initiation frequency
• What role does protein binding to the operator play in transcription?

  It can activate or repress transcription

  
• What are the two types of genes based on expression regulation?

  • Housekeeping genes: continuously expressed and required at all times
  • Regulated genes: expression increases or decreases based on cellular needs
• What is induction in gene expression?

  The process by which gene products increase in concentration under particular molecular circumstances
• What are activators in gene expression?

  Proteins that enhance RNA polymerase-promoter interaction
• What is repression in gene expression?

  The process by which gene products decrease in concentration in response to a molecular signal
• What is the default state of genes in bacteria?

  Generally "on"
• How is gene transcription limited in bacteria?

  By a repressor

  
• What is the default state of most genes in eukaryotes?

  Generally "off"
• What is required for gene transcription in eukaryotes?

  Chromatin modification followed by the action of transcription activators
• How does chromatin structure affect eukaryotic promoters?

  Access to eukaryotic promoters is restricted by chromatin structure

  
• What role do lncRNAs play in eukaryotic transcriptional regulation?

  They regulate nucleosome positioning and chromatin structure
• What are the two forms of chromatin and their characteristics?

  • Heterochromatin: much more condensed, transcriptionally inactive
  • Euchromatin: less condensed, sometimes transcriptionally active

  
• How are transcriptionally active regions of the chromosome distinguished?

  By the position of nucleosomes, presence of histone variants, and covalent modification of histones
• When does transcription occur in relation to chromatin structure?

  When the chromatin is in open or euchromatin conformation

  
• What is positive regulation in gene expression?

  Any process that activates or increases the frequency, rate, or extent of protein formation
• What are the components of positive regulation in gene expression?

  1. Transactivators or transcriptional activators
  2. Structure regulators
  3. Chromatin remodeling
  4. Coactivators (“Mediator”)
  5. Basal transcription factors (initiation factors)

  
• What mediates post-transcriptional regulation?

  RNA interference
• How do translation repressors function?

  They bind to specific sites on the mRNA to block or slow translation
• What can regulate eukaryotic gene expression?

  Intracellular and extracellular signals
• What is epigenetics?

  • Study of stable phenotypic changes that do not involve alterations in the DNA sequence
  • Changes are reversible and can affect gene expression
• What is an example of an epigenetic change in eukaryotic biology?

  The process of cellular differentiation during morphogenesis
• What are the two main types of modifications in epigenetics?

  DNA methylation and histone modifications

  
• What happens to totipotent stem cells during morphogenesis?

  They become various pluripotent cell lines of the embryo