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Chapter 28
Regulation of Gene Expression
31
Biochemistry
Undergraduate 3
04/18/2016

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Term
euchromatin
Definition
the less condensed chromatin
Term
chromatin remodeling
Definition
the transcription-associated structural changes in chromatin
Term
SWI/SNF
Definition
found in all eukaryotic cells & contain at least six core polypeptides that together remodel chromatin so that nucleosomes become more irregularly spaced
Term
NURF
Definition
remodels chromatin in ways that complement & overlap the activity of SWI/SNF
Term
SWR1
Definition
a family of ATP-dependent remodeling enzymes
Term
histone acetyltransferases (HATs)
Definition
enzymes that acetylate particular Lys residues
Term
histone deacetylases (HDACs)
Definition
reduces the activity of acetylation of nucleosomes when transcription of a gene is no longer required; works as part of a general gene-silencing process that restores the chromatin to a transcriptionally inactive state
Term
What is the relationship between enhancers & upstream activator sequences (UASs)?
Definition
The additional regulatory sequences, generally bound by transcription activators, are usually called ENHANCERS in higher eukaryotes & UASs in yeast
Term
5 types of proteins whose binding is required for successful binding of active RNA polymerase II holoenzyme at one of its promoters
Definition
1. transcription activators
2. architectural regulators
3. chromatin modification & remodeling proteins
4. coactivators
5. basal transcription factors
Term
high mobility group (HMG)
Definition
play an important structural role in chromatin remodeling & transcriptional activation
Term
mediator
Definition
a major eukaryotic coactivator consisting of 20 to 30 or more polypeptides in a protein complex
Term
What is the relationship between preinitiation complex (PIC) & TATA-binding protein (TBP)?
Definition
The first component to bind in the assembly of a PIC at the TATA box of a typical Pol II promoter is the TBP
Term
hormone response elements (HREs)
Definition
a highly specific DNA sequence to which the hormone-receptor complex binds in order to act; alters gene expression
Term
steroid receptor RNA activator (SRA)
Definition
a coactivator with which hormone receptors activate transcription; an ~700 nucleotide RNA
Term
CRE-binding protein (CREB)
Definition
a nuclear protein that is phosphorylated by the catalytic subunit of protein kinase A
Term
4 main mechanisms of translational regulation in eukaryotes
Definition
1. translation initiation factors are subject to phosphorylation by protein kinases
2. some proteins bind directly to mRNA & act as translational repressors, many of them binding at specific sites in the 3' untranslated region
3. binding proteins, present in eukaryotes form yeast to mammals, disrupt the interaction eIF4E & eIF4G
4. RNA-mediated regulation of gene expression often occurs at the level of translational repression
Term
HCR (hemin-controlled repressor)
Definition
a protein kinase; gets activated to catalyze the phosphorylation of eIF2
Term
small temporal RNAs (stRNAs)
Definition
the many miRNAs that are present only transiently during development
Term
ncRNAs
Definition
all RNAs that do not encode proteins (including rRNAs & tRNAs)
Term
constitutive gene expression
Definition
unvarying expression of a gene
Term
regulated gene expression
Definition
for gene products whose cellular levels rise & fall in response to molecular signals
Term
What is the relationship between inducible & induction?
Definition
Gene products that increase in concentration under particular molecular circumstances are referred to as INDUCIBLE; the process of increasing their expression is INDUCTION
Term
What is the relationship between repressible & repression?
Definition
Gene products that decrease in concentration in response to a molecular signal are referred to as REPRESSIBLE, and the process is called REPRESSION
Term
3 types of proteins that regulate transcription initiation by RNA polymerase
Definition
1. specificity factors
2. repressors
3. activators
Term
negative regulation
Definition
regulation by means of a repressor protein that blocks transcription
Term
effector
Definition
a molecular signal which regulates repressor binding to DNA; usually is a small molecule or a protein that binds to the repressor & causes a conformational change
Term
positive regulation
Definition
activators provide a molecular counterpoint to repressors by binding to DNA & enhancing the activity of RNA polymerase at a promoter
Term
architectural regulators
Definition
proteins that facilitate looping; bind to intervening sites & facilitate the looping of DNA
Term
operon
Definition
the gene cluster & promoter plus additional sequences that function together in regulation
Term
2 DNA-binding motifs that play prominent roles in the binding of DNA by regulatory proteins
Definition
1. helix-turn-helix
2. zinc finger
Term
combinatorial control
Definition
the phenomenon through which appropriate regulation of different genes is accomplished by utilizing different combinations of a limited repertoire of transcription factors at each gene
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