Chapter 17: Gene Regulation in Eukaryotes Flashcards
Gene Regulation
variation in the level of gene expression under different conditions
Transcription factor
broad category of proteins that influence the ability of RNA polymerase to transcribe DNA into RNA
General Transcription Factor (GTF)
one of several proteins that are necessary for a basal level of transcription at the core promoter in eukaryotes
Regulatory transcription factor
protein or protein complex that binds to a regulatory element and influences the rate of transcription vis RNA polymerase
Activator
enhances the rate of transcription by binding to an enhancer sequence
Repressor
prevent transcription from occurring by binding to a silencer sequence
combination of many factors regulates genes
combinatorial control
Modification of ____________ transcription factor proteins can occur in 3 common ways:
Regulatory
1. Binding of small-effector molecule
2. Protein-protein interactions
3. Covalent modifications
Binding of small effector molecule
ex. Promotes binding of DNA
Protein-protein interactions
ex. Formation of dimers controls transcription
Covalent modifications
ex. Attachment of a phosphate group to alter function
Chromatin can be in 2 conformations
- Closed conformation
- Open conformation
Closed Conformation (heterochromatin)
tightly packed conformation of chromatin that cannot be transcribed.
Open Conformation
(euchromatin)
Loosely packed chromatin structure that is capable of being transcribed.
Chromatin remodeling
change in chromatin structure that alters the composition of histones or the spacing of nucleosomes (or both).
Chromatin remodeling is carried out by…
ATP-dependent chromatin remodeling complexes
Eukaryotic gene regulation ________ __________ on these changes in chromatin structure
Depends partially
Eukaryotic gene regulation affects the ability of transcription factors to
gain access and bind to their target sequences
ATP-dependent chromatin-remodeling complexes change chromatin structure in 3 possible ways:
- Change in nucleosome position
- Histone eviction
- Replacement with histone variants
DNA Methylation
the phenomenon in which an enzyme covalently attaches a methyl group (-CH3) to a base (adenine or cytosine) in DNA
DNA methyltransferase
the enzyme that attaches methyl groups to adenine of cytosine bases.
DNA Methylation plays an important part in
- genomic imprinting
- X chromosome inactivation
- Suppression of repetitive element transcription and transposition
When DNA methylation is dysregualted it….
contributes to diseases like cancer
DNA methylation usually inhibits the
initiation of transcription
Most vertebrates and plants have
CpG islands
CpG islands
a group of CG sequences that may be cluster near a promoter of a gene. The methylation of the cytosine bases usually inhibits transcription
Housekeeping gene
a gene that encode a protein required in most cells of a multicellular organism
The cytosine bases in the CpG islands of housekeeping genes are __________ so they are
unmethylated, always expressed in all cell types
Tissue-specific gene
highly regulated and is expressed in a particular cell type
DNA methylation plays an important role in suppressing tissue-specific genes in…
the wrong tissue type
Methylation of CpG islands may enhance or prevent….
binding of regulatory transcription factors through silencing
___ _________ is heritable
DNA methylation
DNA will remain methylated through _____________ ___ _______ and production of ________ _____
subsequent DNA replication, daughter cells
unmethylated DNA will remain __________ through subsequent DNA replication and production of daughter cells
unmethylated
Modification example
Steroid hormones
Ultimate action of a steroid hormone
to affect gene transcription
in animals, steroid hormones act as _______ _________ that are synthesized by_________ _______ and secreted into the__________
signaling molecules, endocrine glands, bloodstream
hormones are taken up by cells that respond to these substances in different ways
- may influence metabolism of nutrients
*may influence development of secondary sexual characteristics and play a role in reproduction
1st effect of glucocorticoid in mammals
- hormone enters cytosol of cell through plasma membrane
2nd effect of glucocorticoid in mammals
- hormone binds to a glucocorticoid receptor
3rd effect of glucocorticoid in mammals
- receptor in a protein complex that releases HSP90 protein when the hormone binds to it
4th effect of glucocorticoid in mammals
- this exposes a nuclear localization site on the receptor that directs the receptor into the nucleus
5th effect of glucocorticoid in mammals
two receptors come together to form a dimer and travel into the nucleus
6th effect of glucocorticoid in mammals
dimer binds to a glucocorticoid response element (GRE)
7th effect of glucocorticoid in mammals
Activates transcription of adjacent gene, leading to synthesis of encoding protein (involved in metabolism)
