Regulation of Gene Expression in Eukaryotes
I. Spatial and temporal regulation
A. Spatial:
1. Not every gene product is required in every tissue
2. Part of the complexity of multicellular organisms
a) Ex. Tubulin proteins in Arabidopsis
B. Temporal
1. Not every gene product is required at every time
2. Most dramatically seen during development
a) Ex. Globin ɑ2β2 tetramers in animals
II. Ways of regulating gene expression
A. Controlling transcription of DNA
1. More complex than prokaryotic - signal transduction
2. Protein mediators are called transcription factors
B. mRNA splicing: one gene, multiple products
1. Two introns spliced together - exon loss
2. Alternate intron excised - altered exon
III. Three examples of eukaryotic gene induction
A. Induction by environmental factors
1. Temperature: the heat-shock genes
a) HSPs stabilize cellular actions at high temperatures
b) Best studied is HSP70 induction in Drosophila
(1) Occurs when temp. Exceeds 33° C
(2) HSP70 is induced ~10,000 fold
(a) Pol is “paused” - fires once every 4 minutes
(b) HSF trimer activates Pol - fires every 4 sec
IV. Eukaryotic Gene regulation
A. Sequences and proteins
1. Basal txn factors bind with RNAP at gene promoters, but what regulates
RNAP binding/elongation?
2. TXN factors that bind to enhancers
a) Characteristics of enhancers
(1) Act over long distances (up to several thousand bp)
(2) Influence independent of orientation
(a) Essentially a landing pad for proteins
(b) There isn’t really a backwards for this portion
(3) Can be found up or downstream - bidirectional?
(a) Enhancer can be anywhere in 3D space, can be
downstream
(b) Maybe working on multiple genes?
b) Physical interaction between enhancer and promoter sequences
suggests a “looping mechanism”
3. TXN factors have at least two domains
I. Spatial and temporal regulation
A. Spatial:
1. Not every gene product is required in every tissue
2. Part of the complexity of multicellular organisms
a) Ex. Tubulin proteins in Arabidopsis
B. Temporal
1. Not every gene product is required at every time
2. Most dramatically seen during development
a) Ex. Globin ɑ2β2 tetramers in animals
II. Ways of regulating gene expression
A. Controlling transcription of DNA
1. More complex than prokaryotic - signal transduction
2. Protein mediators are called transcription factors
B. mRNA splicing: one gene, multiple products
1. Two introns spliced together - exon loss
2. Alternate intron excised - altered exon
III. Three examples of eukaryotic gene induction
A. Induction by environmental factors
1. Temperature: the heat-shock genes
a) HSPs stabilize cellular actions at high temperatures
b) Best studied is HSP70 induction in Drosophila
(1) Occurs when temp. Exceeds 33° C
(2) HSP70 is induced ~10,000 fold
(a) Pol is “paused” - fires once every 4 minutes
(b) HSF trimer activates Pol - fires every 4 sec
IV. Eukaryotic Gene regulation
A. Sequences and proteins
1. Basal txn factors bind with RNAP at gene promoters, but what regulates
RNAP binding/elongation?
2. TXN factors that bind to enhancers
a) Characteristics of enhancers
(1) Act over long distances (up to several thousand bp)
(2) Influence independent of orientation
(a) Essentially a landing pad for proteins
(b) There isn’t really a backwards for this portion
(3) Can be found up or downstream - bidirectional?
(a) Enhancer can be anywhere in 3D space, can be
downstream
(b) Maybe working on multiple genes?
b) Physical interaction between enhancer and promoter sequences
suggests a “looping mechanism”
3. TXN factors have at least two domains
