Gene Regulation in Eukaryotes Flashcards
(26 cards)
Do Eukaryotes have operons?
No- usually one gene per one promoter
- genes with similar functions often have similar promoters
- this allows a particular transcription factor to regulate a set of genes with similar functions
Different types of RNA polymerases
RNAP 1: rRNA
RNAP 2: mRNA
RNAP 3: tRNA
What binds to promoter DNA?
RNAP and 30+ transcription factors
Bacteria only have 1-2
Chromatin Remodeling
DNA must be accessible for transcription to occur
Heterochromatin
DNA tightly wrapped up by proteins
Inaccessible by RNAP
Euchromatin
DNA loosely wrapped, accessible by RNAP
Histones
DNA packaging proteins in eukaryotic cells: 4 proteins
The histone octamer is the basic unit of DNA compaction
From here, DNA can be assembled into compact chromatin
Compaction of DNA regulation
- Chemical modification of histones
- histone tails are POSITIVELY charged due to amino acid side chains
- DNA is NEGATIVELY charged
Histone acetylaton
Acetylating (+) charges on histones neutralizes thecharge:charge interactions between DNA and histones
THIS TENDS TO LOOSEN COMPACTION
Histone Acetyltransferases
tend to ACTIVATE transcription
Histone Deacetylases
remove acytly groups from histones
INCREASES compaction
DECREASES transcription
DNA methylation
occurs especially at cytosene CG repreats (CpG DNA)
DNA methyltransferases
ADD methylation to DNA
tends to REPRESS transcription
DNA demethylases
remove methylation from DNA
tend to ACTIVATE transcription
Transcription Factors
-bind first to the promoter of the eukaryotic gene
TFIID (TATA-binding protein)
- binds to TATA sequence (or similar) upstream from the transcription start site
- other transcription factors pile on
- together these factors recruit RNA polymerase to the promoter
The gene LacI(s) codes for a “super repressor” mutant. The protein product of this gene cannot bind lactose but can still bind DNA. How would the Lac Operon behave in a strain encoding this gene?
The strain would not transcribe the Lac operon in any situation
THe gene lacI(HTH) codes for a DNA binding domain mutant. THe protein product of this gene can bind lactose but cannot bind DNA. How would the Lac operon behave in a strain encoding this gene?
This strain would transcribe the Lac operon only in the absence of glucose but regardless of whether lactose is present or not
Imagine that you delete the gene for the catabolite activator protein (CAP). How would this CAP mutant behave?
This strain would not transcribe the Lac operon in any situation
Imagine that you delete the gene for adenylate cyclase, the enzyme in E. Coli that synthesizes cyclic AMP. How would this mutant behave?
This strain would not transcribe the Lac operon in any situation
Imagine that you delete the gene for adenylate cyclase, the enzyme in E. Coli that synthesizes cyclic AMP so that it constitutively synthesizes cyclic AMP regardless of glucose availability. How would this mutant behave?
This strain would transcribe the Lac operon only in the presence of lactose but regardless of whether glucose was present or absent
Imagine that you delete the gene encoding the repressor of the Trp operon. How would this mutant behave?
This strain would constitutively express teh Trp operon regardless of the presence of tryptophran
Imagine that you mutate the gene encoding the repressor of the Trp operon so that this repressor no longer binds tryptophan. How would this mutant behave?
This strain would not be able to express the Trp operon
Dehydration response element (DRE)
sequence of DNA in the promoters for a set of genes involved in for a set of genes involved in drought response in plants
