ADL Lecture 4: 15 Flashcards
Regulation of Gene Expression (Eukaryotes)
Activator proteins
bind regulatory sequences to stimulate transcription
repressor proteins
bind other sequences to hinder transcription
What are the differences in gene regulation between eukaryotes/prokaryotes?
Eukaryotes:
- processes of transcription and translation are uncoupled
- many genes are alternatively spliced to yield dif. products
- genes are typically mono-cistronic
- gene regulated by separate/mult. promoters
- regulatory proteins are found in large complexes
What are the five steps of Gene regulation in eukaryotes?
- Transcriptional regulation
- mRNA processing
- . Regulation of mature mRNA
- Translation
- Post-transltion
What are the five sub-stages of transcriptional regulation?
a. Reg. proteins + TFs bind to consensus DNA sequences (promoter region) to facilitate transcription.
b. more reg. DNA sequences (enhancers/silencers) bind reg. proteins to facilitate transcription of specific genes in each cell type.
c. open chromatin struc. favorable for transcription formed by protein action
d. Other promoters utilized in different cell types to produce different pre-mRNA molecules
e. Methylation of DNA inhibits transcription
What are the four sub-stages of mRNA processing?
a. capping of 5’ end, polyA of 3’ end, & intron splicing modify pre-mRNA
b. Other capping/PolyA sites can be used in diff. cell types
c. Other splicing produces diff. mature mRNA molecules from some cell types
d. RNA editing modifies base sequences of mRNA
What are the four sub-stages of Regulation of mature mRNA?
a. Translational regulatory proteins bind mature mRNA to delay translation initiation
b. RNA silencing by RNA interference blocks mature mRNA translation
c. Transport of mature mRNA to cytoplasm is regulated
d. Regulation of mRNA stability
What is the sub-stage of translation?
making of mRNA delays or prevents translation
What are the three sub-stages of Post-translation?
a. Polypeptides are processed and modified in Golgi body before transportation out of cell.
b. Reg. molecules bind to a Polypeptide to alter function
c. reg. protein stability
Structural motif
The characteristic three dimensional structure of a protein, sometimes obtained from crystal structure data (most common elements of structural motifs are alpha helices and others that form function domains of proteins)
functional domain
protein region with a specific function or interaction; allow recognition and binding of specific DNA sequences
Helix-loop-helix
two alpha helices separated by loop in each polypeptide. 2 polypeptides join to form a DNA binding dimeric protein. 1 alpha helix from each dimer binds regulatory DNA
Leucine Zipper
2 alpha helices, 1 containing mult. leucine amino acids. 2 polypeptides form functional dimeric protein. Leucine-containing helices fave one another and interdigitate to form the “zipper” + other helix of each polypeptide binds DNA
Homeodomain
3 helices form single function polypeptide & longest helix interacts with regulatory DNA sequences
Zinc finger
Protruding loops or “fingers” containing about 24 amino acids each contain a central molecule of zinc bound to 2 cysteine and 2 histidine amino acids. 2/3 zinc fingers form in each polypeptide & each finger interacts w/ regulatory DNA
What are the three sets of regulatory DNA sequences involved in eukaryotic gene regulation?
- core promoter region
- various proximal elements
- enhancer sequences
Core promoter region
contains the TATA box; immediately adjacent to start of transcription; bind RNA polymerase II and assoc. TFs
Various proximal elements
upstream of core promoter region; bind regulatory proteins
enhancer sequences (enhancers)
bind regulatory proteins/interact with proteins bound to other promoter segments. Can be upstream/downstream or “in” genes they regulate and can be very far away
cis-actiing regulatory sequences
Sequences to which proteins bind to regulate transcription of genes located on the same chromosome as the sequences
Trans-acting regulatory proteins
Proteins that act in trans by binding to cis-acting reg. sequences and consequently regulating nearby genes, either by activating or repressing transcription. (often referred to as TFs)
Enhanceosomes
at enhancers; mult. proteins form large complexes
Enhanceosomes action
- direct DNA bending into loops that allow enhaceosome proteins to interact with RNA polymerase and TFs at core promoter and proximal promoter elements
- controls timing/location of gene transcription
UAS
upstream activator sequence
