Ch.15: Gene regulation in eukaryotes I: Transcriptional and translational regulation Flashcards
How is Eukaryotic gene expression regulated?
just like bacteria - during transcription, translation or posttranslationally
Why Are General Transcription Factors and a Mediator Needed?
Required for the binding of the RNA polymerase to the core promoter and its progression to the elongation stage and are Necessary for basal transcription
Regulatory transcription factors
Serve to regulate the rate of transcription of target genes
and Influence the ability of RNA polymerase to begin transcription of a particular gene
There are two types of transcription factors in eukaryotes
What is the sequence that the activator bind to?
enhancer
What is the sequence that the repressor bind to?
silencer
Where are most response elements are located?
within a few hundred nucleotides upstream of the promote
Where do regulatory transcriptional activator and repressor proteins typically act?
at the general transcriptional factor TFIID
How does transcriptional activation or repression work via mediator?
-The carboxyl-terminal domain of RNA polymerase has to be phosphorylated for it to be active
-Mediator influences the ability of TFIIH to phosphorylate the carboxyl terminal domain (CTD) of RNA polymerase II
What are the 3 common ways the function of regulatory
transcription factors can be modulated?
Binding of a small effector molecule, Protein-protein interactions, Covalent modification
What is is an important parameter affecting gene expression in eukaryotes?
The three-dimensional packing of chromatin because it is a very dynamic structure that can alternate between two conformations
Closed Conformation
Chromatin is very tightly packed so Transcription may be difficult or impossible
Open Conformation
Chromatin is accessible to transcription factors so Transcription can take place
What are the 3 ways Chromatin remodeling complexes change chromatin structure?
Change in the position of nucleosomes, Eviction of histone octamers, Change in the composition of nucleosomes
What is a nucleosome
a histone octamer composed of two H3 histone proteins, two H4 histone proteins, two H2A histone proteins and two H2B histone proteins which is wrapped around DNA. The H1
histone protein, while not part of the nucleosome, serves as a linker between nucleosomes
What can happen to H1, H2A, H2B, H3, H4?
can be acetylated (DNA will be less tightly bound to the histone proteins), methylated (usually inhibits eukaryotic gene
transcription) or phosphorylated
