Eukaryotic Transcriptional Regulation Flashcards
Different embryonic cells will have different fates depending on the _____ exchanged and which _____ are switched on or off
signals, genes
____________ creates various cell types that can be organized into _________
Gene regulation, tissue types
Although cells may have the same ________ gene regulation differences can lead to altered _________
genomes, proteomes
What are transcription factors?
Proteins that bind to specific DNA sequences and control transcription, and determine cell type pathways
What in dividing embryos leads to stem cells becoming speciallized cells?
Gene expression patterns and regulation, and extracellular cues
By controlling which genes are _____ along the chromosome, there are many _______ types and ______ found in specific tissues
Active, cell types, specific proteins
How to eukaryotes control gene expression (general)
Use of promoters and enhancers for each specific gene; no operons
How does tightly wound heterochromatin affect whether a gene is expressed?
Genes within tightly wound heterochromatin are usually not expressed unless it is unwound from the histone proteins
What is a nucleosome?
8 histone proteins
Chromatin must be unwound through _________ __________ when a _________ protein or _________ __________ is able to bind to an accessible _______ site, leading to further chromatin remodelling
Chromatin remodelling, activator, transcriptional factor, enhancer
How is DNA wound around histones?
Interactions between negatively charged phosphates in DNA and positively charged histone tails
What does the coactivator enzyme histone acetyltransferase do during chromatin remodelling?
Reacts with activator proteins, attaches acetyl groups to lysine amino acids along the positive tails , reducing the positive charge and loosening them so transcription factors can bind
What other chemical modificaitons can alter histone tails?
-Methylation of lysine and arginine
-Phosphorylation of serine and threonine
Acetylation and methylation with a single methyl group leads to…
Transcriptional activation
Methylation with three methyl groups leads to…
repression of transcription
What are the 4 transcriptional factor DNA binding structures?
-basic-helix-loop-helix
-helix-turn-helix
-zinc finger
-leucine zipper regions
Most transcriptional factors have a _______________ that fits within major ______ of DNA due to molecular interactions between amino acids in the alpha helix and the ______________ of nitrogenous bases
alpha-helical domain, grooves, functional group
What happens when a strong enough interaction is made by transcription factors?
TF assumes a conformaiton that allows the recruitment of other transcription factors, RNA polymerase, and activation of transcription at the target gene
What are the specific sequences required to initiate transcription at promoter regions?
Cissequences
What is found in the core promoter?
TATA box, BRE region, and transcriptional start sites
What usually recognizes the TATA box?
TATA binding protein subunit of the transcription factor TFIID
What binds the BRE region?
TFIIB general transcription factor
What is the purpose of the TATA and BRE binding transcription factors?
Assists with the assembly of the transcription initiation complex
How do enhancer region bound transcription factors contribute to RNA polymerase recruitment and initiation?
-Facilitates formation of the transcription complex
-Interact witht he basal machinery at the promoter to enhance transcription
-When DNA loops, they are connected to the proteins at the core promoter
What is the function of adapter/mediator proteins?
They connect proteins bound the the enhancer region withe proteins at the core promoter, so they can interact with RNA polymerase and basal transcriptional machinery at the core promoter
In eukaryotes, what are the sequences that bind transcriptional repressors and halt transcription called?
Silencer regions
_________________ differentiate into red blood cells that contain ___________ that can bind O2
Blood cell progenitors, haemoglobin
How does blood cell progenator gene activation differ in fetuses and adults?
-Both have 2 alpha-globin proteins making up half their tetrametric haemoglobin proteins
-Fetuses have 2 gamma-globin proteins
-Adults have 2 beta-globin proteins
How does gamma-globin differ from beta-globin?
Gamma-globin can bind O2 better, allowing fetuses to sequester enough oxygen in the womb
How is the beta globin gene inhibited in fetuses?
The chromatin is wound around the beta globin gene, while the gamma-globin gene is left open
How is the gamma globin gene repressed in adults?
Transcription factors can silence or repress gamma-globin and activate beta-globin
What is a CpG island and how can it inhibit transcription?
A string of cytosine and guanine
The methylation of the cytosines in a CpG island near promoter sequences can inhibit transcription by preventing DNA binding proteins from recognizing and binding the promoter sequence
The methylation state of promoters is _____, channging to ________/____________ cues
dynamic, environmental/developmental
Methylaiton state is _________ from mother cells to daughter cells
heritable
Which protein can only bind to methylated DNA? What do they do?
Histone deacetylases
Bind to methylated DNA and promote removal of acetyl groups from neighbouring histones
What does the deacetylation of histones do?
-Allows nucleosomes to reassemble
-Can lead to masking enhancer and promoter sequences, repressing transcription
Eukaryotic chromatin is wound in a default _____ conformation, genes are only transcribed when chromatin is remodelled to expose ___________
off, promoter sequences
Prokaryotyes have a default _____ conformation
on
