L4 - Chromatin Flashcards
What is haemoglobin made up of?
2 alpha and 2 beta-like globin chains
Role of HBA1 AND HBA2 genes in adults?
They produce each an alpha-globin protein
Role of HBB in adults?
It provides instructions for making a protein called beta-globin
Role of enhancers:
Enhancers are DNA-regulatory elements that activate transcription of a gene or genes to higher levels than would be the case in their absence. Activate transcription over long distances.
What do transcription factors bind to?
Specific DNA sequences called binding motifs, which are typically short sequences of nucleotides (e.g., ATCG) that are located within the promoter or enhancer regions of a gene.
What does H3K4me1 do?
It is a type of histone modification in which a methyl group is added to the lysine 4 residue of the histone H3 protein
Where is it usually present?
Enhancer regions
What is the significance of this?
The presence of H3K4me1 in enhancer regions is associated with the recruitment of transcription factors that bind to specific DNA sequences within the enhancer and activate transcription of the target gene.
What makes up a nucleosome?
Composed of eight histone proteins, which are organized into a protein octamer. The histone octamer consists of two copies each of four different histone proteins: H2A, H2B, H3, and H4.
What can alter the active structure of chromatin?
Chromatin remodelling complexes
What are the main differences between heterochromatin and euchromatin?
Two distinct types of chromatin that differ in their structure, gene density, gene expression patterns, and patterns of histone modifications. Euchromatin is less compact, more gene-rich, and more transcriptionally active, while heterochromatin is highly condensed, gene-poor, and often repressed or silenced.
What does H1 (Histone 1) do?
Histone H1 helps to organize and compact chromatin into higher-order structures by binding to the linker DNA and bringing adjacent nucleosomes into closer proximity.
How many base pairs of DNA are wrapped around the histone octamer?
147
What is an overall summary of TADs?
(Topologically Associating Domains)
Important structural features in the chromatin that help to organise and regulate gene expression by grouping together genes with related functions. They facilitate enhancer-promoter interactions+regulate long-range gene expression.
What is the role of Polycomb and Trithorax groups?
Two groups of proteins that play important roles in regulating gene expression during development in many organisms
What is the role of the Polycomb group (PcG)?
Involved in gene repression, which means they help to turn off genes. They modify the chromatin structure around the gene, making it more compact and less accessible.
What is the role of Trithorax group (TcG)?
Involved in gene activation, modifying chromatin in a way to make the gene accessible and easier to transcribe
What do ATP remodelling complexes do?
A family of proteins which regulate the structure and organisation of chromatin. These complexes use energy from ATP hydrolysis to move, reposition
How can trithorax (TRX) covalently modify histones?
A protein capable of methylating histone H3 on lysine 4
What is the name of the histone tail?
N-terminal tail (amino tail)
Are modifications on histones permanent?
No, they are reversible
What do histone orthographers do?
Enzymes which are involved in the synthesis of new histones
What do histone readers do?
Proteins that recognise and bind to specific histone modifications. They readers can then recruit other proteins to the chromatin, leading to changes in chromatin structure and gene expression.
What do histone writers do?
Enzymes that add or remove specific chemical modification to histone proteins
What are some examples of histone writers?
Histone acetyltransferases (HATs) and methyltransferases (HMTs)
What do histone erasers do?
Enzymes which remove specific histone modifications
What are some examples of histone erasers?
Histone deacetylases (HDACs) and histone demethylases (HDMs)
What does epigenome mean?
The overall epigenetic state of a cell
