10 | Nucleosome Flashcards
Histones
Largest protein component of chromatin.
Highly conserved, basic and octameric conplexes around which DNA wraps to form a nucleosome.
Chromatin
The material constituting a chromosome, both DNA and protein. The mass of each being roughly equal in contribution.
Nucleosome
Condensed form of DNA wrapped around a histone protein.
Core histones (4)
H2A, H2B, H3, H4
Cross-linking (Protein)
Method identifying which proteins are adjacent to each other in an oligomer.
Histone octomer
Nucleosome packaging unit comprised of two copies of each core histone
Histone-fold motif
Three α-helices linked by two short loops
Histone tail
Flexible, N-terminal of histone with a mostly disordered crystal structure
Naked DNA
DNA unprotected by protein
Chomatosome
Partially digested DNA fragment including core histones and H1.
Linker histone
H1 (only 1 per chromatosome)
30 nm Filament
Condensed form of nucleosome found under certain conditions, such as a highly ionic environment.
Solenoid Model
(also known as one-start helix model)
30 nm form that is spiral-shaped where flat sides of adjacent nucleosome disks are next to each other.
Zig-zag Model
(also known as two-start helix model)
30 nm form where zigzag histone pairs stack and twist about a central axis.
Epigenic inheritance
Inherited genetic properties not encoded in DNA.
Classes of protein that alter nucleosome arrangement (2)
(1) Chromatin remodeling complexes
(2) Histone modifying enzymes
ChIP Sequence
Technique using chromatin immunoprecipitation followed by DNA sequencing that determines the position of a nucleosome within the genome
Histone chaperones
Acidic proteins required to assemble histone octamers within DNA.
Histone acetyltransferase (HAT)
Enzyme that performs acetylation at Lys residue to improve accessibility and transcriptional activation.
Chromodomain
Motif possessed by proteins that bind to methylated Lys residues.
Histone code
The successive histone driven modifications that drive transcriptional activation.
