CENP-A AND CENTROMERES (Page 39-41)

; [How many H2A variant genes exist?]

Many H2A variant genes exist, including H2A1 (H2AC11/13/15/16/17), H2A1B/E (H2AC4/8), H2A1C (H2AC6), H2A1D (H2AC7), H2A1H (H2AC12), H2A1J (H2AC14), H2A2A (H2AC18/19), H2A2B (H2AC21), H2A2C (H2AC20), H2A3 (H2AC25).

; [What are the structural domains of H2A variants?]

N-terminal tail, Histone fold domain, and C-terminal tail.

; [What is the relationship between histone variants and chaperones?]

Histone variants and their chaperones have diverse functions in chromatin regulation.

; [Where is CENP-A selectively incorporated?]

CENP-A is selectively incorporated into chromatin at centromeres through the chaperone protein HJURP.

; [What is the function of CENP-A?]

CENP-A is crucial for the assembly of the kinetochore complex that drives mitosis.

; [What epigenetic features characterize centromeres?]

Centromeres (CENP-A bound sites) are low in DNA methylation and H3K9me3. The regions flanking centromeres (peri-centromeric regions) are highly enriched in DNA methylation and H3K9me3. These epigenetic modifications aid the specification of centromere sites and promote mitotic function.

; [How does CENP-A nucleosome structure compare to canonical H3 nucleosomes?]

Structurally, CENP-A nucleosomes are highly similar to those with canonical H3. However, CENP-A has variations in an N-terminal region that result in a shorter alpha-helix and weaker DNA-nucleosome interactions.

; [What happens when the CENP-A N-terminus is replaced with canonical H3 N-terminus?]

Replacing the CENP-A N-terminus with the canonical H3 N-terminus results in major defects in mitosis, demonstrating the critical importance of the shortened N-terminal helix for CENP-A function during mitosi