The Acetylation of Lysines on the Histone Tails …

Question

The acetylation of lysines on the histone tails …
A) loosens the chromatin structure because it adds positive charges to the histone.
B) recruits the heterochromatin protein HP1, resulting in the establishment of heterochromatin.
C) can be performed on methylated lysines only after they are first demethylated.
D) is sufficient for the formation of an open chromatin structure.
E) is a covalent modification and is thus irreversible.

Accepted Answer

Histone acetylation on lysine residues is generally an activating mark favoring more open chromatin structures (in contrast to what HP1 does), but this effect is mediated mostly through the recruited non-histone proteins that recognize this mark, not the chemical modification itself. The acetylation eliminates the positive charge on lysine, which helps-but is not sufficient alone-to loosen the nucleosome packaging. All known natural covalent modifications on the histone tails are reversible.