Question

Explain how the acetylation of core histones may loosen chromatin packing.

Short answer

Histone acetylation loosens chromatin packing by introducing acetyl groups onto the lysine residues of histones. This neutralizes the positive charge, reducing the binding between histones and the negatively charged DNA. The consequent looser chromatin structure facilitates the access of transcription factors to the DNA, promoting gene expression.

Step-by-step solution

Understanding Histone acetylation

Start by understanding what histone acetylation is. Histone acetylation is a process that plays a key role in gene regulation. It occurs when acetyl groups are transferred to the lysine residues in the N-terminal tail of the histone protein. This process is facilitated by enzymes called histone acetyltransferases (HATs).

Effect on Chromatin Structure

Explain how histone acetylation affects the chromatin structure. The addition of acetyl groups neutralizes the positive charge of the lysines and decreases the binding between the histones and the negatively charged DNA, resulting in a looser chromatin structure.

Relation to Gene Expression

Explain how this alteration affects gene expression. A looser chromatin structure makes DNA more accessible to transcription factors and other proteins needed for gene expression, thereby promoting transcriptional activation. Thus, acetylation of histones generally correlates with regions of active gene transcription.