Histone acetyltransferase

Definition

Histone acetyltransferase (HAT) is an enzyme that adds acetyl groups to specific lysine residues on histone proteins, leading to changes in chromatin structure and influencing gene expression. By modifying histones, HATs play a critical role in regulating the accessibility of DNA, thus impacting transcriptional activation and silencing.

5 Must Know Facts For Your Next Test

1. HATs are crucial for the formation of active chromatin by promoting a relaxed structure that allows transcription machinery access to DNA.
2. There are several families of HATs, categorized based on their sequence homology and functional characteristics, including Type A and Type B HATs.
3. The activity of HATs is regulated by various signals, including phosphorylation and interactions with other proteins, which can influence gene expression patterns.
4. Mutations or dysregulation of HATs can lead to various diseases, including cancer, as they play a role in controlling cell growth and differentiation.
5. HATs also have non-histone targets, meaning they can modify other proteins, influencing a variety of cellular processes beyond chromatin dynamics.

Review Questions

• How do histone acetyltransferases influence gene expression through their action on chromatin structure?
  • Histone acetyltransferases modify chromatin structure by adding acetyl groups to histones, which reduces the positive charge on lysine residues. This change decreases the interaction between histones and DNA, resulting in a more relaxed chromatin state. As a result, the DNA becomes more accessible to transcription machinery, promoting gene expression.
• Compare and contrast the roles of histone acetyltransferases and histone deacetylases in regulating chromatin dynamics.
  • Histone acetyltransferases (HATs) add acetyl groups to histones, which generally leads to a relaxed chromatin structure and increased gene expression. In contrast, histone deacetylases (HDACs) remove these acetyl groups, resulting in a more compact chromatin configuration that typically silences gene expression. Together, these enzymes maintain a dynamic balance in chromatin modification crucial for proper gene regulation.
• Evaluate the implications of dysregulated histone acetyltransferase activity on cellular functions and disease states.
  • Dysregulation of histone acetyltransferase activity can significantly disrupt normal cellular functions, leading to altered gene expression patterns. This can result in unchecked cell proliferation or differentiation, which are hallmark features of various diseases, particularly cancer. Understanding these mechanisms opens avenues for potential therapeutic interventions that target HATs or their pathways to restore normal gene regulation.

Related terms

Histone Deacetylase: An enzyme that removes acetyl groups from histones, leading to a more condensed chromatin structure and typically resulting in transcriptional repression.

Chromatin Remodeling: The dynamic modification of chromatin architecture to allow access to the genetic material for processes like transcription, replication, and repair.

Transcription Factors: Proteins that bind to specific DNA sequences to regulate the transcription of genetic information from DNA to messenger RNA.