Histone acetyltransferases

Definition

Histone acetyltransferases (HATs) are enzymes that add acetyl groups to the amino-terminal tails of histone proteins, a process that plays a crucial role in the regulation of gene expression and chromatin structure. By acetylating histones, HATs promote a more relaxed chromatin configuration, facilitating access to DNA for transcription and thereby influencing cellular differentiation. The activity of HATs is vital for the activation of genes required during various developmental processes.

5 Must Know Facts For Your Next Test

1. HATs are crucial in modifying histones at specific lysine residues, which alters their interaction with DNA and other proteins involved in transcription.
2. The activity of HATs is often associated with active transcription and is linked to cellular differentiation processes, helping cells adopt specific fates.
3. HATs can be classified into two main types: Type A HATs, which are primarily nuclear, and Type B HATs, which are associated with cytoplasmic functions.
4. Various coactivators often work alongside HATs to recruit them to specific gene promoters, enhancing transcriptional activity.
5. Disruption in HAT function can lead to misregulation of gene expression, contributing to developmental disorders and diseases like cancer.

Review Questions

• How do histone acetyltransferases influence gene expression during cellular differentiation?
  • Histone acetyltransferases influence gene expression by adding acetyl groups to histones, which relaxes the chromatin structure. This relaxed state allows transcription factors and other regulatory proteins to access DNA more easily. During cellular differentiation, the activation of specific genes is essential, and HATs play a key role in facilitating this process by modifying histones at target gene promoters.
• Compare the roles of histone acetyltransferases and deacetylases in regulating chromatin structure and gene expression.
  • Histone acetyltransferases (HATs) add acetyl groups to histones, leading to a more open chromatin structure that promotes gene activation. In contrast, deacetylases remove these acetyl groups, tightening chromatin structure and generally repressing gene expression. The balance between the activities of HATs and deacetylases is crucial for maintaining proper regulation of gene expression, especially during processes like cellular differentiation.
• Evaluate the implications of dysregulated histone acetyltransferase activity on cellular function and disease.
  • Dysregulated activity of histone acetyltransferases can have profound implications on cellular function, as it may lead to inappropriate activation or silencing of genes. This misregulation can contribute to developmental disorders, as cells may not differentiate correctly into their intended lineages. Moreover, altered HAT activity is linked to various diseases, including cancer, where abnormal gene expression patterns drive tumorigenesis. Understanding these implications helps illuminate potential therapeutic targets for treatment.

Related terms

Histones:

Proteins that package and order DNA into structural units called nucleosomes, which help regulate gene expression.

Deacetylases: Enzymes that remove acetyl groups from histones, leading to tighter chromatin structure and typically repressing gene expression.

Epigenetics:

The study of heritable changes in gene expression that do not involve changes to the underlying DNA sequence, often influenced by modifications like acetylation.