Summary
Acetylation, methylation and phosphorylation of histone tails alter chromatin openness and gene activity.
In depth
Histone acetylation neutralises lysine charge, loosens chromatin and activates genes; HDACs remove acetyls. Methylation can activate (H3K4me3) or repress (H3K27me3, H3K9me3). Readers, writers and erasers form the histone code.
HDAC inhibitors are used as cancer drugs.
The histone code idea suggests that combinations of marks have meaning, read by proteins with bromodomains (acetyl-lysine) or chromodomains (methyl-lysine). Writers add the marks (HATs, methyltransferases), readers recognise them, and erasers remove them (HDACs, demethylases). Phosphorylation of H3 serine 10 accompanies mitosis, and ubiquitination of H2A marks damage and repression.
Drugs that alter histone marks include HDAC inhibitors such as vorinostat for lymphoma, and EZH2 inhibitors for some cancers. Histone variants (H2A.Z, H3.3, CENP-A at centromeres) add more regulation.
Example: H3K27me3 laid down by Polycomb complexes keeps developmental genes silent in cells where they should not be active.
Frequently asked questions
What is Histone Modification?
Acetylation, methylation and phosphorylation of histone tails alter chromatin openness and gene activity.
Which area of biology covers Histone Modification, and how advanced is it?
Histone Modification is one of the 52 topics in Molecular Biology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Transcription Factors, DNA Methylation, Gene Expression.
Can you give an example of Histone Modification?
H3K9me3 marks constitutive heterochromatin.
What should I learn before Histone Modification?
Work through the Beginner topics in Molecular Biology first, such as Central Dogma, DNA Replication, Base Pairing, then return to Histone Modification. Intermediate topics assume the Beginner vocabulary.
What topics are related to Histone Modification?
The closest topics to Histone Modification are Transcription Factors, DNA Methylation, Gene Expression, DNA Packaging. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Histone Modification?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Histone Modification. To practise the whole of Molecular Biology, use the Molecular Biology quiz.
How is Histone Modification different from Transcription Factors?
Histone Modification: Acetylation, methylation and phosphorylation of histone tails alter chromatin openness and gene activity. Transcription Factors: Proteins that bind specific DNA sequences to turn genes on or off. Read both side by side and note what each one explains.
How should I study Histone Modification step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Transcription Factors and explain the difference aloud. Finally, take the Molecular Biology quiz and come back to this page for any question you miss.