In an experiment in my laboratory, I used siRNA to decrease the amounts of a HDAC that removes the H3K9ac mark. What observations would I expect in terms of changes in gene expression?
HDAC is histone deacetylase enzyme. This enzyme is responsible for the removal of acetyl group from the amino acids of histone proteins.
Acetylation is the type of epigenetic regulation in which acetyl group is added to a specific amino acid of histone proteins. In general, acetylation tend to loosen the packing of chromatin and therefore increases gene expression. The loose packing of chromatin is responsible for increasing the accessibility of RNA polymerase towards the gene and therefore the rate of transcription increases.
Acetyl groups are added to histone protein by enzymes called as acetyltransferases are removed by deacetylases.
In the given question, we have decreased the amount of deacetylase. It means histone proteins will now remain acetylated. And when the proteins are acetylated, the rate of gene expression is more. So we can predict an increase in the rate of transcription.
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