Final answer:
Histone DeAcetyltransferases (HDACs) are responsible for the deacetylation of histones, leading to a more condensed chromatin structure and decreased accessibility of DNA for transcription.
Step-by-step explanation:
What do Histone DeAcetyltransferases (HDACs) do? The answer is C) Deacetylation of histones. HDACs are enzymes that remove acetyl groups from histone proteins. The process of deacetylation generally causes the chromatin structure to become more condensed, making the DNA less accessible for transcription. This action is in contrast to histone acetylation, which is associated with loosening of the chromatin structure and promotion of transcription by allowing greater access to the DNA. Thus, HDACs play an essential role in the regulation of gene expression by modifying chromatin structure and subsequently influencing transcriptional activity.