Final Answer:
SMRT does NOT have HAT activity. Option C is correct.
Step-by-step explanation:
The correct answer is C) SMRT. HAT (Histone Acetyltransferase) activity is associated with enzymes that catalyze the acetylation of histones, a process involved in the regulation of gene expression. p300, CPB, and PCAF are all examples of proteins with HAT activity. The p160 family of coactivators, represented by option E, also possesses HAT activity.
On the other hand, SMRT (Silencing Mediator of Retinoid and Thyroid hormone receptors), represented by option C, does not have HAT activity. SMRT is a corepressor that functions by recruiting histone deacetylases (HDACs) to deacetylate histones, leading to gene repression. Unlike HATs, which add acetyl groups to histones, HDACs remove these acetyl groups. Therefore, SMRT plays a role in histone deacetylation rather than acetylation.
In summary, while options A, B, D, and E exhibit HAT activity, option C (SMRT) does not possess this function. Understanding the distinct activities of these proteins is crucial in unraveling the complexities of gene regulation and chromatin remodeling.