CTPB is a selective activator of p300 HAT activity [1].

CREB binding protein (CBP) and E1A binding protein p300, also known as p300 are functionally related transcriptional co-activators (CoAs) and histone acetyltransferases (HATs). The p300/CBP is a global transcriptional coactivator, which plays a critical role in cell cycle control, differentiation, and apoptosis. Mutations in p300/CBP are associated with different human cancers and other human diseases [1][2].

CTPB, also known as N-(4-chloro-3-trifluoromethyl-phenyl)-2-ethoxy-6-pentadecyl-benza-mide, is an amide derivative that selectively activates p300 HAT activity. CTPB directly binds p300 [2]. CTPB exhibited an enhancement in the p300 HAT activity concentration-dependently with maximal activation at 275 μM. In the presence of p300, CTPB resulted in the gradual increase in the acetylation of both histones H3 and H4, peaking at 200 μM. Further increase in the concentration of CTPB reduced the HAT activity, could be due to an alteration in the reaction condition affecting the efficiency of the HAT. CTPB didn’t alter PCAF HAT or histone deacetylase activity [1].

References:
[1]. Balasubramanyam K, Swaminathan V, Ranganathan A, et al. Small molecule modulators of histone acetyltransferase p300. J Biol Chem. 2003 May 23;278(21):19134-40.
[2]. Devipriya B, Parameswari AR, Rajalakshmi G, et al. Exploring the binding affinities of p300 enzyme activators CTPB and CTB using docking method. Indian J Biochem Biophys. 2010 Dec;47(6):364-9.