[4] In addition p300 and CBP each contain a protein or histone acetyltransferase (PAT/HAT) domain and a bromodomain that binds acetylated lysines and a PHD finger motif with unknown function.

[9][10][11][12] Work done by Heintzman and colleagues[13] showed that 70% of the p300 binding occurs in open chromatin regions as seen by the association with DNase I hypersensitive sites.

The transcription factor CREB, which interacts with a DNA sequence called a cAMP response element (or CRE), is phosphorylated on a serine (Ser 133) in the KID domain.

These mutations result in the loss of one copy of the gene in each cell, which reduces the amount of CBP or p300 protein by half.

[16] CBP and p300 have also been found to be involved in multiple rare chromosomal translocations that are associated with acute myeloid leukemia.

[7] For example, researchers have found a translocation between chromosomes 8 and 22 (in the region containing the p300 gene) in several people with a cancer of blood cells called acute myeloid leukemia (AML).

Somatic mutations in the p300 gene have been found in a small number of solid tumors, including cancers of the colon and rectum, stomach, breast and pancreas.

Studies suggest that p300 mutations may also play a role in the development of some prostate cancers, and could help predict whether these tumors will increase in size or spread to other parts of the body.