Mouse models

CBP and p300 are critical for normal embryonic development, as mice completely lacking either CBP or p300 protein, die at an early embryonic stage. In addition, mice which lack one functional copy (allele) of both the CBP and p300 genes (i.e. are heterozygous for both CBP and p300) and thus have half of the normal amount of both CBP and p300, also die early in embryogenesis. 

• Yao TP, Oh SP, Fuchs M, Zhou ND, Ch’ng LE, Newsome D, Bronson RT, Li E, Livingston DM, Eckner R (May 1998). “Gene dosage-dependent embryonic development and proliferation defects in mice lacking the transcriptional integrator p300”. Cell. 93 (3): 361–72. doi:10.1016/S0092-8674(00)81165-4. PMID 9590171. S2CID 620460.
• Tanaka Y, Naruse I, Hongo T, Xu M, Nakahata T, Maekawa T, Ishii S (Jul 2000). “Extensive brain hemorrhage and embryonic lethality in a mouse null mutant of CREB-binding protein”. Mechanisms of Development. 95 (1–2): 133–45. doi:10.1016/S0925-4773(00)00360-9. PMID 10906457. S2CID 7141012.

This indicates that the total amount of CBP and p300 protein is critical for embryo development. Data suggest that some cell types can tolerate loss of CBP or p300 better than the whole organism can. Mouse B cells or T cells lacking either CBP and p300 protein develop fairly normally, but B or T cells that lack both CBP and p300 fail to develop in vivo.

• Xu W, Fukuyama T, Ney PA, Wang D, Rehg J, Boyd K, van Deursen JM, Brindle PK (Jun 2006). “Global transcriptional coactivators CREB-binding protein and p300 are highly essential collectively but not individually in peripheral B cells”. Blood. 107 (11): 4407–16. doi:10.1182/blood-2005-08-3263. PMC 1895794. PMID 16424387.
• Kasper LH, Fukuyama T, Biesen MA, Boussouar F, Tong C, de Pauw A, Murray PJ, van Deursen JM, Brindle PK (Feb 2006). “Conditional knockout mice reveal distinct functions for the global transcriptional coactivators CBP and p300 in T-cell development”. Molecular and Cellular Biology. 26 (3): 789–809. doi:10.1128/MCB.26.3.789-809.2006. PMC 1347027. PMID 16428436.

Together, the data indicate that, while individual cell types require different amounts of CBP and p300 to develop or survive and some cell types are more tolerant of loss of CBP or p300 than the whole organism, it appears that many, if not all cell types may require at least some p300 or CBP to develop.