Conditional knockout mice reveal distinct functions for the global transcriptional coactivators CBP and p300 in...

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• CREB-binding protein (CBP) and p300 are global transcriptional coactivators with extensive protein interactions.
• Homozygous null mutations in CBP or p300 cause embryonic lethality, limiting studies in adult tissues.
• The specific roles of CBP and p300 in adult cell lineages remain largely uncertain.

Purpose of the Study:

• To investigate the functions of CBP and p300 in T-cell development and immune responses in adult mice.
• To generate and utilize conditional knockout models for temporal and tissue-specific inactivation of CBP and p300.
• To elucidate the redundant and unique contributions of CBP and p300 in T cells and macrophages.

Main Methods:

• Generation of a conditional p300 knockout allele (p300flox) using Cre/LoxP technology.
• Crossbreeding p300flox mice with CBP conditional knockout mice (CBPflox) and an Lck-Cre transgene.
• Analysis of T-cell development in the thymus and periphery, and gene expression in response to stimulation in T cells and macrophages.

Main Results:

• Loss of either CBP or p300 reduced CD4+ CD8+ double-positive thymocytes.
• CBP deficiency, but not p300 deficiency, led to an increase in CD8+ single-positive thymocytes.
• T cells lacking both CBP and p300 showed impaired development and were rare in the periphery.
• Tumor necrosis factor alpha gene expression was reduced in T cells lacking CBP or p300.
• Signal-responsive gene expression in macrophages was largely unaffected by CBP or p300 deficiency.

Conclusions:

• CBP and p300 exhibit significant functional redundancy in T cells and macrophages.
• Each coactivator possesses unique roles in thymocyte development.
• Conditional knockout models are crucial for studying the functions of essential genes in adult organisms.