Herrera J E, Schiltz R L, Bustin M
Protein Section, Laboratory of Metabolism, Division of Basic Science, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Biol Chem. 2000 Apr 28;275(17):12994-9. doi: 10.1074/jbc.275.17.12994.
P300/CBP-associated factor (PCAF) is a transcriptional coactivator with intrinsic histone acetylase activity. Reversible acetylation of the core histone tails in chromatin has been linked to transcriptional regulation. Here we investigate the mechanism whereby PCAF acetylates its target in chromatin. We demonstrate that recombinant PACF preferentially acetylates the H3 tail in oligonucleosomes, as compared with nucleosome core particles. The rate of acetylation is directly related to the length of the oligonucleosomal substrate. Using a trypsin accessibility assay, we demonstrate that the rate of acetylation is also related to the accessibility of the H3 tail in uncondensed oligonucleosomes. We suggest that PCAF, and perhaps other histone acetyltransferases, acetylate chromatin templates more efficiently than core particle subunits and that this preference arises from an increased accessibility of the H3 tail in either condensed or uncondensed oligonucleosomes. Acetylation of the H3 tails by the native PCAF complex is not affected by the length of the oligonucleosomal substrate. Our results suggest that the accessibility of the H3 tail in chromatin is a major factor affecting their rate of acetylation and that component(s) in the native PCAF complex function to modify the organization of these tails in chromatin thereby enhancing their accessibility to PCAF.
P300/CBP相关因子（PCAF）是一种具有内在组蛋白乙酰转移酶活性的转录共激活因子。染色质中核心组蛋白尾巴的可逆乙酰化与转录调控有关。在此，我们研究PCAF在染色质中使其靶标乙酰化的机制。我们证明，与核小体核心颗粒相比，重组PCAF优先使寡核小体中的H3尾巴乙酰化。乙酰化速率与寡核小体底物的长度直接相关。使用胰蛋白酶可及性分析，我们证明乙酰化速率也与未浓缩寡核小体中H3尾巴的可及性有关。我们认为，PCAF以及其他组蛋白乙酰转移酶可能比核心颗粒亚基更有效地使染色质模板乙酰化，这种偏好源于浓缩或未浓缩寡核小体中H3尾巴可及性的增加。天然PCAF复合物对H3尾巴的乙酰化不受寡核小体底物长度的影响。我们的结果表明，染色质中H3尾巴的可及性是影响其乙酰化速率的主要因素，并且天然PCAF复合物中的成分起到改变这些尾巴在染色质中的组织方式的作用，从而增强它们对PCAF的可及性。
