Increased affinity of c-Myb for CREB-binding protein (CBP) after CBP-induced acetylation
Increased affinity of c-Myb for CREB-binding protein (CBP) after CBP-induced acetylation
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DOI：
10.1074/jbc.m006896200
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发表时间：
2001-02-02
影响因子：
4.8
通讯作者：
Ishii, S
中科院分区：
文献类型：
--
作者：
Sano, Y;Ishii, S
c-myb原癌基因产物（c-myb）是一种序列特异性dna结合蛋白，起转录激活剂的作用。转录辅激活因子creb结合蛋白（CBP）通过其KM结构域结合到c-Myb的激活结构域，介导c-Myb依赖的转录激活，CBP具有内在的组蛋白乙酰转移酶活性，不仅可以使组蛋白乙酰化，还可以使某些转录因子如GATA1和p53乙酰化。本研究表明，CBP的C/H2结构域对乙酰转移酶活性至关重要，它也直接与C - myb的负调控结构域（NRD）相互作用。与这一观察结果一致，CBP在体外使c-Myb在NRD的Lys（438）和Lys（441）乙酰化。此外，CBP在体内不仅在本研究中发现的位点上使c-Myb乙酰化，而且在最近报道的p300诱导的乙酰化位点上也使其乙酰化。赖氨酸在所有这些位点被精氨酸取代，显著降低了c-Myb的反式激活能力。对c-Myb乙酰化位点突变体的转录激活分析结果表明，这五个位点上的c-Myb乙酰化协同增强了c-Myb活性。这些乙酰化位点的突变降低了c-Myb和CBP之间相互作用的强度。因此，CBP对c-Myb的乙酰化通过增强c-Myb与CBP的关联而增加了c-Myb的反式激活能力。这些结果证明了一种新的调节c-Myb活性的分子机制。
The c-myb proto-oncogene product (c-Myb) is a sequence-specific DNA-binding protein that functions as a transcriptional activator. The transcriptional coactivator CREB-binding protein (CBP) binds via its KM domain to the activation domain of c-Myb and mediates c-Myb-dependent transcriptional activation, CBP possesses intrinsic histone acetyltransferase activity, and can acetylate not only histones but also certain transcriptional factors such as GATA1 and p53. Here we demonstrate that the C/H2 domain of CBP, which is critical for the acetyltransferase activity, also directly interacts with the negative regulatory domain (NRD) of c-Myb. Consistent with this observation, CBP acetylated c-Myb in vitro at Lys(438) and Lys(441) within the NRD. In addition, CBP acetylated c-Myb in vivo not only at the sites found in this study but also at the p300-induced acetylation sites reported recently. Replacement of lysine by arginine at all of these sites dramatically decreased the trans-activating capacity of c-Myb. The results of transcriptional activation assays with c-Myb acetylation site mutants suggested that acetylation of c-Myb at each of these five sites synergistically enhances c-Myb activity. Mutations of these acetylation sites reduced the strength of the interaction between c-Myb and CBP. Thus, acetylation of c-Myb by CBP increases the trans-activating capacity of c-Myb by enhancing its association with CBP. These results demonstrate a novel molecular mechanism of regulation of c-Myb activity.