蛋白质多肽氨基端乙酰化酶NatB介导底物特异性乙酰化反应的分子基础

文章简介蛋白质多肽氨基端乙酰化(N-terminal acetylation)发生在蛋白质或多肽的氨基端第一个氨基酸的(N端)α氨基上,是真核生物中一种最常见的蛋白质翻译后修饰方式。该修饰是由6类N端乙酰转移酶(NAT)来完成的(Nat A至Nat F),而每一种都只作用于其特异的蛋白国家自然科学基金委;;科技部的经费支

Signal-induced Brd4 release from chromatin is essential for its role transition from chromatin targeting to transcriptional regulation

Bromodomain-containing protein Brd4 is shown to persistently associate with chromosomes during mitosis for transmitting epigenetic memory across cell divisions. During interphase, Brd4 also plays a key role in regulating the transcription of signal-inducible genes by recruiting positive transcription elongation factor b (P-TEFb) to promoters. How the chromatin-bound Brd4 transits into a transcriptional regulation mode in response to stimulation, however, is largely unknown. Here, by analyzing the dynamics of Brd4 during ultraviolet or hexamethylene bisacetamide treatment, we show that the signal-induced release of chromatin-bound Brd4 is essential for its functional transition. In untreated cells, almost all Brd4 is observed in association with interphase chromatin. Upon treatment, Brd4 is released from chromatin, mostly due to signal-triggered deacetylation of nucleosomal histone H4 at acetylated-lysine 5/8 (H4K5ac/K8ac). Through selective association with the transcriptional active form of P-TEFb that has been liberated from the inactive multi-subunit complex in response to treatment, the released Brd4 mediates the recruitment of this active P-TEFb to promoter, which enhances transcription at the stage of elongation. Thus, through signal-induced release from chromatin and selective association with the active form of P-TEFb, the chromatin-bound Brd4 switches its role to mediate the recruitment of P-TEFb for regulating the transcriptional elongation of signal-inducible genes.National Natural Science Foundation of China[30930046, 30670408, 81070307]; Natural Science Foundation of Fujian[C0210005, 2010J01231]; Science Planning Program of Fujian Province[2009J1010, 2010J1008]; National Foundation for fostering talents of basic science[J1030626

p300/CBP and p300/CBP-associated Factor with Transcriptional Regulation

P300/CbP及其相关因子PCAf具有乙酰转移酶活性,能通过乙酰化组蛋白和非组蛋白的方式参与基因的转录调控.同时,它们也能介导多种转录因子.与大多数典型的转录辅激活子相同,它们能在转录因子和基本转录复合物之间起到桥梁作用.P300/CbP与细胞周期调控、细胞凋亡以及癌症的发生等过程之间有着直接的联系.本文概括介绍了P300/CbP与PCAf的基本特性,并简要介绍它们与其它蛋白之间的相互作用,特别是E1A的最新研究进展.p300/CBP and p300/CBP-associated factor(PCAF) exert an intrinsic histone acetyltransferase(HAT) activity.Histones and nonhistone proteins were acetylated to regulate transcriptions of specific sets of genes and interact with various transcription factors.Like the most classical transcriptional coactivators,p300/CBP and PCAF can also bridge the transcriptional factors to the basal transcriptional complex to maintain the appropriate levels of gene activities during various physiological processes,such as cell cycle,apoptosis and carcinogenesis.The review focuses on the basic characteristics of p300/CBP and PCAF,and the specific interactions with their protein partners in tumor progression,such as E1A,Rb and p53 are also discussed.国家自然科学基金专项基金项目(No.30840027)---

基于非局部低秩张量分解的三维医学图像超分辨率方法

本发明涉及基于非局部低秩张量分解的三维医学图像超分辨率方法。针对临床环境中受硬件条件、成像设备、传输效率等限制而无法直接得到高分辨率图像的问题，提出了一种单张三维医学图像的超分辨率方法。该方法采用非局部张量Tucker分解模型来充分利用图像的非局部相似先验，从而实现低分辨率图像的恢复。与现有基于凸优化的张量Tucker分解方法不同，该模型采用张量折凹范数逼近非局部低秩张量，避免了传统的凸优化方法带来的估计误差。同时，引入加权三维TV保持图像各个维度的局部平滑性。该方法在大脑和前列腺的磁共振成像(MRI)图像，腹部和牙科的计算机断层扫描(CT)图像等多种不同的三维医学图像上均得到了良好的超分辨率效果，验证了该方法的有效性和先进性

基于非凸低秩张量近似的图像超分辨率重建系统

本发明涉及基于非凸低秩张量近似的图像超分辨率重建系统。在医学领域，磁共振图像(MRI)、计算机断层扫描图像等诸多医学成像方面总受到医疗系统固有硬件、医学图像采集时间的制约而缺乏高分辨率(HR)的医学图像。针对医学图像超分(SR)问题，本发明利用耦合加权三维全变分(3DTV)的块张量非凸近似方法来提高医学图像的分辨率。首先，对输入的低分辨率图像进行块匹配操作形成4D块，然后采用非凸张量惩罚函数挖掘其中蕴含的低秩结构特性、非局部自相似性。采用加权的三维全变分正则项来挖掘医学图像数据的局部平滑特性。该方法解决了医学图像的分辨率增强、抑制噪声及图像细节恢复等问题并实验验证了在不同采样率、噪声水平下该算法的优越性和泛化性

Dimeric structure of p300/CBP associated factor

National Science Foundation of China [31170685, 90919036, 30840027]; Project 985 [0660ZK1022]; Program 111 [B06016]Background: p300/CBP associating factor (PCAF, also known as KAT2B for lysine acetyltransferase 2B) is a catalytic subunit of megadalton metazoan complex ATAC (Ada-Two-A containing complex) for acetylation of histones. However, relatively little is known about the regulation of the enzymatic activity of PCAF. Results: Here we present two dimeric structures of the PCAF acetyltransferase (HAT) domain. These dimerizations are mediated by either four-helical hydrophobic interactions or a beta-sheet extension. Our chemical cross-linking experiments in combined with site-directed mutagenesis demonstrated that the PCAF HAT domain mainly forms a dimer in solution through one of the observed interfaces. The results of maltose binding protein (MBP)-pulldown, co-immunoprecipitation and multiangle static light scattering experiments further indicated that PCAF dimeric state is detectable and may possibly exist in vivo. Conclusions: Taken together, our structural and biochemical studies indicate that PCAF appears to be a dimer in its functional ATAC complex

An efficient approach for site-directed mutagenesis using central overlapping primers

QuikChange is a popular method for site-directed mutagenesis in structural and functional studies of proteins and nucleic acids. However, the standard protocol is often inefficient in producing the desired mutations. Here we present a novel strategy for primer design, central overlapping primers (COP), which employs a pair of bipartite primers of different lengths, with the short primer complementary to the middle region of the long primer. The COP method is efficient and robust in generating approximately 90% mutation rate without supercompetent Escherichia coli cells or laborious screening for positive clones. (C) 2011 Elsevier Inc. All rights reserved.National Natural Science Foundation of China[30930046, 30670408, 30840027, 90919036]; Natural Science Foundation of Fujian[2008J0108]; Science Advancing Program of Fujian[2009J1010

Quikgene: A gene synthesis method integrated with ligation-free cloning

Gene synthesis is a convenient tool that is widely used to make genes for a variety of purposes. All current protocols essentially take inside-out approaches to assemble complete genes using DNA oligonucleotides or intermediate fragments. Here we present an efficient method that integrates gene synthesis and cloning into one step. Our method, which is evolved from QuikChange mutagenesis, can modify, extend, or even de nova synthesize relatively large genes. The genes are inserted directly into vectors without ligations or subcloning. We de novo synthesized a 600-bp gene through multiple steps of polymerase chain reaction (PCR) directly into a bacterial expression vector. This outside-in gene synthesis method is called Quikgene. Furthermore, we have defined an overlap region of a minimum of nine nucleotides in insertion primers that is sufficient enough to circularize PCR products for efficient transformation, allowing one to significantly reduce the lengths of primers. Taken together, our protocol greatly extends the current length limit for QuikChange insertion. More importantly, it combines gene synthesis and cloning into one step. It has potential applications for high-throughput structural genomics. (C) 2011 Elsevier Inc. All rights reserved.National Natural Science Foundation of China[30840027, 90919036]; Project 985; Fujian Science Advancing Program[2009J1010]; Project 111[B06016