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211.
Translation initiation is a critical step in protein synthesis. Previously, two major mechanisms of initiation were considered
as essential: prokaryotic, based on SD interaction; and eukaryotic, requiring cap structure and ribosomal scanning. Although
discovered decades ago, cap-independent translation has recently been acknowledged as a widely spread mechanism in viruses,
which may take place in some cellular mRNA translations. Moreover, it has become evident that translation can be initiated
on the leaderless mRNA in all three domains of life. New findings demonstrate that other distinguishable types of initiation
exist, including SD-independent in Bacteria and Archaea, and various modifications of 5′ end-dependent and internal initiation
mechanisms in Eukarya. Since translation initiation has developed through the loss, acquisition, and modification of functional
elements, all of which have been elevated by competition with viral translation in a large number of organisms of different
complexity, more variation in initiation mechanisms can be anticipated. 相似文献
212.
Montuori N Bifulco K Carriero MV La Penna C Visconte V Alfano D Pesapane A Rossi FW Salzano S Rossi G Ragno P 《Cellular and molecular life sciences : CMLS》2011,68(14):2453-2467
The receptor (CXCR4) for the stromal-derived factor-1 (SDF1) and the urokinase-receptor (uPAR) are up-regulated in various tumors. We show that CXCR4-transfected cells migrate toward SDF1 on collagen (CG) and do not on vitronectin (VN). Co-expression of cell-surface uPAR, which is a VN receptor, impairs SDF1-induced migration on CG and allows migration on VN. Blocking fMLP receptors (fMLP-R), alpha-v integrins or the uPAR region capable to interact with fMLP-Rs, impairs migration of uPAR/CXCR4-transfected cells on VN and restores their migration on CG. uPAR co-expression also reduces the adherence of CXCR4-expressing cells to various components of the extracellular matrix (ECM) and influences the partitioning of beta1 and alpha-v integrins to membrane lipid-rafts, affecting ECM-dependent signaling. uPAR interference in CXCR4 activity has been confirmed in cells from prostate carcinoma. Our results demonstrate that uPAR expression regulates the adhesive and migratory ability of CXCR4-expressing cells through a mechanism involving fMLP receptors and alpha-v integrins. 相似文献
213.
Lubka-Pathak M Shah AA Gallozzi M Müller M Zimmermann U Löwenheim H Pfister M Knipper M Blin N Schimmang T 《Cellular and molecular life sciences : CMLS》2011,68(16):2739-2749
Introduction
Tff3 peptide exerts important functions in cytoprotection and restitution of the gastrointestinal (GI) tract epithelia. Moreover, its presence in the rodent inner ear and involvement in the hearing process was demonstrated recently. However, its role in the auditory system still remains elusive. Our previous results showed a deterioration of hearing with age in Tff3-deficient animals.Results
Present detailed analysis of auditory brain stem response (ABR) measurements and immunohistochemical study of selected functional proteins indicated a normal function and phenotype of the cochlea in Tff3 mutants. However, a microarray-based screening of tissue derived from the auditory central nervous system revealed an alteration of securin (Pttg1) and serpina3n expression between wild-type and Tff3 knock-out animals. This was confirmed by qRT-PCR, immunostaining and western blots.Conclusions
We found highly down-regulated Pttg1 and up-regulated serpina3n expression as a consequence of genetically deleting Tff3 in mice, indicating a potential role of these factors during the development of presbyacusis. 相似文献214.
Effectiveness of immune surveillance of intracellular viruses and bacteria depends upon a functioning antigen presentation
pathway that allows infected cells to reveal the presence of an intracellular pathogen. The antigen presentation pathway uses
virtually all endogenous polypeptides as a source to produce antigenic peptides that are eventually chaperoned to the cell
surface by MHC class I molecules. Intriguingly, MHC I molecules present peptides encoded not only in the primary open reading
frames but also those encoded in alternate reading frames. Here, we review recent studies on the generation of cryptic pMHC
I. We focus on the immunological significance of cryptic pMHC I, and the novel translational mechanisms that allow production
of these antigenic peptides from unconventional sources. 相似文献
215.
对于终身主题模型而言,先验知识的正确性对后续的建模任务起到了至关重要的作用.因此,提出了一种基于语义相似度改进的少样本终身主题模型SS-AMC(Semantic Similarity-AMC),利用BERT获取共现词对的词向量,计算其语义相似度,通过设置相似度阈值进而优化知识库中的先验知识,以提升少样本终身主题模型的性能.在中英文数据集上的实验结果表明,SS-AMC模型的主题一致性较基线模型有了明显的提升. 相似文献
216.
随着互联网的快速发展及各种数字化设备的普及,现代数字社会中的图像信息的数量在迅猛增长,图像信息的检索技术的研究得到了越来越多的关注.本文介绍了基于文本的图像检索技术与基于内容的图像检索技术,比较研究了这两种技术的不同的特点,指出综合运用TBIR和CBIR共同检索Web图像. 相似文献
217.
218.
对空间变量应用中心差分格式离散,时间变量采用指数函数的Pade’[2/1]逼近,构造了对流扩散方程的精度为O(τ3+h2)的绝对稳定的隐式差分格式,并对其稳定性进行了讨论,将数值实验结果与Crank-Nicholson格式进行比较,验证了文中方法的有效性. 相似文献
219.
220.