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核受体超家族介导基因调控的分子机制 总被引：2，自引：0，他引：2
核受体超家族由甾体激素、甲状腺激素、维甲酸、维生素D等化学信号的受体及配体未明的多种孤儿受体组成,该家族成员的主要功能是作为配体激活的转录因子,调控代谢、发育、生殖相关基因的表达。核受体与启动子和增强子上的激素应答元件及其它DNA序列特异性激活因子结合,而激活或阻遏靶基因的转录。核受体调控基因转录需要募集称为辅调控因子的蛋白分子,这些蛋白分子与核受体一起装配成多组分的复合物,它们可提供相关的酶促活性和脚手架功能。通过与基础转录机器的相互作用和对染色质结构的可逆性共价修饰等作用,辅调控因子调控核受体对靶基因转录的激活或阻遏。许多辅调控因子本身受到多条细胞内信号转导途径的调控。 相似文献
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综述了5种集落刺激因子(CSF)、红细胞生成素(EPO)、5种白介素、干扰素、肿瘤坏死因子、白血病抑制因子、干细胞抑制因子、2种 CSF 受体 (R)、EPOR 和两种白介素 R 等转录调控分子机制的研究进展. 相似文献
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辅调节因子在核受体基因表达调控中的作用 总被引：1，自引：0，他引：1
核受体 ( nuclear receptor)在增强或抑制基因转录时 ,需借助于诸多辅调节因子的协同作用 ,使调节更为精细、有效及特异 .辅调节因子 ( coregulator)可区分为辅激活因子 ( coactivator)和辅抑制因子 ( corepressor)两大类 ,均具有多种功能各异的蛋白质因子 ,分别汇聚于核受体上构成不同复合体 .它们的主要作用机理是 :( 1 )促使核小体中的组蛋白乙酰基化 ,导致与 DNA的结合松散 ;或脱乙酰基 ,而使组蛋白与 DNA的结合回复紧密状态 ,从而创造一个有利于转录或封闭转录的局部环境 ;( 2 )作用于通用转录因子及 RNA聚合酶 ,以激活转录或抑制转录 . 相似文献
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生物大分子（cargo）的核浆转运是由一些转运因子介导的,这些因子包括Kap-α、Kap-β、Ran-GTP及其调节蛋白等。本文阐述了在核浆转运过程中,各因子之间的相互作用及其结构变化,并提出cargo被释放入核的可能机制及一些有待深入研究的问题。 相似文献
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核受体是一类配体依赖的转录因子,它们之间有相似的结构,在进化为来源于同一前体,它们和基础转录因子有直接的联系,与配体结合后,作用于其目标基因的特定应答元件上,从而活化特定基因的转录,核受体介导的转录活化需要有辅活化子和辅阻遏子的参与,这些辅活化子和辅助遏子是有效的转录所必需的,它们能和核受体特异结合,并在核受体和基础转录因子之间发挥中介作用,目前发现普遍存在并在转录过程中具有重要作用的辅活化子有Ｃ 相似文献
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由胆固醇合成胆汁酸有两条途径。一条是经典途径或中性途径[1] ,也是合成胆汁酸最主要的途径 ,其限速反应为胆固醇 7α 羟化酶 (由Ｃｙｐ7ａ编码 )催化胆固醇羟化为 7α 羟胆固醇的反应。近几年发现另一条胆汁酸合成的酸性途径[2 ] ,这一途径开始于胆固醇转变为氧固醇 (ｏｘｙｓｔｅｒｏｌ) ,然后经氧固醇 7α 羟化酶 (由Ｃｙｐ7ｂ编码 )催化产生 7α 羟氧固醇化合物 ,再融入胆汁酸合成经典途径的下游步骤。由于胆固醇在体内有重要作用 ,有效调节胆固醇分解代谢以维持胆固醇水平的动态平衡十分重要。研究发现 ,胆汁酸以及合成过程中的中间产… 相似文献
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Nucleocytoplasmic transport of proteins 总被引：4，自引：0，他引：4
In eukaryotic cells, the movement of macromolecules between the nucleus and cytoplasm occurs through the nuclear pore complex (NPC)--a large protein complex spanning the nuclear envelope. The nuclear transport of proteins is usually mediated by a family of transport receptors known as karyopherins. Karyopherins bind to their cargoes via recognition of nuclear localization signal (NLS) for nuclear import or nuclear export signal (NES) for export to form a transport complex. Its transport through NPC is facilitated by transient interactions between the karyopherins and NPC components. The interactions of karyopherins with their cargoes are regulated by GTPase Ran. In the current review, we describe the NPC structure, NLS, and NES, as well as the model of classic Ran-dependent transport, with special emphasis on existing alternative mechanisms; we also propose a classification of the basic mechanisms of protein transport regulation. 相似文献
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Yagisawa H 《Journal of cellular biochemistry》2006,97(2):233-243
Phosphoinositides (PIs) and proteins involved in the PI signaling pathway are distributed in the nucleus as well as at the plasma membrane and in the cytoplasm, although their nuclear localization mechanisms have not been clarified in detail. Generally, proteins that shuttle between the cytoplasm and nucleus contain nuclear localization signal (NLS) and nuclear export signal (NES) sequences for nuclear import and export, respectively. They bind to specific carrier proteins of the importin/exportin family and are transported to and from the nucleus. Thus there is a steady state shuttling of the cargo molecules to and from the nucleus, and the shift in equilibrium determines their nuclear or cytoplasmic localization. Our previous studies have shown that phospholipase C (PLC)-delta1, regarded as having cytoplasmic- or plasma membrane-bound localization, accumulates in the nucleus when its NES sequence is disrupted. In addition, a cluster of positively charged residues on the surface of the catalytic barrel is important for nuclear import. In quiescent cells, the shuttling equilibrium seems to be shifted to the nuclear export of PLCdelta1. In this review, recent findings regarding the molecular machineries and mechanisms of the nucleocytoplasmic shuttling of PLCdelta1 will be discussed. It is important to know when and how they are regulated. A shift in the equilibrium in a certain stage of the cell cycle or by external stimuli is possible and resulting changes in the intra-nuclear environments (or architectures) may alter proliferation and differentiation patterns. Evidences support the idea that an increase in the levels of intracellular Ca2+ shifts the equilibrium to the nuclear import of PLCdelta1. A myriad of external stimuli have also been reported to change the nuclear PI metabolism following accelerated accumulation in the nucleus of other phospholipases such as phospholipase A2 and phospholipase D in addition to PLC isoforms such as PLCbeta1 and PLCgamma1. The consequence of the nuclear accumulation of PLC is also discussed. 相似文献
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Ed Hurt Stefan Hannus Birgit Schmelzl Denise Lau David Tollervey George Simos 《The Journal of cell biology》1999,144(3):389-401
To identify components involved in the nuclear export of ribosomes in yeast, we developed an in vivo assay exploiting a green fluorescent protein (GFP)-tagged version of ribosomal protein L25. After its import into the nucleolus, L25-GFP assembles with 60S ribosomal subunits that are subsequently exported into the cytoplasm. In wild-type cells, GFP-labeled ribosomes are only detected by fluorescence in the cytoplasm. However, thermosensitive rna1-1 (Ran-GAP), prp20-1 (Ran-GEF), and nucleoporin nup49 and nsp1 mutants are impaired in ribosomal export as revealed by nuclear accumulation of L25-GFP. Furthermore, overexpression of dominant-negative RanGTP (Gsp1-G21V) and the tRNA exportin Los1p inhibits ribosomal export. The pattern of subnuclear accumulation of L25-GFP observed in different mutants is not identical, suggesting that transport can be blocked at different steps. Thus, nuclear export of ribosomes requires the nuclear/cytoplasmic Ran-cycle and distinct nucleoporins. This assay can be used to identify soluble transport factors required for nuclear exit of ribosomes. 相似文献
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