Perturbing the ubiquitin pathway reveals how mitosis is hijacked to denucleate and regulate cell proliferation and differentiation in vivo.
Perturbing the ubiquitin pathway reveals how mitosis is hijacked to denucleate and regulate cell proliferation and differentiation in vivo.
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DOI：
10.1371/journal.pone.0013331
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发表时间：
2010-10-20
期刊：
影响因子：
3.7
通讯作者：
Taylor A
中科院分区：
文献类型：
--
作者：
Caceres A;Shang F;Wawrousek E;Liu Q;Avidan O;Cvekl A;Yang Y;Haririnia A;Storaska A;Fushman D;Kuszak J;Dudek E;Smith D;Taylor A
眼透镜提供了一个独特的机会，探索特定分子在细胞增殖，分化和发育中的作用，因为细胞在整个生命过程中保持原位，并且像红细胞和角质形成细胞一样，它们经历最极端的分化，包括细胞核的去除和蛋白质合成的停止。泛素化控制着许多关键的细胞过程，其中大多数需要泛素（Ub）上的特异性赖氨酸。在7种赖氨酸（K）中，对K6修饰的影响知之甚少。我们用色氨酸（W）代替K6，因为K6是最容易修饰的K，W是与生物素结构最相似的残基。K6 W-Ub的主链与Wt-Ub的主链不可区分。K6 W-Ub可有效结合和解结合，但结合物不会通过泛素蛋白酶体途径（UPP）降解。透镜和透镜细胞中K6 W-泛素的表达导致细胞内聚集体的积累，并且还减缓细胞增殖和分化程序，包括透镜特异性蛋白的表达、上皮细胞分化成纤维、实现适当的纤维细胞形态和去除细胞核。后者对透明度至关重要，但细胞核被去除的机制仍然是一个古老的谜。这也通过表达K6 W-Ub来解决。p27 kip是一种UPP底物，在表达K6 W-Ub的晶状体中积累。这就排除了核纤层蛋白被有丝分裂激酶磷酸化的可能性，这是核膜解体的先决条件。因此，细胞核保持完整，DNAseIIβ既不进入细胞核，也不降解DNA。这些结果无法使用不能针对特定组织的化学蛋白酶体抑制剂获得。K6 W-Ub为研究UPP的功能提供了一种新的遗传手段，因为它可以靶向特定的细胞和组织。执行透镜分化的大多数阶段，特别是去除细胞核，需要功能齐全的UPP。在没有功能性UPP的情况下，形成小的聚集倾向性白内障晶状体。
The eye lens presents a unique opportunity to explore roles for specific molecules in cell proliferation, differentiation and development because cells remain in place throughout life and, like red blood cells and keratinocytes, they go through the most extreme differentiation, including removal of nuclei and cessation of protein synthesis. Ubiquitination controls many critical cellular processes, most of which require specific lysines on ubiquitin (Ub). Of the 7 lysines (K) least is known about effects of modification of K6. We replaced K6 with tryptophan (W) because K6 is the most readily modified K and W is the most structurally similar residue to biotin. The backbone of K6W-Ub is indistinguishable from that of Wt-Ub. K6W-Ub is effectively conjugated and deconjugated but the conjugates are not degraded via the ubiquitin proteasome pathways (UPP). Expression of K6W-ubiquitin in the lens and lens cells results in accumulation of intracellular aggregates and also slows cell proliferation and the differentiation program, including expression of lens specific proteins, differentiation of epithelial cells into fibers, achieving proper fiber cell morphology, and removal of nuclei. The latter is critical for transparency, but the mechanism by which cell nuclei are removed has remained an age old enigma. This was also solved by expressing K6W-Ub. p27kip, a UPP substrate accumulates in lenses which express K6W-Ub. This precludes phosphorylation of nuclear lamin by the mitotic kinase, a prerequisite for disassembly of the nuclear membrane. Thus the nucleus remains intact and DNAseIIβ neither gains entry to the nucleus nor degrades the DNA. These results could not be obtained using chemical proteasome inhibitors that cannot be directed to specific tissues. K6W-Ub provides a novel, genetic means to study functions of the UPP because it can be targeted to specific cells and tissues. A fully functional UPP is required to execute most stages of lens differentiation, specifically removal of cell nuclei. In the absence of a functional UPP, small aggregate prone, cataractous lenses are formed.
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影响因子：
2.3
作者：
Groothuis TA;Dantuma NP;Neefjes J;Salomons FA
通讯作者：
Salomons FA
影响因子：
11.8
作者：
Nakayama, K;Nagahama, H;Nakayama, KI
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Nakayama, KI
影响因子：
4.8
作者：
JOHNSON, ES;MA, PCM;VARSHAVSKY, A
通讯作者：
VARSHAVSKY, A
影响因子：
16
作者：
Korolchuk, Viktor I.;Mansilla, Alicia;Menzies, Fiona M.;Rubinsztein, David C.
通讯作者：
Rubinsztein, David C.
影响因子：
5.3
作者：
Bedford, Lynn;Hay, David;Mayer, R. John
通讯作者：
Mayer, R. John