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81.
Jacqueline C. Merrill Tiffany A. Melhuish Michael H. Kagey Shen-Hsi Yang Andrew D. Sharrocks David Wotton 《PloS one》2010,5(1)
Background
Modification of proteins by the small ubiquitin like modifier (SUMO) is an essential process in mammalian cells. SUMO is covalently attached to lysines in target proteins via an enzymatic cascade which consists of E1 and E2, SUMO activating and conjugating enzymes. There is also a variable requirement for non-enzymatic E3 adapter like proteins, which can increase the efficiency and specificity of the sumoylation process. In addition to covalent attachment of SUMO to target proteins, specific non-covalent SUMO interaction motifs (SIMs) that are generally short hydrophobic peptide motifs have been identified.Methodology/Principal Findings
Intriguingly, consensus SIMs are present in most SUMO E3s, including the polycomb protein, Pc2/Cbx4. However, a role for SIMs in SUMO E3 activity remains to be shown. We show that Pc2 contains two functional SIMs, both of which contribute to full E3 activity in mammalian cells, and are also required for sumoylation of Pc2 itself. Pc2 forms distinct sub-nuclear foci, termed polycomb bodies, and can recruit partner proteins, such as the corepressor CtBP. We demonstrate that mutation of the SIMs in Pc2 prevents Pc2-dependent CtBP sumoylation, and decreases enrichment of SUMO1 and SUMO2 at polycomb foci. Furthermore, mutational analysis of both SUMO1 and SUMO2 reveals that the SIM-interacting residues of both SUMO isoforms are required for Pc2-mediated sumoylation and localization to polycomb foci.Conclusions/Significance
This work provides the first clear evidence for a role for SIMs in SUMO E3 activity. 相似文献82.
Effects of environmental conditions on the fixation and transfer of nitrogen from alfalfa to associated timothy 总被引:3,自引:0,他引:3
Nitrogen fixation (NF) by alfalfa and nitrogen transfer (NT) from alfalfa to associated timothy was studied under different
environmental conditions in controlled growth chambers, using the15N dilution technique. Evidence was obtained of NT from alfalfa to the associated timothy. Conditions that favored NF by alfalfa
resulted in an increase in its NT. Of 3 different temperature regimes (25/20, 16/14, and 12/9°C day/night), 16–25/14–20°C
was the best range for NF by alfalfa and resulted in the greatest NT. High light intensity (550 uE.m−2.sec−1) and long days (16–20 h) also caused increased NF by alfalfa and benefitting timothy more than in a regime of low light intensity
(by shading 50% or 75%) or short days (12/12 or 16/8 h day/night). When the inoculated (Rhizobium meliloti) root systems of plants were kept free from other microorganisms (axenic condition) to minimize possible decomposition of
dead tissues, lower NT from alfalfa was observed, especially at later cuts, compared to non-axenic plants. This suggests that
both direct excretion and decomposition of dead alfalfa tissues are sources of N benefit from alfalfa to associated timothy.
Contribution no 1065 of the Plant Research Centre. 相似文献
83.
The time-dependence of Mn accumulation was confirmed in potato foliage (Solanum tuberosum. L.cv. Norland) grown in solution culture. Older leaves grown at 0.61 mM Mn had substantially higher Mn concentrations than younger leaves and stem samples. Levels of Mn in older leaves increased steadily from 4000 µg g–1 at one week to 8–10,000 µg g–1 at 6 weeks, but were relatively constant in the emerging leaves. Even foliage grown at low Mn levels (0.01 mM Mn) had 4 fold gradients in Mn concentration from younger (40 µg g–1) to older leaves (180 µg g–1).At 0.61 mM Mn, concentrations of 3–4000 µg g–1 in the youngest fully-developed leaves did not bring about any decline in yield, and levels of up to 5000 µg g–1 occurred in individual potato leaves before Mn toxicity symptoms were observed. Potato foliage grown at the high Mn had similar leaf numbers, but showed an increased stem length and smaller leaves than foliage grown at 0.01 mM Mn. In particular, the leaf area of the middle and lower leaf fractions were affected by the high Mn level.The ability of rapidly growing plants to withstand high concentrations of Mn is discussed in relation to the pattern of dry matter and Mn accumulation shown by potato foliage. 相似文献
84.
黄地老虎核型多角体病毒的一些特性 总被引:1,自引:1,他引:0
黄地老虎核型多角体病毒(Agrotis segetum Nulear Polyhedrosis Virus简称AsNPV)的国内分离株(AsNPVC),多角体呈六边形,大小1.7—2.6μm,为多粒包埋类型.每个病毒束内有2—7个核衣壳,大小约52nm×308nm.感染烟青虫(Heliothis assttlta)后分离到的多角体(As-HaNPV)其形状不规则,大小0.7—2.6μm,亦为多粒包埋类型.核衣壳2—6个不等,大小约40nm×300nm.EcoR1和HindⅢ限制性内切酶电泳图谱分析表明,AsNPVCDNA和As-HaNPV DNA的EcoRI、HindIII酶切图谱一致,两者与HaNPV DNA的EcoRI,HindⅢ酶切图谱存在明显差异,AsNPVC DNA的EcoRI酶切图谱共有15个片段,分子量在12.74×106—1.18×106道尔顿之间,总分子量约88.6×106道尔顿,相当于134.25kbp.HaNPV DNA的EcoRI酶切图谱共有19个片段,分子量在13.89×106—1.10×106道尔顿之间,总分子量约93.86×106道尔顿,相当于142.25kbp.AsNPV对黄地老虎2龄和4龄幼虫以及对烟青虫4龄幼虫的LD50分别为:1.4×105pIB、7.4×104PIB和2.61×104PIB. 相似文献
85.
Regulation of Na,K-pump-mediated transport by prolactin in cultured human prostate epithelial cells.
M J Duran M Chosseler TA Pressley 《Cellular and molecular biology, including cyto-enzymology》2004,50(7):809-814
The prostate gland is unique in its ability to secrete large amounts of zinc and citrate, suggesting that it employs unusual transport mechanisms. Intracellular ionic homeostasis in prostate is likely to be mediated by the Na,K-pump, yet there have been few studies of its regulation in this tissue. Accordingly, we explored the expression of the Na,K-pump in PC3 cells, an established cell line of human prostate epithelial cells. Total RNA from confluent monolayers of PC3 cells was isolated, reverse transcribed, and the resulting complementary DNA was amplified by polymerase chain reaction using primers specific for each of the pump's constituent subunits. The amplification revealed a complex pattern of Na,K-pump expression, with detection of mRNAs encoding the alpha1-, alpha3-, alpha4-, betal-, beta2- and beta3-isoforms. We next examined the effect on pump activity of prolactin, an important mediator of cell proliferation in prostate cancer. Monolayers exposed to 10 nM prolactin for 24 hr revealed an inhibition of 40% in ouabain-sensitive 86Rb+ uptake, a sensitive measure of pump-mediated transport. These experiments suggest that the unique transport properties of prostate may depend, at least in part, on a complicated pattern of Na,K-pump expression and regulation. 相似文献
86.
87.
Multiple activities contribute to Pc2 E3 function 总被引:1,自引:0,他引:1
Pc2 is a polycomb protein, which has SUMO E3 activity for the corepressors CtBP and CtBP2. Here we demonstrate that, in vivo, Pc2 adapter function contributes to enhancement of CtBP sumoylation. Mutation of the CtBP binding site on Pc2 abolishes E3 activity toward CtBP. However, a carboxyl-terminal fragment of Pc2 that recruits both Ubc9 and CtBP lacks E3 activity. We identify a second domain, which, when coexpressed with the carboxyl-terminal adapter region, restores E3 function. In vitro, this domain has E3 activity in isolation, suggesting that it is a functional domain, and that adapter function is required to selectively corecruit E2 and substrate in vivo. These results demonstrate the presence of two domains in Pc2 that contribute to full in vivo E3 activity, and suggest that SUMO E3s are more than simple platforms to which E2 and substrate bind. 相似文献
88.
Nicolae Solcan Alette Brinth Dianfan Li Syed TA Shah Martin Caffrey Simon Newstead 《EMBO reports》2014,15(8):886-893
An enigma in the field of peptide transport is the structural basis for ligand promiscuity, as exemplified by PepT1, the mammalian plasma membrane peptide transporter. Here, we present crystal structures of di‐ and tripeptide‐bound complexes of a bacterial homologue of PepT1, which reveal at least two mechanisms for peptide recognition that operate within a single, centrally located binding site. The dipeptide was orientated laterally in the binding site, whereas the tripeptide revealed an alternative vertical binding mode. The co‐crystal structures combined with functional studies reveal that biochemically distinct peptide‐binding sites likely operate within the POT/PTR family of proton‐coupled symporters and suggest that transport promiscuity has arisen in part through the ability of the binding site to accommodate peptides in multiple orientations for transport. 相似文献
89.
近年来胃癌的发病率有所下降,相比之下胃食管结合部腺癌的发病率却快速增长。手术治疗仍然是早期食管胃结合部腺癌的标准治疗方法,同时手术联合化疗、放化疗治疗食管胃结合部腺癌也逐渐得到国际认可。尽管在手术治疗、放疗和化疗治疗技术得到完善和改进,但食管癌和食管胃结合部腺癌的预后仍然较差。目前有数个大型临床随机对照试验数据支持对食管下端和食管胃交界部腺癌使用术前联合化疗,但辅助治疗的贡献仍不能确定。最近有meta分析表明手术联合化疗、放化疗可以提高胃食管结合部腺癌患者术后存活率,但也有一些临床随机试验的数据表明手术联合化疗、放化疗并无明显好处。本文通过总结最新的临床试验及meta分析结果,阐述不同的可切除的胃食管结合部腺癌的联合治疗方法。 相似文献
90.
Slawson EE Shaffer CD Malone CD Leung W Kellmann E Shevchek RB Craig CA Bloom SM Bogenpohl J Dee J Morimoto ET Myoung J Nett AS Ozsolak F Tittiger ME Zeug A Pardue ML Buhler J Mardis ER Elgin SC 《Genome biology》2006,7(2):R15-18