Rapid isolation and characterization of polymorphic microsatellite loci in the mud crab, Scylla paramamosain (Portunidae)

Scylla paramamosain is a widespread and commercially important species of coastal marine crab. We identified 13 polymorphic microsatellite loci from a genome library constructed with 5'-anchored PCR method. Thirty-two S. paramamosain from the East China Sea were used to analyze the characteristics of these loci. The number of alleles per locus ranged from 3 to 8, with a mean of 5.923. Observed and expected heterozygosities ranged from 0.500 to 0.875 and from 0.500 to 0.859, respectively. Eleven of the 13 loci were highly polymorphic (polymorphic information content >0.5). All of the 13 novel loci were in Hardy-Weinberg equilibrium after Bonferroni's correction (P < 0.0038). There was no null allele, stuttering errors or evidence of allelic dropout in any of the loci analyzed by MICRO-CHECKER. According to pairwise tests, no significant linkage disequilibrium was found among the 13 loci (P < 0.0038, adjusted value). These novel developed microsatellites will be useful for studies of genetic variation, population structure, conservation genetics, and molecular-assisted selective breeding of S. paramamosain.     

泛素样蛋白ISG15抗病毒机制研究进展

ISG15(Interferon stimulated gene 15,ISG15)蛋白是由干扰素诱导产生的一种泛素样蛋白分子,分子量大小约为15kD。ISG15同泛素分子相类似可以被共价结合于其他蛋白分子上,这种现象称为ISG化(ISGylation)现象。ISG化系统包括ISG15、UBE1L、UBCH8和HERC5四类蛋白分子,协同完成ISG化过程。ISG15及ISG化系统在抗病毒反应中具有重要作用。近几年对于ISG15的抗病毒作用和机制的研究已经有了很大的突破,ISG15的抗病毒作用也越来越受到人们重视,了解清楚ISG15抗病毒机制对于研制新的抗病毒药物及提出新的抗病毒策略具有重要意义。本文对ISG15在不同种病毒中的抗病毒机制研究进展进行了简要综述。     

Targeting A20 Decreases Glioma Stem Cell Survival and Tumor Growth

Glioblastomas are deadly cancers that display a functional cellular hierarchy maintained by self-renewing glioblastoma stem cells (GSCs). GSCs are regulated by molecular pathways distinct from the bulk tumor that may be useful therapeutic targets. We determined that A20 (TNFAIP3), a regulator of cell survival and the NF-κB pathway, is overexpressed in GSCs relative to non-stem glioblastoma cells at both the mRNA and protein levels. To determine the functional significance of A20 in GSCs, we targeted A20 expression with lentiviral-mediated delivery of short hairpin RNA (shRNA). Inhibiting A20 expression decreased GSC growth and survival through mechanisms associated with decreased cell-cycle progression and decreased phosphorylation of p65/RelA. Elevated levels of A20 in GSCs contributed to apoptotic resistance: GSCs were less susceptible to TNFα-induced cell death than matched non-stem glioma cells, but A20 knockdown sensitized GSCs to TNFα-mediated apoptosis. The decreased survival of GSCs upon A20 knockdown contributed to the reduced ability of these cells to self-renew in primary and secondary neurosphere formation assays. The tumorigenic potential of GSCs was decreased with A20 targeting, resulting in increased survival of mice bearing human glioma xenografts. In silico analysis of a glioma patient genomic database indicates that A20 overexpression and amplification is inversely correlated with survival. Together these data indicate that A20 contributes to glioma maintenance through effects on the glioma stem cell subpopulation. Although inactivating mutations in A20 in lymphoma suggest A20 can act as a tumor suppressor, similar point mutations have not been identified through glioma genomic sequencing: in fact, our data suggest A20 may function as a tumor enhancer in glioma through promotion of GSC survival. A20 anticancer therapies should therefore be viewed with caution as effects will likely differ depending on the tumor type.     

Protein interactors of acyl-CoA-binding protein ACBP2 mediate cadmium tolerance in Arabidopsis

In our recent paper in the Plant Journal, we reported that Arabidopsis thaliana lysophospholipase 2 (lysoPL2) binds acyl-CoA-binding protein 2 (ACBP2) to mediate cadmium [Cd(II)] tolerance in transgenic Arabidopsis. ACBP2 contains ankyrin repeats that have been previously shown to mediate protein-protein interactions with an ethylene-responsive element binding protein (AtEBP) and a farnesylated protein 6 (AtFP6). Transgenic Arabidopsis ACBP2-overexpressors, lysoPL2-overexpressors and AtFP6-overexpressors all display enhanced Cd(II) tolerance, in comparison to wild type, suggesting that ACBP2 and its protein partners work together to mediate Cd(II) tolerance. Given that recombinant ACBP2 and AtFP6 can independently bind Cd(II) in vitro, they may be able to participate in Cd(II) translocation. The binding of recombinant ACBP2 to [¹⁴C]linoleoyl-CoA and [¹⁴C]linolenoyl-CoA implies its role in phospholipid repair. In conclusion, ACBP2 can mediate tolerance to Cd(II)-induced oxidative stress by interacting with two protein partners, AtFP6 and lysoPL2. Observations that ACBP2 also binds lysophosphatidylcholine (lysoPC) in vitro and that recombinant lysoPL2 degrades lysoPC, further confirm an interactive role for ACBP2 and lysoPL2 in overcoming Cd(II)-induced stress.Key words: acyl-CoA-binding protein, cadmium, hydrogen peroxide, lysophospholipase, oxidative stressAcyl-CoA-binding proteins (ACBP1 to ACBP6) are encoded by a multigene family in Arabidopsis thaliana.¹ These ACBP proteins are well studied in Arabidopsis in comparison to other organisms,^1–4 and are located in various subcellular compartments.¹ Plasma membranelocalized ACBP1 and ACBP2 contain ankyrin repeats that have been shown to function in protein-protein interactions.^5,6 ACBP1 and ACBP2 which share 76.9% amino acid identity also confer tolerance in transgenic Arabidopsis to lead [Pb(II)] and Cd(II), respectively.^1,5,7 Since recombinant ACBP1 and ACBP2 bind linolenoyl-CoA and linoleoyl-CoA in vitro, they may possibly be involved in phospholipid repair in response to heavy metal stress at the plasma membrane.^5,7 In contrast, ACBP3 is an extracellularly-localized protein⁸ while ACBP4, ACBP5 and ACBP6 are localized to cytosol.^9,10 ACBP1 and ACBP6 have recently been shown to be involved in freezing stress.^9,11 ACBP4 and ACBP5 bind oleoyl-CoA ester and their mRNA expressions are lightregulated.^12,13 Besides acyl-CoA esters, some ACBPs also bind phospholipids.^9,11,13 To investigate the biological function of ACBP2, we have proceeded to establish its interactors at the ankyrin repeats, including AtFP6,⁵ AtEBP⁶ and now lysoPL2 in the Plant Journal paper. While the significance in the interaction of ACBP2 with AtEBP awaits further investigations, some parallels can be drawn between those of ACBP2 with AtFP6 and with lysoPL2.     

X-ray crystal structure of Desulfovibrio vulgaris rubrerythrin with zinc substituted into the [Fe(SCys)4] site and alternative diiron site structures

The X-ray crystal structure of recombinant Desulfovibrio vulgaris rubrerythrin (Rbr) that was subjected to metal constitution first with zinc and then iron, yielding ZnS(4)Rbr, is reported. A [Zn(SCys)(4)] site with no iron and a diiron site with no appreciable zinc in ZnS(4)Rbr were confirmed by analysis of the anomalous scattering data. Partial reduction of the diiron site occurred during the synchrotron X-ray irradiation at 95 K, resulting in two different diiron site structures in the ZnS(4)Rbr crystal. These two structures can be classified as containing mixed-valent Fe1(III)(mu-OH(-))(mu-GluCO(2)(-))(2)Fe2(II) and Fe1(II)(mu-GluCO(2)(-))(2)Fe2(III)-OH(-) cores. The data do not show any evidence for alternative positions of the protein or solvent ligands. The iron and ligand positions of the solvent-bridged site are close to those of the diferric site in all-iron Rbr. The diiron site with only the two carboxylato bridges differs by an approximately 2 A shift in the position of Fe1, which changes from six- to four-coordination. The Fe1- - -Fe2 distance (3.6 A) in this latter site is significantly longer than that of the site with the additional solvent bridge (3.4 A) but significantly shorter than that previously reported for the diferrous site (4.0 A) in all-iron Rbr. The apparent redox-induced movement of Fe1 at 95 K in the ZnS(4)Rbr crystal implies an extremely low activation barrier, which is consistent with the rapid (approximately 30 s(-1)) room temperature turnover of the all-iron Rbr during its catalysis of two-electron reduction of hydrogen peroxide. ZnS(4)Rbr does not show peroxidase activity, presumably because the [Zn(SCys)(4)] site, unlike the [Fe(SCys)(4)] site, cannot mediate electron transfer to the diiron site. One or both of the diiron site structures in the cryoreduced ZnS(4)Rbr crystal are likely to represent that (those) of transient mixed-valent diiron site(s) that must occur upon return of the diferric to the diferrous oxidation level during peroxidase turnover.     

Analyses of genetic structure of Tibeto-Burman populations reveals sex-biased admixture in southern Tibeto-Burmans

An unequal contribution of male and female lineages from parental populations to admixed ones is not uncommon in the American continents, as a consequence of directional gene flow from European men into African and Hispanic Americans in the past several centuries. However, little is known about sex-biased admixture in East Asia, where substantial migrations are recorded. Tibeto-Burman (TB) populations were historically derived from ancient tribes of northwestern China and subsequently moved to the south, where they admixed with the southern natives during the past 2600 years. They are currently extensively distributed in China and Southeast Asia. In this study, we analyze the variations of 965 Y chromosomes and 754 mtDNAs in >20 TB populations from China. By examining the haplotype group distributions of Y-chromosome and mtDNA markers and their principal components, we show that the genetic structure of the extant southern Tibeto-Burman (STB) populations were primarily formed by two parental groups: northern immigrants and native southerners. Furthermore, the admixture has a bias between male and female lineages, with a stronger influence of northern immigrants on the male lineages (approximately 62%) and with the southern natives contributing more extensively to the female lineages (approximately 56%) in the extant STBs. This is the first genetic evidence revealing sex-biased admixture in STB populations, which has genetic, historical, and anthropological implications.     

Solution structure of 2',5' d(G4C4). Relevance to topological restrictions and nature's choice of phosphodiester links.

The NMR structure of 2',5' d(GGGGCCCC) was determined to gain insights into the structural differences between 2',5'- and 3',5'-linked DNA duplexes that may be relevant in elucidating nature's choice of sugar-phosphate links to encode genetic information. The oligomer assumes a duplex with extended nucleotide repeats formed out of mostly N-type sugar puckers. With the exception of the 5'-terminal guanine that assumes the syn glycosyl conformation, all other bases prefer the anti glycosyl conformation. Base pairs in the duplex exhibit slide (-1.96 A) and intermediate values for X-displacement (-3.23 A), as in ADNA, while their inclination to the helical axis is not prominent. Major and minor grooves display features intermediate to A and BDNA. The duplex structure of iso d(GGGGCCCC) may therefore be best characterized as a hybrid of A and BDNA. Importantly, the results confirm that even 3' deoxy 2',5' DNA supports duplex formation only in the presence of distinct slide (>or=-1.6 A) and X-displacement (>or=-2.5 A) for base pairs, and hence does not favor an ideal BDNA topology characterized by their near-zero values. Such restrictions on base pair movements in 2',5' DNA, which are clearly absent in 3',5' DNA, are expected to impose constraints on its ability for deformability of the kind observed in DNA during its compaction and interaction with proteins. It is therefore conceivable that selection pressure relating to the optimization of topological features might have been a factor in the rejection of 2',5' links in preference to 3',5' links.