Skp2 regulates G2/M progression in a p53-dependent manner

Targeted proteasomal degradation mediated by E3 ubiquitin ligases controls cell cycle progression, and alterations in their activities likely contribute to malignant cell proliferation. S phase kinase-associated protein 2 (Skp2) is the F-box component of an E3 ubiquitin ligase complex that targets p27^Kip1 and cyclin E1 to the proteasome. In human melanoma, Skp2 is highly expressed, regulated by mutant B-RAF, and required for cell growth. We show that Skp2 depletion in melanoma cells resulted in a tetraploid cell cycle arrest. Surprisingly, co-knockdown of p27^Kip1 or cyclin E1 failed to prevent the tetraploid arrest induced by Skp2 knockdown. Enhanced Aurora A phosphorylation and repression of G2/M regulators cyclin B1, cyclin-dependent kinase 1, and cyclin A indicated a G2/early M phase arrest in Skp2-depleted cells. Furthermore, expression of nuclear localized cyclin B1 prevented tetraploid accumulation after Skp2 knockdown. The p53 status is most frequently wild type in melanoma, and the tetraploid arrest and down-regulation of G2/M regulatory genes were strongly dependent on wild-type p53 expression. In mutant p53 melanoma lines, Skp2 depletion did not induce cell cycle arrest despite up-regulation of p27^Kip1. These data indicate that elevated Skp2 expression may overcome p53-dependent cell cycle checkpoints in melanoma cells and highlight Skp2 actions that are independent of p27^Kip1 degradation.     

Asymmetric reduction of prochiral ketones to chiral alcohols catalyzed by plants tissue

As an important organic compound, chiral alcohols are the key chiral building blocks to many single enantiomer pharmaceuticals. Asymmetric reduction of the corresponding prochiral ketones to produce the chiral alcohols by biocatalysis is one of the most promising routes. Asymmetric reduction of different kinds of non-natural prochiral ketones catalyzed by various plants tissue was studied in this work. Acetophenone, 4'-chloroacetophenone and ethyl 4-chloroacetoacetate were chosen as the model substrates for simple ketone, halogen-containing aromatic ketone and beta-ketoesters, respectively. Apple (Malus pumila), carrot (Daucus carota), cucumber (Cucumis sativus), onion (Allium cepa), potato (Soanum tuberosum), radish (Raphanus sativus) and sweet potato (Ipomoea batatas) were chosen as the biocatalysts. It was found that these kinds of prochiral ketoness could be reduced by these plants tissue with high enantioselectivity. Both R- and S-form configuration chiral alcohols could be obtained. The e.e. and chemical yield could reach about 98 and 80% respectively for acetophenone and 4'-chloroacetophenone reduction reaction with favorable plant tissue. And the e.e. and yield for ethyl 4-chloroacetoacetate reduction reaction was about 91 and 45% respectively.     

Prediction of hybrid grain yield performances in Indica Rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) with effect-increasing loci

One hundred and fifty-one rice hybrids produced in two sets of half-dialell crosses and their parents (13 cytoplasmic male sterile lines and 19 restorers) were used to predict the F₁ performances of seven yield traits through the parental genetic distances (GD) based on SSR markers. The positive loci (PL) and effect-increasing loci (IL), which were screened from SSR polymorphic loci by the F₁ traits of 32 parents, together with total loci (TL), were utilized to estimate parental GD and the models were found to predict the traits of hybrids derived from different parents, fixed parents, and different environments, respectively. The results were as follows: (1) 550 polymorphic loci were detected from 174 SSR markers: a dendrogram based on these loci could separate all the sterile and restorer lines used in the present study, which indicated that parental genetic diversity of F₁ was large; (2) the correlations between F₁ traits and parental GDs based on IL ranged from 0.61 to 0.87 with a mean of 0.76, and they were higher than those on TL or on PL; (3) predictions based on IL for F₁ traits (except grain weight per plant) derived from different environments were ideal, but worse for F₁ traits derived from different parents; and (4) IL was more effective than TL and PL in predicting traits of F₁ with fixed parents, and predictions for fixed restorer combinations were more effective than those for fixed sterile line combinations. These results should facilitate molecular prediction for hybrid yield and other traits by means of both elite sterile and restorer lines.     

Nitro as a novel zinc-binding group in the inhibition of carboxypeptidase A

2-Substituted 3-nitropropanoic acids were designed and synthesized as inhibitors against carboxypeptidase A (CPA). (R)-2-Benzyl- 3-nitropropanoic acid showed a potent inhibition against CPA (K(i)=0.15 microM). X-ray crystallography discloses that the nitro group well mimics the transition state occurred in the hydrolysis catalyzed by CPA, that is, an O,O'-bidentate coordination to the zinc ion and the two respective hydrogen bonds with Glu-270 and Arg-127. Because the nitro group is a planar species, we proposed (R)-2-benzyl-3-nitropropanoic acid as a pseudo-transition-state analog inhibitor against CPA.     

Cell-cycle synchronization of fibroblasts derived from transgenic cloned cattle ear skin: effects of serum starvation, roscovitine and contact inhibition

The purpose of the present study was to evaluate the effects of serum-starvation, contact-inhibition and roscovitine treatments on cell-cycle synchronization at the G0/G1 stage of ear skin fibroblasts isolated from transgenic cloned cattle. The developmental competence of re-cloned embryos was also examined. Our results showed that the proportion of G0/G1 cells from the serum-starved group at 3, 4 or 5 days was significantly higher compared with 1 or 2 days only (91.5, 91.7 and 93.5% versus 90.1 and 88.8%, respectively, p < 0.05); whilst there was no statistical difference among cells at 3, 4 or 5 days. For roscovitine-treated cells, the proportion of G0/G1 cells at 2, 3, 4 or 5 days was significantly higher than those treated for 1 day only (91.1, 90.1, 89.4 and 91.3% versus 86.51%, respectively, p < 0.05). The proportion of contact-inhibited G0/G1 cells rose significantly with treatment time, but was similar at 3, 4 and 5 days (89.4, 90.4, 91.4, 91.6 and 92.1%, respectively, p < 0.05). The efficiency of obtaining G0/G1 phase cells was lower when roscovitine treatment was employed to synchronize the cell cycle compared with the serum-starvation and contact-inhibition methods (89.7 versus 91.1% and 91.0%, p < 0.05). Moreover, obvious differences were observed in the rate of fused couplets and blastocysts (89.88 +/- 2.70 versus 87.40 +/- 5.13; 44.10 +/- 8.62 versus 58.38 +/- 13.28, respectively, p < 0.05), when nuclear transfer embryos were reconstructed using donors cells that had been serum starved or contact inhibited for 3 days. Our data indicate that 3 day treatment is feasible for harvesting sufficient G0/G1 cells to produce re-cloned transgenic bovine embryos, regardless of whether serum-starvation, contact-inhibition or roscovitine treatments are used as the synchronization methods.     

2-Phenoxy-indan-1-one derivatives as acetylcholinesterase inhibitors: a study on the importance of modifications at the side chain on the activity

As a part of our project aimed at developing new agents of potential application in AD, a new series of 2-phenoxy-indan-1-one derivatives which possess alkylamine side chain were designed, synthesized, and evaluated for their inhibitory activity against AChE and BuChE. Most of the compounds were found to inhibit AChE in the nanomolar range. The optimum inhibitor 3g exhibited 34-fold increase in AChE inhibition than donepezil and displayed neuroprotective effect against H(2)O(2)-induced cell death.     

Potent and selective small molecule NS3 serine protease inhibitors of Hepatitis C virus with dichlorocyclopropylproline as P2 residue

Starting from a pentapeptide Hepatitis C virus NS3 protease inhibitor, a number of alpha-ketoamide inhibitors based on novel dichlorocyclopropylproline P2 core were synthesized and investigated for their HCV NS3 serine protease activity. The key intermediate 3,4-dichlorocyclopropylproline was obtained through a dichloro carbene insertion to 3,4-dehydroproline. The size of the molecules was reduced significantly through a series of truncations of the initial pentapeptide. By varying P1 side chain in length and size, potency and selectivity were improved. A variety of aliphatic carbamate and urea capping groups were examined. In general, compounds with urea cappings were more potent and selective than their carbamate counterparts. The most potent compound was a tert-butyl urea analog. Variations at P3 position were also investigated. Among the three residues incorporated, tert-leucine was clearly superior, leading to compounds that had excellent enzyme potency and selectivity. The most potent compound achieved cell-based replicon assay EC50 of 40 nM. The most promising compound of all had excellent potency in both enzyme (Ki* = 9 nM) and replicon assays (EC50 = 100 nM). Its bioavailabilities were above 10% in all three animal species (rats, monkeys, and dogs). It has provided a lead for future investigations.     

Expression pattern and polymorphism of three microsatellite markers in the porcine CA3 gene

Carbonic anhydrase III (CA3) is an abundant muscle protein characteristic of adult type-1, slow-twitch, muscle fibres. In order to further understand the functions of the porcine CA3 protein in muscle, the temporal and spatial distributions of its gene product were analysed and the association between the presence of specific polymorphisms and carcass traits in the pig was also examined. Real-time PCR revealed that the CA3 mRNA expression showed no differences with age in skeletal muscles from Yorkshire pigs at postnatal day-1, month-2, and month-4. We provide the first evidence that CA3 is differentially expressed in the skeletal muscle of Yorkshire and Meishan pig breeds. In addition, the whole pig genomic DNA sequence of CA3 was investigated and shown to contain seven exons and six introns. Comparative sequencing of the gene from three pig breeds revealed the existence of microsatellite SJ160 in intron 5 and microsatellite SJ158 and a novel microsatellite marker that includes a tandem repeat of (TC)_n in intron 4. We also determined the allele number and frequencies of the three loci in seven pig breeds and found that they are low polymorphic microsatellite markers. Statistical analysis showed that the CA3 microsatellite polymorphism was associated with dressing percentage, internal fat rate, carcass length, rib number and backfat thickness in the pig.