Gibberellin: inhibitor of an inhibitor of...?

Gibberellin is an endogenous plant growth regulator. Here, we describe our present understanding of how gibberellin regulates plant growth, using recent results gained from studies of gibberellin-signalling mutants of Arabidopsis. These results show that a signalling pathway represses plant growth and that gibberellin releases this repression. In consequence, the well-known growth-promoting properties of gibberellin are due to its activity as an "inhibitor of an inhibitor" [Brian Pw. Sym Soc. Exp Bio 1957; 11:166-182 (Ref. 1)] of plant growth.     

The Evolutionarily Conserved Eukaryotic Arginine Attenuator Peptide Regulates the Movement of Ribosomes That Have Translated It

Translation of the upstream open reading frame (uORF) in the 5′ leader segment of the Neurospora crassa arg-2 mRNA causes reduced initiation at a downstream start codon when arginine is plentiful. Previous examination of this translational attenuation mechanism using a primer-extension inhibition (toeprint) assay in a homologous N. crassa cell-free translation system showed that arginine causes ribosomes to stall at the uORF termination codon. This stalling apparently regulates translation by preventing trailing scanning ribosomes from reaching the downstream start codon. Here we provide evidence that neither the distance between the uORF stop codon and the downstream initiation codon nor the nature of the stop codon used to terminate translation of the uORF-encoded arginine attenuator peptide (AAP) is important for regulation. Furthermore, translation of the AAP coding region regulates synthesis of the firefly luciferase polypeptide when it is fused directly at the N terminus of that polypeptide. In this case, the elongating ribosome stalls in response to Arg soon after it translates the AAP coding region. Regulation by this eukaryotic leader peptide thus appears to be exerted through a novel mechanism of cis-acting translational control.     

Identification of rCop-1, a New Member of the CCN Protein Family,as a Negative Regulator for Cell Transformation

By using a model system for cell transformation mediated by the cooperation of the activated H-ras oncogene and the inactivated p53 tumor suppressor gene, rCop-1 was identified by mRNA differential display as a gene whose expression became lost after cell transformation. Homology analysis indicates that rCop-1 belongs to an emerging cysteine-rich growth regulator family called CCN, which includes connective-tissue growth factor, CYR61, CEF10 (v-src inducible), and the product of the nov proto-oncogene. Unlike the other members of the CCN gene family, rCop-1 is not an immediate-early gene, it lacks the conserved C-terminal domain which was shown to confer both growth-stimulating and heparin-binding activities, and its expression is lost in cells transformed by a variety of mechanisms. Ectopic expression of rCop-1 by retroviral gene transfers led to cell death in a transformation-specific manner. These results suggest that rCop-1 represents a new class of CCN family proteins that have functions opposing those of the previously identified members.Oncogenic conversion of a normal cell into a tumor cell requires multiple genetic alterations (12). Of particular interest is the fact that mutations in both ras oncogenes (3) and the p53 tumor suppressor gene cooperate in transformation of mammalian cells (11). Mutations in both ras and the p53 gene were also found at high frequencies in a variety of human cancers, including those of the colon, lung, and pancreas (2, 18). It has been proposed that both p53 and Ras function, whether directly or through other signaling molecules, to control expression of genes that are important for cell growth and differentiation (13, 17, 37). To this end, several ras target genes (10) and p53 target genes, including those encoding p21/CIP1/WAF1, an inhibitor of G₁ cyclin-dependent kinase (9); Mdm-2, a negative regulator of p53 (1); GADD45, a protein involved in DNA repair (36); and Bax, which promotes apoptosis (28), have been identified. Most of these genes, except p21/CIP1/WAF1, which was cloned by subtractive hybridization, were identified by the candidate gene hypothesis. Recently, more p53 target genes have been isolated by the differential display technique, including those coding for cyclin G (31); MAP4, a microtubule-associated protein negatively regulated by p53 (29); and PAG608, a novel nuclear zinc finger protein whose overexpression promotes apoptosis (14). Functional characterizations of these genes have shed light on the role of p53 in cell cycle control and apoptosis. However, genes that mediate tumor suppression activity by p53 remain elusive.The fact that neither the inactivation of p53 nor the activation of Ras alone is able to transform primary mammalian cells (34), whereas both mutations together can do so, suggests that genes regulated by p53 and Ras cooperate in upsetting normal cell growth control cells (11). Using differential display (22), we set out to identify genes whose expression is altered by both mutant ras and p53 by comparing the mRNA expression profiles of normal rat embryo fibroblasts (REFs) and their derivatives transformed by either a constitutively inactivated or a temperature-sensitive mutant p53 in cooperation with the activated H-ras oncogene (11, 27). In this report we describe the identification and give a functional characterization of rCop-1, a gene whose expression is abolished by cell transformation. By sequence homology, rCop-1 was found to belong to an emerging cysteine-rich growth regulator family called CCN (which stands for connective-tissue growth factor [CTGF], CEF10/Cyr61, and Nov) (4). Here we show that rCop-1 may represent a novel class of CCN family proteins based on its unique cell cycle expression pattern, its lack of the C-terminal (CT) domain conserved in all CCN proteins, its loss of expression in all transformed cells analyzed, and its ability to confer cytotoxicity to the transformed cells.     

Anti-AIDS agents 82: Synthesis of seco-(3′R,4′R)-3′,4′-di-O-(S)-camphanoyl-(+)-cis-khellactone (DCK) derivatives as novel anti-HIV agents

Thirteen novel seco-DCK analogs (4–16) with several new skeletons were designed, synthesized and screened for in vitro anti-HIV-1 activity. Among them, three compounds (5, 13, and 16) showed moderate activity, and compound 9 exhibited the best activity with an EC₅₀ value of 0.058 μM and a therapeutic index (TI) of 1000. The activity of 9 was better than that of 4-methyl DCK (2, EC₅₀: 0.126 μM, TI: 301.2) in the same assay. Additionally, 9 also showed antiviral activity against a multi-RT inhibitor-resistant strain (RTMDR), which is insensitive to most DCK analogs. Compared with 2, compound 9 has a less complex structure, fewer hydrogen-bond acceptors, and a reduced log P value. Therefore, it is likely to exhibit better ADME, and appears to be a promising new lead for further development as an anti-HIV candidate.     

Singing behavior and singing functions of black‐crested gibbons (Nomascus concolor jingdongensis) at Mt. Wuliang,central Yunnan,China

We used data on loud duetted and solo songs collected from one habituated polygynous group of black‐crested gibbons (Nomascus concolor jingdongensis) on Mt. Wuliang, Yunnan, to test several hypotheses about the functions of these songs. The major functions proposed for loud gibbon songs include resource defense, mate defense, pairbonding, group cohesion and mate attraction. Duet bouts are generally initiated by adult males, who select the highest trees near to ridges or on steep slopes as singing trees. Such trees facilitate voice transmission and inter‐group communication. Singing trees tended to be located near important food patches and sleeping sites, which supports the resource defense hypothesis. The adult male and two adult females always sang interactively, alternating male phrases with the females' stereotyped great calls, to produce the duets, and females rarely produced great calls if they were more than 30 m from the male. The two females usually produced great calls synchronously during the duet, especially when they were close together. These features support both the mate defense and pairbonding hypotheses. The number of great calls and their degree of synchrony transmit information about spatial relationships and possibly pairbond strength to members to neighboring groups and floating animals. During or after the duet bouts, the adult females and juvenile moved toward to the adult male; and group members maintained a close spatial relationship, which supports the group cohesion hypothesis. Other incidents observed suggest a mate competition role for duets. The adult male always sang when the females started duetting with the subadult male. The subadult male sang solo bouts, but they were not more frequent or longer than bouts initiated by the adult male. Although mate attraction is the likely function of subadult solos, it was not convincingly demonstrated. In conclusion, all hypotheses concerning the function of singing are supported by at least some of the data, and none can be excluded. Am. J. Primatol. 71:539–547, 2009. © 2009 Wiley‐Liss, Inc.     

A genome map of Salmonella enterica serovar Agona: numerous insertions and deletions reflecting the evolutionary history of a human pathogen

Salmonella enterica serovar Agona is an important zoonotic pathogen, causing serious human illness worldwide, but knowledge about its genetics and evolution, especially regarding the genomic events that might have contributed to the formation of S . Agona as an important pathogen, is lacking. As a first step toward understanding this pathogen and characterizing its genomic differences with other salmonellae, we constructed a physical map of S . Agona in strain SARB1 using I-CeuI, XbaI, AvrII and Tn 10 insertions with pulsed-field gel electrophoresis techniques. On the 4815-kb genomic map, we located 82 genes, revealed one inversion of about 1000 kb and resolved seven deletions and seven insertions ranging from 10 to 67 kb relative to the genome of Salmonella typhimurium LT2. These genomic features clearly distinguish S . Agona from other previously analyzed salmonellae and provide clues to the molecular basis for its genomic divergence. Additionally, these kinds of physical maps, combined with emerging high-speed sequencing technologies, such as the Solexa or SOLiD techniques, which require a pre-existing high-resolution physical map such as the S . Agona map reported here, will play important roles in genomic comparative studies of bacteria involving large numbers of strains.     

Improving the accuracy of depth of anaesthesia using modified detrended fluctuation analysis method

This paper presents a modified detrended fluctuation analysis (MDFA) to improve the monitoring accuracy of the depth of anaesthesia (DoA). We first use MDFA to classify anaesthesia state levels into awake, light, moderate, deep and very deep states. Then we build up five zones using linear regression method from very deep anaesthesia state to awake state, corresponding with different box sizes. Finally, the Lagrange method is applied to compute the DoA. Comparing with the most popular Bispectral Index (BIS) method, our modified DFA method extends the ranges of the moderate anaesthesia, deep anaesthesia and very deep anaesthesia to provide more information about the DoA. This extension is very significant in the clinical perspective as these states are within the ranges for operations and need more attention. Simulation results demonstrate that the new technique monitors the DoA in all anaesthesia states accurately.     

Structural analysis and antitussive evaluation of five novel esters of verticinone and bile acids

Shedan-Chuanbei powder, a complex of traditional Chinese medicine preparation, which consists of Snake Bile (Chinese name “Shedan”) and Fritillariae Cirrhosae (Chinese name “Chuanbei”), is the most popular antitussive and expectorant formulation in Chinese communities. However, the clinical application of Shedan-Chuanbei powder is now stringently limited because of the shortage of the two crude medicinal materials, especially for the sake of animal protection. In addition, the inherent defects of the most of the complex of traditional Chinese medicine such as the indistinct basal pharmacodynamic materials and the difficulties in quality control had blocked them heading into the international medicinal market. So we attempted to seek new substitute for Shedan-Chuanbei powder for antitussive drugs. In order to gain some new compounds with better bioactivity and attenuated toxicity, we tried to combine two kinds of drugs through ester bond. Enlightened with “combination principle” in drug discovery, we synthesized five novel esters of verticinone and bile acids, both of which are the major bioactive components in Shedan-Chuanbei powder. We then evaluated the antitussive activity and the acute toxicity of the five ester-linked compounds. The five ester-linked compounds had much more potent antitussive activity and expectorant activity than single bile acids at the same doses, and had equivalent antitussive activity and expectorant activity in comparison with about double moles dose of the monomer verticinone. Especially, cholic acid–verticinone ester had much more potent antitussive effects than the monomer verticinone or cholic acid at the same dose. A further acute toxicity study showed that the LD₅₀ values of the five ester-linked compounds exceeded 3.5 g/kg by intraperitoneal injection in mice. Based on the studies of pharmacology and acute toxicity, the five ester-linked compounds have synergic pharmacodynamic action and attenuated toxicity compared with single verticinone and single bile acids.     

Tissue distribution of puerarin and its conjugated metabolites in rats assessed by liquid chromatography–tandem mass spectrometry

Puerarin (an isoflavone C-glucoside from kudzu root) has been the focus of several studies investigating its potential effects on health benefits. In this study, we determined single dose tissue distribution of puerarin and its metabolites in order to examine whether they undergo selective uptake by specific organs. Puerarin was administered orally (50 mg/kg) to rats and the concentration of puerarin in tissue compartments was determined using liquid chromatography–tandem mass spectrometry (LC–MS/MS). Puerarin was widely distributed in rat tissues with highest concentrations in lungs (799±411.6 ng/g wet tissues). In addition, we examined the excretion of puerarin into the bile. LC–MS/MS analysis of bile samples collected after infusing puerarin directly into the portal vein indicated that puerarin was excreted into the bile predominantly in the form of unconjugated puerarin. This report identifying puerarin in several organs including kidney and pancreas may explain its beneficial effects in diabetes.