Histone deacetylase 1: a target of 9-hydroxystearic acid in the inhibition of cell growth in human colon cancer

Recent studies have shown that an endogenous lipoperoxidation product, 9-hydroxystearic acid (9-HSA), acts in colon carcinoma cells (HT29) as a growth inhibitor by inducing p21(WAF1) in an immediate-early, p53-independent manner and that p21(WAF1) is required for 9-HSA-mediated growth arrest in HT29 cells. It is conceivable, therefore, to hypothesize that the cytostatic effect induced by this agent is at least partially associated with a molecular mechanism that involves histone deacetylase 1 (HDAC1) inhibition, as demonstrated for sodium butyrate and other specific inhibitors, such as trichostatin A and hydroxamic acids. Here, we show that, after administration, 9-HSA causes an accumulation of hyperacetylated histones and strongly inhibits the activity of HDAC1. The interaction of 9-HSA with the catalytic site of the enzyme has been highlighted by computational modeling of the human HDAC1, using its homolog from the hyperthermophilic Aquifex aeolicus as a template. Consistent with the experimental data, we find that 9-HSA can bind to the active site of the protein, showing that the inhibition of the enzyme can be explained at the molecular level by the ligand-protein interaction.     

Acyl-coenzyme A binding protein expression alters liver fatty acyl-coenzyme A metabolism

Although studies in vitro and in yeast suggest that acyl-CoA binding protein ACBP may modulate long-chain fatty acyl-CoA (LCFA-CoA) distribution, its physiological function in mammals is unresolved. To address this issue, the effect of ACBP on liver LCFA-CoA pool size, acyl chain composition, distribution, and transacylation into more complex lipids was examined in transgenic mice expressing a higher level of ACBP. While ACBP transgenic mice did not exhibit altered body or liver weight, liver LCFA-CoA pool size increased by 69%, preferentially in saturated and polyunsaturated, but not monounsaturated, LCFA-CoAs. Intracellular LCFA-CoA distribution was also altered such that the ratio of LCFA-CoA content in (membranes, organelles)/cytosol increased 2.7-fold, especially in microsomes but not mitochondria. The increased distribution of specific LCFA-CoAs to the membrane/organelle and microsomal fractions followed the same order as the relative LCFA-CoA binding affinity exhibited by murine recombinant ACBP: saturated > monounsaturated > polyunsaturated C14-C22 LCFA-CoAs. Consistent with the altered microsomal LCFA-CoA level and distribution, enzymatic activity of liver microsomal glycerol-3-phosphate acyltransferase (GPAT) increased 4-fold, liver mass of phospholipid and triacylglyceride increased nearly 2-fold, and relative content of monounsaturated C18:1 fatty acid increased 44% in liver phospholipids. These effects were not due to the ACBP transgene altering the protein levels of liver microsomal acyltransferase enzymes such as GPAT, lysophosphatidic acid acyltransferase (LAT), or acyl-CoA cholesterol acyltransferase 2 (ACAT-2). Thus, these data show for the first time in a physiological context that ACBP expression may play a role in LCFA-CoA metabolism.     

Correlation between microarray DNA hybridization efficiency and the position of short capture probe on the target nucleic acid

The hybridization behavior of small oligonucleotides arrayed on glass slides is currently unpredictable. In order to examine the hybridization efficiency of capture probes along target nucleic acid, 20-mer oligonucleotide probes were designed to hybridize at different distances from the 5' end of two overlapping 402- and 432-bp ermB products amplified from the target DNA. These probes were immobilized via their 5' end onto glass slides and hybridized with the two labeled products. Evaluation of the hybridization signal for each probe revealed an inverse correlation with the length of the 5' overhanging end of the captured strand and the hybridization signal intensity. Further experiments demonstrated that this phenomenon is dependent on the reassociation kinetics of the free overhanging tail of the captured DNA strand with its complementary strand. This study delineates key predictable parameters that govern the hybridization efficiency of short capture probes arrayed on glass slides. This should be most useful for designing arrays for detection of PCR products and nucleotide polymorphisms.     

A single early activation of invariant NK T cells confers long-term protection against collagen-induced arthritis in a ligand-specific manner

The glycosphingolipid alpha-galactosylceramide (alpha-GalCer) has been shown to be a potent activator of invariant NKT (iNKT) cells, rapidly inducing large amounts of both Th1 and Th2 cytokines upon injection in mice. The C-glycoside analog of alpha-GalCer (alpha-C-GalCer), by contrast, results in an enhanced Th1-type response upon activation of iNKT cells. We administered a single dose of these Ags to DBA/1 mice during the early induction phase of collagen-induced arthritis and demonstrated therapeutic efficacy of alpha-GalCer when administered early rather than late during the disease. Surprisingly, the Th1-polarizing analog alpha-C-GalCer also conferred protection. Furthermore, a biphasic role of IFN-gamma in the effect of iNKT cell stimulation was observed. Whereas in vivo neutralization of IFN-gamma release induced by either alpha-GalCer or alpha-C-GalCer early during the course of disease resulted in partial improvement of clinical arthritis symptoms, blockade of IFN-gamma release later on resulted in a more rapid onset of arthritis. Although no phenotypic changes in conventional T cells, macrophages, or APCs could be detected, important functional differences in T cell cytokine production in serum were observed upon polyclonal T cell activation, 2 wk after onset of arthritis. Whereas alpha-GalCer-treated mice produced significantly higher amounts of IL-10 upon systemic anti-CD3 stimulation compared with PBS controls, T cells from alpha-C-GalCer-treated mice, by contrast, produced substantially lower levels of cytokines, suggesting the involvement of different protective mechanisms. In conclusion, these findings suggest long-term, ligand-specific, time-dependent, and partially IFN-gamma-dependent immunomodulatory effects of iNKT cells in collagen-induced arthritis.     

Domain orientation in the inactive response regulator Mycobacterium tuberculosis MtrA provides a barrier to activation

The structure of MtrA, an essential gene product for the human pathogen Mycobacterium tuberculosis, has been solved to a resolution of 2.1 A. MtrA is a member of the OmpR/PhoB family of response regulators and represents the fourth family member for which a structure of the protein in its inactive state has been determined. As is true for all OmpR/PhoB family members, MtrA possesses an N-terminal regulatory domain and a C-terminal winged helix-turn-helix DNA-binding domain, with phosphorylation of the regulatory domain modulating the activity of the protein. In the inactive form of MtrA, these two domains form an extensive interface that is composed of the alpha4-beta5-alpha5 face of the regulatory domain and the C-terminal end of the positioning helix, the trans-activation loop, and the recognition helix of the DNA-binding domain. This domain orientation suggests a mechanism of mutual inhibition by the two domains. Activation of MtrA would require a disruption of this interface to allow the alpha4-beta5-alpha5 face of the regulatory domain to form the intermolecule interactions that are associated with the active state and to allow the recognition helix to interact with DNA. Furthermore, the interface appears to stabilize the inactive conformation of MtrA, potentially reducing the rate of phosphorylation of the N-terminal domain. This combination of effects may form a switch, regulating the activity of MtrA. The domain orientation exhibited by MtrA also provides a rationale for the variation in linker length that is observed within the OmpR/PhoB family of response regulators.     

Cophylogeny and disparate rates of evolution in sympatric lineages of chewing lice on pocket gophers

Although molecular-based phylogenetic studies of hosts and parasites are increasingly common in the literature, no study to date has examined two congeneric lineages of parasites that live in sympatry on the same lineage of hosts. This study examines phylogenetic relationships among chewing lice (Phthiraptera: Trichodectidae) of the Geomydoecus coronadoi and Geomydoecus mexicanus species complexes and compares these to phylogenetic patterns in their hosts (pocket gophers of the rodent family Geomyidae). Sympatry of congeneric lice provides a natural experiment to test the hypothesis that closely related lineages of parasites will respond similarly to the same host. Sequence data from the mitochondrial COI and the nuclear EF-1alpha genes confirm that the two louse complexes are reciprocally monophyletic and that individual clades within each species complex parasitize a different species of pocket gopher. Phylogenetic comparisons reveal that both louse complexes show a significant pattern of cophylogeny with their hosts. Comparisons of rates of nucleotide substitution at 4-fold degenerate sites in the COI gene indicate that both groups of lice have significantly higher basal mutation rates than their hosts. The two groups of lice have similar basal rates of mutation, but lice of the G. coronadoi complex show significantly elevated rates of nucleotide substitution at all sites. These rate differences are hypothesized to result from population-level phenomena, such as effective population size, founder effects, and drift, that influence rates of nucleotide substitution.     

Social structure varies with elevation in an Alpine ant

Insect societies vary greatly in social organization, yet the relative roles of ecological and genetic factors in driving this variation remain poorly understood. Identifying how social structure varies along environmental gradients can provide insights into the ecological conditions favouring alternative social organizations. Here, we investigate how queen number variation is distributed along elevation gradients within a socially polymorphic ant, the Alpine silver ant Formica selysi. We sampled low‐ and high‐elevation populations in multiple Alpine valleys. We show that populations belonging to different drainage basins are genetically differentiated. In contrast, there is little genetic divergence between low‐ and high‐elevation populations within the same drainage basin. Thus, elevation gradients in each of the drainage basins represent independent contrasts. Whatever the elevation, all well‐sampled populations are socially polymorphic, containing both monogynous (= one queen) and polygynous (= multiple queen) colonies. However, the proportion of monogynous colonies per population increases at higher elevation, while the effective number of queens in polygynous colonies decreases, and this pattern is replicated in each drainage basin. The increased prevalence of colonies with a single queen at high elevation is correlated with summer and winter average temperature, but not with precipitation. The colder, unpredictable and patchy environment encountered at higher elevations may favour larger queens with the ability to disperse and establish incipient monogynous colonies independently, while the stable and continuous habitat in the lowlands may favour large, fast‐growing polygynous colonies. By highlighting differences in the environmental conditions favouring monogynous or polygynous colonies, this study sheds light on the ecological factors influencing the distribution and maintenance of social polymorphism.     

A kinetic approach to the dependence of dissimilatory metal reduction by Shewanella oneidensis MR-1 on the outer membrane cytochromes c OmcA and OmcB

The Gram-negative bacterium Shewanella oneidensis MR-1 shows a remarkably versatile anaerobic respiratory metabolism. One of its hallmarks is its ability to grow and survive through the reduction of metallic compounds. Among other proteins, outer membrane decaheme cytochromes c OmcA and OmcB have been identified as key players in metal reduction. In fact, both of these cytochromes have been proposed to be terminal Fe(III) and Mn(IV) reductases, although their role in the reduction of other metals is less well understood. To obtain more insight into this, we constructed and analyzed omcA, omcB and omcA/omcB insertion mutants of S. oneidensis MR-1. Anaerobic growth on Fe(III), V(V), Se(VI) and U(VI) revealed a requirement for both OmcA and OmcB in Fe(III) reduction, a redundant function in V(V) reduction, and no apparent involvement in Se(VI) and U(VI) reduction. Growth of the omcB(-) mutant on Fe(III) was more affected than growth of the omcA(-) mutant, suggesting OmcB to be the principal Fe(III) reductase. This result was corroborated through the examination of whole cell kinetics of OmcA- and OmcB-dependent Fe(III)-nitrilotriacetic acid reduction, showing that OmcB is approximately 11.5 and approximately 6.3 times faster than OmcA at saturating and low nonsaturating concentrations of Fe(III)-nitrilotriacetic acid, respectively, whereas the omcA(-) omcB(-) double mutant was devoid of Fe(III)-nitrilotriacetic acid reduction activity. These experiments reveal, for the first time, that OmcA and OmcB are the sole terminal Fe(III) reductases present in S. oneidensis MR-1. Kinetic inhibition experiments further revealed vanadate (V(2)O(5)) to be a competitive and mixed-type inhibitor of OmcA and OmcB, respectively, showing similar affinities relative to Fe(III)-nitrilotriacetic acid. Neither sodium selenate nor uranyl acetate were found to inhibit OmcA- and OmcB-dependent Fe(III)-nitrilotriacetic acid reduction. Taken together with our growth experiments, this suggests that proteins other than OmcA and OmcB play key roles in anaerobic Se(VI) and U(VI) respiration.     

Novel function of transcription factor Nrf2 as an inhibitor of RON tyrosine kinase receptor-mediated cancer cell invasion

Recepteur d' origine nantais (RON), a tyrosine kinase receptor, is aberrantly expressed in human tumors and promotes cancer cell invasion. RON receptor activation is also associated with resistance to tamoxifen treatment in breast cancer cells. Nrf2 is a positive regulator of cytoprotective genes. Using chromatin immunoprecipitation (ChIP) and site-directed mutagenesis studies of the RON promoter, we identified Nrf2 as a negative regulator of RON gene expression. High Nrf2 and low RON expression was observed in normal mammary tissue whereas high RON and low or undetectable expression of Nrf2 was observed in breast tumors. The Nrf2 inducer sulforaphane (SFN) as well as ectopic Nrf2 expression or knock-down of the Nrf2 negative regulator keap1, which stabilizes Nrf2, inhibited RON expression and invasion of carcinoma cells. Consequently, our studies identified a novel functional role for Nrf2 as a "repressor" and RON kinase as a molecular target of SFN, which mediates the anti-tumor effects of SFN. These results are not limited to breast cancer cells since the Nrf2 inducer SFN stabilized Nrf2 and inhibited RON expression in carcinoma cells from various tumor types.     

Narratives of success among Irish and African Caribbean migrants

This paper compares the narratives of two men in midlife who migrated to the UK from Ireland and from the Caribbean as children, in the middle of the last century. We examine how success is narrated over the life course to show how migrants’ positioning of themselves differs from the ways in which they are positioned by outsiders, including in policy and public discourse. We conclude that while outsider narratives often polarise success and failure, insider understandings of success are dynamic and culturally and historically situated.