Role of the INK4a locus in tumor suppression and cell mortality

The cell cycle inhibitor p16INK4a is inactivated in many human tumors and in families with hereditary melanoma and pancreatic cancer. Tumor-associated alterations in the INK4a locus may also affect the overlapping gene encoding p19ARF and the adjacent gene encoding p15I1NK4b, both negative regulators of cell proliferation. We report the phenotype of mice carrying a targeted deletion of the INK4a locus that eliminates both p16INK4a and p19ARF. The mice are viable but develop spontaneous tumors at an early age and are highly sensitive to carcinogenic treatments. INK4a-deficient primary fibroblasts proliferate rapidly and have a high colony-formation efficiency. In contrast with normal cells, the introduction of activated Ha-ras into INK4a-deficient fibroblasts can result in neoplastic transformation. These findings directly demonstrate that the INK4a locus functions to suppress neoplastic growth.

NPHS2, encoding the glomerular protein podocin, is mutated in autosomal recessive steroid-resistant nephrotic syndrome

Familial idiopathic nephrotic syndromes represent a heterogeneous group of kidney disorders, and include autosomal recessive steroid-resistant nephrotic syndrome, which is characterized by early childhood onset of proteinuria, rapid progression to end-stage renal disease and focal segmental glomerulosclerosis. A causative gene for this disease, NPHS2, was mapped to 1q25-31 and we report here its identification by positional cloning. NPHS2 is almost exclusively expressed in the podocytes of fetal and mature kidney glomeruli, and encodes a new integral membrane protein, podocin, belonging to the stomatin protein family. We found ten different NPHS2 mutations, comprising nonsense, frameshift and missense mutations, to segregate with the disease, demonstrating a crucial role for podocin in the function of the glomerular filtration barrier.

Complete genome sequence of Methanobacterium thermoautotrophicum deltaH: functional analysis and comparative genomics

The complete 1,751,377-bp sequence of the genome of the thermophilic archaeon Methanobacterium thermoautotrophicum deltaH has been determined by a whole-genome shotgun sequencing approach. A total of 1,855 open reading frames (ORFs) have been identified that appear to encode polypeptides, 844 (46%) of which have been assigned putative functions based on their similarities to database sequences with assigned functions. A total of 514 (28%) of the ORF-encoded polypeptides are related to sequences with unknown functions, and 496 (27%) have little or no homology to sequences in public databases. Comparisons with Eucarya-, Bacteria-, and Archaea-specific databases reveal that 1,013 of the putative gene products (54%) are most similar to polypeptide sequences described previously for other organisms in the domain Archaea. Comparisons with the Methanococcus jannaschii genome data underline the extensive divergence that has occurred between these two methanogens; only 352 (19%) of M. thermoautotrophicum ORFs encode sequences that are >50% identical to M. jannaschii polypeptides, and there is little conservation in the relative locations of orthologous genes. When the M. thermoautotrophicum ORFs are compared to sequences from only the eucaryal and bacterial domains, 786 (42%) are more similar to bacterial sequences and 241 (13%) are more similar to eucaryal sequences. The bacterial domain-like gene products include the majority of those predicted to be involved in cofactor and small molecule biosyntheses, intermediary metabolism, transport, nitrogen fixation, regulatory functions, and interactions with the environment. Most proteins predicted to be involved in DNA metabolism, transcription, and translation are more similar to eucaryal sequences. Gene structure and organization have features that are typical of the Bacteria, including genes that encode polypeptides closely related to eucaryal proteins. There are 24 polypeptides that could form two-component sensor kinase-response regulator systems and homologs of the bacterial Hsp70-response proteins DnaK and DnaJ, which are notably absent in M. jannaschii. DNA replication initiation and chromosome packaging in M. thermoautotrophicum are predicted to have eucaryal features, based on the presence of two Cdc6 homologs and three histones; however, the presence of an ftsZ gene indicates a bacterial type of cell division initiation. The DNA polymerases include an X-family repair type and an unusual archaeal B type formed by two separate polypeptides. The DNA-dependent RNA polymerase (RNAP) subunits A', A", B', B" and H are encoded in a typical archaeal RNAP operon, although a second A' subunit-encoding gene is present at a remote location. There are two rRNA operons, and 39 tRNA genes are dispersed around the genome, although most of these occur in clusters. Three of the tRNA genes have introns, including the tRNAPro (GGG) gene, which contains a second intron at an unprecedented location. There is no selenocysteinyl-tRNA gene nor evidence for classically organized IS elements, prophages, or plasmids. The genome contains one intein and two extended repeats (3.6 and 8.6 kb) that are members of a family with 18 representatives in the M. jannaschii genome.

The translation initiation factor eIF-4E binds to a common motif shared by the translation factor eIF-4 gamma and the translational repressors 4E-binding proteins

Eukaryotic translation initiation factor 4E (eIF-4E), which possesses cap-binding activity, functions in the recruitment of mRNA to polysomes as part of a three-subunit complex, eIF-4F (cap-binding complex). eIF-4E is the least abundant of all translation initiation factors and a target of growth regulatory pathways. Recently, two human cDNAs encoding novel eIF-4E-binding proteins (4E-BPs) which function as repressors of cap-dependent translation have been cloned. Their interaction with eIF-4E is negatively regulated by phosphorylation in response to cell treatment with insulin or growth factors. The present study aimed to characterize the molecular interactions between eIF-4E and the other subunits of eIF-4F and to similarly characterize the molecular interactions between eIF-4E and the 4E-BPs. A 49-amino-acid region of eIF-4 gamma, located in the N-terminal side of the site of cleavage by Picornaviridae protease 2A, was found to be sufficient for interacting with eIF-4E. Analysis of deletion mutants in this region led to the identification of a 12-amino-acid sequence conserved between mammals and Saccharomyces cerevisiae that is critical for the interaction with eIF-4E. A similar motif is found in the amino acid sequence of the 4E-BPs, and point mutations in this motif abolish the interaction with eIF-4E. These results shed light on the mechanisms of eIF-4F assembly and on the translational regulation by insulin and growth factors.

College binge drinking in the 1990s: a continuing problem. Results of the Harvard School of Public Health 1999 College Alcohol Study

In 1999, the Harvard School of Public Health College Alcohol Study resurveyed colleges that participated in the 1993 and 1997 surveys. Responses to mail questionnaires from more than 14,000 students at 119 nationally representative 4-year colleges in 39 states were compared with responses received in 1997 and 1993. Two of 5 students (44%) were binge drinkers in 1999, the same rate as in 1993. However, both abstention and frequent binge-drinking rates increased significantly. In 1999, 19% were abstainers, and 23% were frequent binge drinkers. As before, binge drinkers, and particularly frequent binge drinkers, were more likely than other students to experience alcohol-related problems. At colleges with high binge-drinking rates, students who did not binge drink continued to be at higher risk of encountering the second-hand effects of others' heavy drinking. The continuing high level of binge drinking is discussed in the context of the heightened attention and increased actions at colleges. Although it may take more time for interventions to take effect, the actions college health providers have undertaken thus far may not be a sufficient response.

The AGAMOUS-LIKE 20 MADS domain protein integrates floral inductive pathways in Arabidopsis

The very late-flowering behavior of Arabidopsis winter-annual ecotypes is conferred mainly by two genes, FRIGIDA (FRI) and FLOWERING LOCUS C (FLC). A MADS-domain gene, AGAMOUS-LIKE 20 (AGL20), was identified as a dominant FRI suppressor in activation tagging mutagenesis. Overexpression of AGL20 suppresses not only the late flowering of plants that have functional FRI and FLC alleles but also the delayed phase transitions during the vegetative stages of plant development. Interestingly, AGL20 expression is positively regulated not only by the redundant vernalization and autonomous pathways of flowering but also by the photoperiod pathway. Our results indicate that AGL20 is an important integrator of three pathways controlling flowering in Arabidopsis.

Involvement of Brca2 in DNA repair

Abnormalities precipitated by a targeted truncation in the murine gene Brca2 define its involvement in DNA repair. In culture, cells harboring truncated Brca2 exhibit a proliferative impediment that worsens with successive passages. Arrest in the G1 and G2/M phases is accompanied by elevated p53 and p21 expression. Increased sensitivity to genotoxic agents, particularly ultraviolet light and methylmethanesulfonate, shows that Brca2 function is essential for the ability to survive DNA damage. But checkpoint activation and apoptotic mechanisms are largely unaffected, thereby implicating Brca2 in repair. This is substantiated by the spontaneous accumulation of chromosomal abnormalities, including breaks and aberrant chromatid exchanges. These findings define a function of Brca2 in DNA repair, whose loss precipitates replicative failure, mutagen sensitivity, and genetic instability reminiscent of Bloom syndrome and Fanconi anemia.

Extent of microstructural white matter injury in postconcussive syndrome correlates with impaired cognitive reaction time: a 3T diffusion tensor imaging study of mild traumatic brain injury

BACKGROUND AND PURPOSE

Diffusion tensor imaging (DTI) may be a useful index of microstructural changes implicated in diffuse axonal injury (DAI) linked to persistent postconcussive symptoms, especially in mild traumatic brain injury (TBI), for which conventional MR imaging techniques may lack sensitivity. We hypothesized that for mild TBI, DTI measures of DAI would correlate with impairments in reaction time, whereas the number of focal lesions on conventional 3T MR imaging would not.

MATERIALS AND METHODS

Thirty-four adult patients with mild TBI with persistent symptoms were assessed for DAI by quantifying traumatic microhemorrhages detected on a conventional set of T2*-weighted gradient-echo images and by DTI measures of fractional anisotropy (FA) within a set of a priori regions of interest. FA values 2.5 SDs below the region average, based on a group of 26 healthy control adults, were coded as exhibiting DAI.

RESULTS

DTI measures revealed several predominant regions of damage including the anterior corona radiata (41% of the patients), uncinate fasciculus (29%), genu of the corpus callosum (21%), inferior longitudinal fasciculus (21%), and cingulum bundle (18%). The number of damaged white matter structures as quantified by DTI was significantly correlated with mean reaction time on a simple cognitive task (r = 0.49, P = .012). In contradistinction, the number of traumatic microhemorrhages was uncorrelated with reaction time (r = -0.08, P = .71).

CONCLUSION

Microstructural white matter lesions detected by DTI correlate with persistent cognitive deficits in mild TBI, even in populations in which conventional measures do not. DTI measures may thus contribute additional diagnostic information related to DAI.

Quinoline as a privileged scaffold in cancer drug discovery

Quinoline (1-azanaphthalene) is a heterocyclic aromatic nitrogen compound characterized by a double-ring structure that contains a benzene ring fused to pyridine at two adjacent carbon atoms. Quinoline compounds are widely used as "parental" compounds to synthesize molecules with medical benefits, especially with anti-malarial and anti-microbial activities. Certain quinoline-based compounds also show effective anticancer activity. This broad spectrum of biological and biochemical activities has been further facilitated by the synthetic versatility of quinoline, which allows the generation of a large number of structurally diverse derivatives. This includes numerous analogues derived from substitution of the quinoline ring system, and derivatization of quinoline ring structure. Quinoline and its analogs have recently been examined for their modes of function in the inhibition of tyrosine kinases, proteasome, tubulin polymerization and DNA repair. In this review, we have summarized our knowledge on quinoline compounds with respect to their anticancer activities, mechanisms of action, structure-activity relationship (SAR), and selective and specific activity against various cancer drug targets. In particular, we focus our review on in vitro and in vivo anticancer activities of quinoline and its analogs in the context of cancer drug development and refinement.

La autoantigen enhances and corrects aberrant translation of poliovirus RNA in reticulocyte lysate

Translation initiation on poliovirus RNA occurs by internal binding of ribosomes to a sequence within the 5' untranslated region. We have previously characterized a HeLa cell protein, p52, that binds to a fragment of the poliovirus 5' untranslated region (K. Meerovitch, J. Pelletier, and N. Sonenberg, Genes Dev. 3:1026-1034, 1989). Here we report the purification of the HeLa p52. Protein microsequencing identified p52 as La autoantigen. The La protein is a human antigen that is recognized by antibodies from patients with autoimmune disorders such as systemic lupus erythematosus and Sjögren's syndrome. We show that the La protein stimulates translation of poliovirus RNA, but not brome mosaic virus, tobacco mosaic virus, and alfalfa mosaic virus 4 RNA, translation in a reticulocyte lysate. In addition, La corrects aberrant translation of poliovirus RNA in a reticulocyte lysate. Subcellular immunolocalization showed that La protein is mainly nuclear, but after poliovirus infection, La is redistributed to the cytoplasm. Our results suggest that La protein is involved in poliovirus internal initiation of translation and might function through a similar mechanism in the translation of cellular mRNAs.

Spatial patterns in the distribution of tropical tree species

Fully mapped tree census plots of large area, 25 to 52 hectares, have now been completed at six different sites in tropical forests, including dry deciduous to wet evergreen forest on two continents. One of the main goals of these plots has been to evaluate spatial patterns in tropical tree populations. Here the degree of aggregation in the distribution of 1768 tree species is examined based on the average density of conspecific trees in circular neighborhoods around each tree. When all individuals larger than 1 centimeter in stem diameter were included, nearly every species was more aggregated than a random distribution. Considering only larger trees (>/= 10 centimeters in diameter), the pattern persisted, with most species being more aggregated than random. Rare species were more aggregated than common species. All six forests were very similar in all the particulars of these results.

Changes in binge drinking and related problems among American college students between 1993 and 1997. Results of the Harvard School of Public Health College Alcohol Study

In 1997, the Harvard School of Public Health College Alcohol Study resurveyed colleges that participated in a 1993 study. The findings revealed little change in binge drinking: a slight decrease in percentage of binge drinkers and slight increases in percentages of abstainers and frequent binge drinkers. Two of 5 students were binge drinkers (42.7%); 1 in 5 (19.0%) was an abstainer, and 1 in 5 was a frequent binge drinker (20.7%). As was true in 1993, 4 of 5 residents of fraternities or sororities were binge drinkers (81.1%). Asian students showed a greater increase and White students a greater decrease in binge drinking from 1993 to 1997, compared with all other students. Among students who drank alcohol, increases in frequency of drinking; drunkenness; drinking to get drunk; and alcohol-related problems, including drinking and driving, were reported. Binge drinkers in both 1993 and 1997 were at increased risk of alcohol-related problems, and nonbingers at colleges with high binge drinking rates had increased risks of encountering secondhand effects of binge drinking.

Missense mutations in desmin associated with familial cardiac and skeletal myopathy

Desmin-related myopathy (OMIM 601419) is a familial disorder characterized by skeletal muscle weakness associated with cardiac conduction blocks, arrhythmias and restrictive heart failure, and by intracytoplasmic accumulation of desmin-reactive deposits in cardiac and skeletal muscle cells. The underlying molecular mechanisms are unknown. Involvement of the desmin gene (DES) has been excluded in three families diagnosed with desmin-related myopathy. We report two new families with desmin-related cardioskeletal myopathy associated with mutations in the highly conserved carboxy-terminal end of the desmin rod domain. A heterozygous A337P mutation was identified in a family with an adult-onset skeletal myopathy and mild cardiac involvement. Compound heterozygosity for two other mutations, A360P and N393I, was detected in a second family characterized by childhood-onset aggressive course of cardiac and skeletal myopathy.

Attenuation of apoptosis underlies B lymphocyte stimulator enhancement of humoral immune response

B lymphocyte stimulator (BLyS) is a newly identified monocyte-specific TNF family cytokine. It has been implicated in the development of autoimmunity, and functions as a potent costimulator with antiimmunoglobulin M in B cell proliferation in vitro. Here we demonstrate that BLyS prominently enhances the humoral responses to both T cell-independent and T cell-dependent antigens, primarily by attenuation of apoptosis as evidenced by the prolonged survival of antigen-activated B cells in vivo and in vitro. BLyS acts on primary splenic B cells autonomously, and directly cooperates with CD40 ligand (CD40L) in B cell activation in vitro by protecting replicating B cells from apoptosis. Moreover, although BLyS alone cannot activate the cell cycle, it is sufficient to prolong the survival of naive resting B cells in vitro. Attenuation of apoptosis by BLyS correlates with changes in the ratios between Bcl-2 family proteins in favor of cell survival, predominantly by reducing the proapoptotic Bak and increasing its prosurvival partners, Bcl-2 and Bcl-xL. In either resting or CD40L-activated B cells, the NF-kappaB transcription factors RelB and p50 are specifically activated, suggesting that they may mediate BLyS signals for B cell survival. Together, these results provide direct evidence for BLyS enhancement of both T cell-independent and T cell-dependent humoral immune responses, and imply a role for BLyS in the conservation of the B cell repertoire. The ability of BLyS to increase B cell survival indiscriminately, at either a resting or activated state, and to cooperate with CD40L, further suggests that attenuation of apoptosis underlies BLyS enhancement of polyclonal autoimmunity as well as the physiologic humoral immune response.

High rate of HTLV-II infection in seropositive i.v. drug abusers in New Orleans

Confirmed infection with HTLV-II (human T cell leukemia virus type II) has been described only in rare cases. The major limitation to serological diagnosis of HTLV-II has been the difficulty of distinguishing HTLV-II from HTLV-I (human T cell leukemia virus type I) infection, because of substantial cross-reactivity between the viruses. A sensitive modification of the polymerase chain reaction method was used to provide unambiguous molecular evidence that a significant proportion of intravenous drug abusers are infected with HTLV, and the majority of these individuals are infected with HTLV-II rather than HTLV-I. Of 23 individuals confirmed by polymerase chain reaction analysis to be infected with HTLV, 21 were identified to be infected with HTLV-II, and 2 were infected with HTLV-I. Molecular identification of an HTLV-II--infected population provides an opportunity to investigate the pathogenicity of HTLV-II in humans.

Astrocytes accumulate A beta 42 and give rise to astrocytic amyloid plaques in Alzheimer disease brains

beta-Amyloid(1-42) (A beta 42), a major component of amyloid plaques, accumulates within pyramidal neurons in the brains of individuals with Alzheimer's disease (AD) and Down syndrome. In brain areas exhibiting AD pathology, A beta 42-immunopositive material is observed in astrocytes. In the present study, single- and double-label immunohistochemistry were used to reveal the origin and fate of this material in astrocytes. Our findings suggest that astrocytes throughout the entorhinal cortex of AD patients gradually accumulate A beta 42-positive material and that the amount of this material correlates positively with the extent of local AD pathology. A beta 42-positive material within astrocytes appears to be of neuronal origin, most likely accumulated via phagocytosis of local degenerated dendrites and synapses, especially in the cortical molecular layer. The co-localization of neuron-specific proteins, alpha 7 nicotinic acetylcholine receptor and choline acetyltransferase, in A beta 42-burdened, activated astrocytes supports this possibility. Our results also suggest that some astrocytes containing A beta 42-positive deposits undergo lysis, resulting in the formation of astrocyte-derived amyloid plaques in the cortical molecular layer in brain regions showing moderate to advanced AD pathology. These astrocytic plaques can be distinguished from those arising from neuronal lysis by virtue of their smaller size, their nearly exclusive localization in the subpial portion of the molecular layer of the cerebrocortex, and by their intense glial fibrillary acidic protein immunoreactivity. Overall, A beta 42 accumulation and the selective lysis of A beta 42-burdened neurons and astrocytes appear to make a major contribution to the observed amyloid plaques in AD brains.

FIERY1 encoding an inositol polyphosphate 1-phosphatase is a negative regulator of abscisic acid and stress signaling in Arabidopsis

The plant hormone abscisic acid (ABA) plays a wide range of important roles in plant growth and development, including embryogenesis, seed dormancy, root and shoot growth, transpiration, and stress tolerance. ABA and various abiotic stresses also activate the expression of numerous plant genes through undefined signaling pathways. To gain insight into ABA and stress signal transduction, we conducted a genetic screen based on ABA- and stress-inducible gene transcription. Here we report the identification of an Arabidopsis mutation, fiery1 (fry1), which results in super-induction of ABA- and stress-responsive genes. Seed germination and postembryonic development of fry1 are more sensitive to ABA or stress inhibition. The mutant plants are also compromised in tolerance to freezing, drought, and salt stresses. Map-based cloning revealed that FRY1 encodes an inositol polyphosphate 1-phosphatase, which functions in the catabolism of inositol 1, 4, 5-trisphosphate (IP(3)). Upon ABA treatment, fry1 mutant plants accumulated more IP(3) than did the wild-type plants. These results provide the first genetic evidence indicating that phosphoinositols mediate ABA and stress signal transduction in plants and their turnover is critical for attenuating ABA and stress signaling.

CDK inhibitors p18(INK4c) and p27(Kip1) mediate two separate pathways to collaboratively suppress pituitary tumorigenesis

INK4 and CIP/KIP are two distinct families of cyclin-dependent kinase (CDK) inhibitors implicated in mediating a wide range of cell growth control signals. We have created p18(INK4c)-deficient mice. These mice develop gigantism and widespread organomegaly. The pituitary gland, spleen, and thymus are disproportionately enlarged and hyperplastic. T and B lymphocytes develop normally in p18-deficient mice, but both exhibit increased cellularity and a higher proliferative rate upon mitogenic stimulation. Loss of p18, like that of p27, but not other CDK inhibitor genes, leads to a gradual progression from intermediate lobe pituitary hyperplasia in young mice to an adenoma by 10 months of age with a nearly complete penetrance. Mice lacking both p18 and p27, like mice chimeric for Rb deficiency, invariably died from pituitary adenomas by 3 months. Hence, p18 and p27 mediate two separate pathways to collaboratively suppress pituitary tumorigenesis, likely by controlling the function of Rb.

The Arabidopsis HOS1 gene negatively regulates cold signal transduction and encodes a RING finger protein that displays cold-regulated nucleo--cytoplasmic partitioning

Low temperature is one of the most important environmental stimuli that control gene transcription programs and development in plants. In Arabidopsis thaliana, the HOS1 locus is a key negative regulator of low temperature-responsive gene transcription. The recessive hos1 mutation causes enhanced induction of the CBF transcription factors by low temperature as well as of their downstream cold-responsive genes. The hos1 mutant plants flower early, and this correlates with a low level of Flowering Locus C gene expression. The HOS1 gene was isolated through positional cloning. HOS1 encodes a novel protein with a RING finger motif near the amino terminus. HOS1 is ubiquitously expressed in all plant tissues. HOS1--GFP translational fusion studies reveal that HOS1 protein resides in the cytoplasm at normal growth temperatures. However, in response to low temperature treatments, HOS1 accumulates in the nucleus. Ectopic expression of HOS1 in wild-type plants causes cosuppression of HOS1 expression and mimics the hos1 mutant phenotypes.

Desmin myopathy, a skeletal myopathy with cardiomyopathy caused by mutations in the desmin gene

BACKGROUND

Myofibrillar myopathies, often referred to as desmin-related myopathies, are a heterogeneous group of inherited or sporadic distal-onset skeletal myopathies associated with cardiomyopathy. Among the myofibrillar proteins that characteristically accumulate within the muscle fibers of affected patients, the one found most consistently is desmin, a muscle-specific intermediate-filament protein responsible for the structural integrity of the myofibrils. Skeletal and cardiac myopathy develops in mice that lack desmin, suggesting that mutations in the desmin gene may be pathogenic.

METHODS

We examined 22 patients from 8 families with dominantly inherited myofibrillar or desmin-related myopathy and 2 patients with sporadic disease and analyzed the desmin gene for mutations, using complementary DNA (cDNA) amplified from muscle-biopsy specimens and genomic DNA extracted from blood lymphocytes. Restriction-enzyme analysis was used to confirm the mutations. Expression vectors containing normal or mutant desmin cDNA were introduced into cultured cells to determine whether the mutant desmin formed intermediate filaments.

RESULTS

Six missense mutations in the coding region of the desmin gene that cause the substitution of an amino acid were identified in 11 patients (10 members of 4 families and 1 patient with sporadic disease); a splicing defect that resulted in the deletion of exon 3 was identified in the other patient with sporadic disease. Mutations were clustered in the carboxy-terminal part of the rod domain, which is critical for filament assembly. In transfected cells, the mutant desmin was unable to form a filamentous network. Seven of the 12 patients with mutations in the desmin gene had cardiomyopathy.

CONCLUSIONS

Mutations in the desmin gene affecting intermediate filaments cause a distinct myopathy that is often associated with cardiomyopathy and is termed "desmin myopathy." The mutant desmin interferes with the normal assembly of intermediate filaments, resulting in fragility of the myofibrils and severe dysfunction of skeletal and cardiac muscles.

Effect of selected environmental and physico-chemical factors on bacterial cytoplasmic membranes

Membranes lipids are one of the most adaptable molecules in response to perturbations. Even subtle changes of the composition of acyl chains or head groups can alter the packing arrangements of lipids within the bilayer. This changes the balance between bilayer and nonbilayer lipids, serving to affect bilayer stability and fluidity, as well as altering lipid-protein interactions. External factors can also change membrane fluidity and lipid composition; including temperature, chemicals, ions, pressure, nutrients and the growth phase of the microbial culture. Various biophysical techniques have been used to monitor fluidity changes within the bacterial membrane. In this review, bacterial cytoplasmic membrane changes and related functional effects will be examined as well as the use of fluorescence polarization methods and examples of data obtained from research with bacteria.

Local structural elements in the mostly unstructured transcriptional activation domain of human p53

DNA transcription is initiated by a small regulatory region of transactivators known as the transactivation domain. In contrast to the rapid progress made on the functional aspect of this promiscuous domain, its structural feature is still poorly characterized. Here, our multidimensional NMR study reveals that an unbound full-length p53 transactivation domain, although similar to the recently discovered group of loosely folded proteins in that it does not have tertiary structure, is nevertheless populated by an amphipathic helix and two nascent turns. The helix is formed by residues Thr(18)-Leu(26) (Thr-Phe-Ser-Asp-Leu-Trp-Lys-Leu-Leu), whereas the two turns are formed by residues Met(40)-Met(44) and Asp(48)-Trp(53), respectively. It is remarkable that these local secondary structures are selectively formed by functionally critical and positionally conserved hydrophobic residues present in several acidic transactivation domains. This observation suggests that such local structures are general features of acidic transactivation domains and may represent "specificity determinants" (Ptashne, M., and Gann, A. A. F. (1997), Nature 386, 569-577) that are important for transcriptional activity.

Phase locking of single neuron activity to theta oscillations during working memory in monkey extrastriate visual cortex

Working memory has been linked to elevated single neuron discharge in monkeys and to oscillatory changes in the human EEG, but the relation between these effects has remained largely unexplored. We addressed this question by measuring local field potentials and single unit activity simultaneously from multiple electrodes placed in extrastriate visual cortex while monkeys were performing a working memory task. We describe a significant enhancement in theta band energy during the delay period. Theta oscillations had a systematic effect on single neuron activity, with neurons emitting more action potentials near their preferred angle of each theta cycle. Sample-selective delay activity was enhanced if only action potentials emitted near the preferred theta angle were considered. Our results suggest that extrastriate visual cortex is involved in short-term maintenance of information and that theta oscillations provide a mechanism for structuring the recurrent interaction between neurons in different brain regions that underlie working memory.

The lipopolysaccharide-activated toll-like receptor (TLR)-4 induces synthesis of the closely related receptor TLR-2 in adipocytes

The central regulatory role of the adipocyte in whole body energy homeostasis is well established. However, recent findings suggest that preadipocytes and adipocytes may play an important physiological role in the regulation of both the innate and adaptive immune response. To systematically characterize the molecular machinery of the adipocyte that mediates the recognition of pathogens, we have focused our analysis on the recently identified Toll-like receptors (TLRs). These receptors have been implicated as mediators of the cellular response to bacterial lipopolysacharides (LPSs). Here, we report the cloning and functional characterization of mouse TLR-2 from 3T3-L1 adipocytes. TLR-2 synthesis is strongly induced in the adipocyte by LPS, TNFalpha, and the yeast cell wall extract zymosan. TLR-2 undergoes a lengthy intracellular maturation process with a half-life of exit from the ER of approximately 3 h. Furthermore, LPS treatment of adipocytes results in dramatic changes at the level of gene expression, including the synthesis of a distinct set of secretory proteins such as interleukin-6. Our studies demonstrate the presence of a fully intact pathway of innate immunity in the adipocyte that can be activated by LPS binding to the cell surface and results in the secretion of immunomodulatory molecules.