The trithorax group gene osa encodes an ARID-domain protein that genetically interacts with the brahma chromatin-remodeling factor to regulate transcription

The trithorax group gene brahma (brm) encodes the ATPase subunit of a chromatin-remodeling complex involved in homeotic gene regulation. We report here that brm interacts with another trithorax group gene, osa, to regulate the expression of the Antennapedia P2 promoter. Regulation of Antennapedia by BRM and OSA proteins requires sequences 5' to the P2 promoter. Loss of maternal osa function causes severe segmentation defects, indicating that the function of osa is not limited to homeotic gene regulation. The OSA protein contains an ARID domain, a DNA-binding domain also present in the yeast SWI1 and Drosophila DRI proteins. We propose that the OSA protein may target the BRM complex to Antennapedia and other regulated genes.     

Declining sperm counts in the United States? A critical review

PURPOSE: Recent reports suggest declining sperm counts in the United States. These reports did not include all available data and did not account for geographic variations noted in prior studies. We examined all available data on U.S. sperm counts and evaluated whether geographic variations account for the decline suggested. MATERIALS AND METHODS: We reviewed all 29 U.S. studies from 1938 to 1996 reporting manually counted semen analyses of 9,612 fertile or presumably fertile men. We determined mean sperm concentrations by geographic location with weighted analysis of variance, and assessed any changes with time by linear regression analysis. RESULTS: Mean sperm concentrations from New York were significantly higher than from all other U.S. cities (98.6 versus 71.6 x 10(6) sperm per cc, respectively, p = 0.006). There has been no statistically significant change with time for mean sperm concentrations reported from New York (p = 0.49) or from U.S. cities other than New York (p = 0.62). Analysis without separating by location revealed a decline (p = 0.047). CONCLUSIONS: Sperm concentrations are highest in New York compared to other U.S. cities. When accounting for this geographic difference and examining all available data, there appears to be no significant change in sperm counts in the U.S. during the last 60 years. Further studies addressing the causes of geographic variations are needed.     

Lack of infection in HIV-exposed individuals is associated with a strong CD8(+) cell noncytotoxic anti-HIV response

Individuals repeatedly exposed to HIV, but who remain uninfected, form a population enriched for persons likely to have either natural or acquired resistance to the virus. We have studied four such exposed uninfected cohorts, representing 60 individuals, for evidence of protective immunity. This population included participants exposed to HIV through anal or vaginal receptive intercourse on multiple occasions over many years. We observed CD8(+)-cell noncytotoxic inhibition of HIV replication in acutely infected CD4(+) cells in the vast majority of individuals most recently exposed to the virus (within 1 year). The levels of this CD8(+)-cell response were sufficient to inhibit the in vitro infection of the exposed subjects' peripheral blood mononuclear cells. We found no evidence of a significant role for CCR5 Delta32 mutation in this population, nor did CD4(+) cell susceptibility to infection or HIV-specific cytotoxic T-lymphocytes correlate with resistance to infection in the individuals tested. Therefore, the observed strong noncytotoxic CD8(+)-cell anti-HIV responses may be an antiviral immune activity contributing to the apparent protection from infection in these exposed uninfected individuals.     

The product of the cph oncogene is a truncated, nucleotide-binding protein that enhances cellular survival to stress

Cph was isolated from neoplastic Syrian hamster embryo fibroblasts initiated by 3-methylcholanthrene (MCA), and was shown to be a single copy gene in the hamster genome, conserved from yeast to human cells, expressed in fetal cells and most adult tissues, and acting synergistically with H-ras in the transformation of murine NIH3T3 fibroblasts. We have now isolated Syrian hamster full-length cDNAs for the cph oncogene and proto-oncogene. Nucleotide sequence analysis revealed that cph was activated in MCA-treated cells by a point-mutational deletion at codon 214, which caused a shift in the normal open reading frame (ORF) and brought a translation termination codon 33 amino acids downstream. While proto-cph encodes a protein (pcph) of 469 amino acids, cph encodes a truncated protein (cph) of 246 amino acids with a new, hydrophobic C-terminus. Similar mechanisms activated cph in other MCA-treated Syrian hamster cells. The cph and proto-cph proteins have partial sequence homology with two protein families: GDP/GTP exchange factors and nucleotide phosphohydrolases. In vitro translated, gel-purified cph proteins did not catalyze nucleotide exchange for H-ras, but were able to bind nucleotide phosphates, in particular ribonucleotide diphosphates such as UDP and GDP. Steady-state levels of cph mRNA increased 6.7-fold in hamster neoplastic cells, relative to a 2.2-fold increase in normal cells, when they were subjected to a nutritional stress such as serum deprivation. Moreover, cph-transformed NIH3T3 cells showed increased survival to various forms of stress (serum starvation, hyperthermia, ionizing radiation), strongly suggesting that cph participates in cellular mechanisms of response to stress.     

Localization of human transcription factor TEF-4 and TEF-5 (TEAD2, TEAD3) genes to chromosomes 19q13.3 and 6p21.2 using fluorescence in situ hybridization and radiation hybrid analysis

The tetrapeptide Ala-lle-Gly-Met bound to a Wang resin via the methionine residue was studied by NMR under MAS conditions and compared to the same peptide in solution. The bound peptide exhibits average linewidths superior to those observed for the peptide in solution. The origin of the residual NMR linewidth observed for the bound form was investigated. The dynamics of the peptide is shown to be only marginally responsible for the increased linewidth; the major cause of the line broadening appears to be nonaveraged magnetic susceptibility differences.     

Folding mechanism of the alpha-subunit of tryptophan synthase, an alpha/beta barrel protein: global analysis highlights the interconversion of multiple native, intermediate, and unfolded forms through parallel channels

A variety of techniques have been used to investigate the urea-induced kinetic folding mechanism of the alpha-subunit of tryptophan synthase from Escherichia coli. A distinctive property of this 29 kDa alpha/beta barrel protein is the presence of two stable equilibrium intermediates, populated at approximately 3 and 5 M urea. The refolding process displays multiple kinetic phases whose lifetimes span the submillisecond to greater than 100 s time scale; unfolding studies yield two relaxation times on the order of 10-100 s. In an effort to understand the populations and structural properties of both the stable and transient intermediates, stopped-flow, manual-mixing, and equilibrium circular dichroism data were globally fit to various kinetic models. Refolding and unfolding experiments from various initial urea concentrations as well as forward and reverse double-jump experiments were critical for model discrimination. The simplest kinetic model that is consistent with all of the available data involves four slowly interconverting unfolded forms that collapse within 5 ms to a marginally stable intermediate with significant secondary structure. This early intermediate is an off-pathway species that must unfold to populate a set of four on-pathway intermediates that correspond to the 3 M urea equilibrium intermediate. Reequilibrations among these conformers act as rate-limiting steps in folding for a majority of the population. A fraction of the native conformation appears in less than 1 s at 25 degrees C, demonstrating that even large proteins can rapidly traverse a complex energy surface.     

Effects of prenatal cocaine exposure on embryonic expression of sonic hedgehog

PURPOSE: To estimate the impact of visual impairment in older Australians on the use of community support services. METHODS: In the Blue Mountains Eye Study, 3654 people aged 49 or older were examined- 82.4% of eligible residents in an area west of Sydney, Australia. Presenting and best-corrected visual acuities were measured using a LogMAR chart. Subjects were categorized as having visual impairment if their better eye read 40 or fewer letters (20/40 or worse). Interview data included marital and other socioeconomic status measures, living status (alone or with spouse or other person), use of community support services, reliance on regular help from nonspouse family members or friends, and perceived ability to go out alone. RESULTS: After adjusting for age, gender, education, living status, walking disability, and health-related factors, for each one-line (five-letter) decrease in best-corrected visual acuity, there was a corresponding increase in reliance on community support services (odds ratio [OR], 1.17; 95% confidence interval, [CI] 1.07-1.28) or combined community and family support (OR 1.22; 95% CI, 1.12-1.32). Visually impaired persons were three times as likely to use regular support services provided by the municipality (OR 3.1; 95% CI, 1.8-5.1). A similar increased reliance on regular help from community, nonspouse family members, or friends was found. Visually impaired persons were also much more likely to state that they thought they were unable to go out alone (OR 6.2; 95% CI, 2.6-14.3). The findings were similar when presenting visual acuity was used to define visual impairment or after subjects with walking disabilities were excluded. Visual impairment seemed to have a greater effect on use of community support services in women than in men. CONCLUSIONS: After adjustment was made for confounding factors, visual impairment was found to affect significantly and negatively the independence of elderly people, particularly older women. Presenting visual acuity closely approximated best-corrected visual acuity in its impact on the use of community support services.     

Mosquito-Plasmodium interactions in response to immune activation of the vector

A molecular model was built for human lecithin:cholesterol acyltransferase (LCAT) based upon the structural homology between this enzyme and lipases (Peelman et al. 1998. Prot. Sci. 7: 585-597). We proposed that LCAT belongs to the alpha/beta hydrolase fold family, and that the central domain of LCAT consists of a mixed seven-stranded beta-pleated sheet with four alpha-helices and loops linking the beta-strands. The catalytic triad of LCAT was identified as Asp345 and His377, as well as Ser181. This model is used here for the interpretation of the structural defects linked to the point mutations identified in LCAT, which cause either familial LCAT deficiency (FLD) or fish-eye disease (FED). We show that these mutations occur in separate domains of the 3D structure of the enzyme. Most mutations causing familial LCAT deficiency are either clustered in the vicinity of the catalytic triad or affect conserved structural elements in LCAT. Most mutations causing fish-eye disease are localized on the outer hydrophilic surface of the amphipathic helical segments. These mutations affect only minimally the overall structure of the enzyme, but are likely to impair the interaction of the enzyme with its co-factor and/or substrate.     

Efflux pump-mediated quinolone resistance in Staphylococcus aureus strains wild type for gyrA, gyrB, grlA, and norA

Fluoroquinolone efflux was studied in 47 Staphylococcus aureus clinical strains with MICs of ciprofloxacin (CFX) of < or = 2 micrograms/ml. Forty-three strains were wild type for gyrA, gyrB, and grlA quinolone resistance-determining regions and for norA and its promoter region. Forty of these strains (MICs of CFX, 0.1 to 0.2 microgram/ml) did not show efflux of fluoroquinolones. Three strains (MICs of CFX, 1 to 2 micrograms/ml) showed efflux. These results suggest that efflux can appear in S. aureus clinical strains in the absence of mutations in norA and its promoter.