Specificity of DNA-binding by the FAX-1 and NHR-67 nuclear receptors of Caenorhabditis elegans is partially mediated via a subclass-specific P-box residue

<p>Abstract</p> <p>Background</p> <p>The nuclear receptors of the NR2E class play important roles in pattern formation and nervous system development. Based on a phylogenetic analysis of DNA-binding domains, we define two conserved groups of orthologous NR2E genes: the NR2E1 subclass, which includes <it>C. elegans nhr-67, Drosophila tailless </it>and <it>dissatisfaction</it>, and vertebrate Tlx (NR2E2, NR2E4, NR2E1), and the NR2E3 subclass, which includes <it>C. elegans fax-1 </it>and vertebrate PNR (NR2E5, NR2E3). PNR and Tll nuclear receptors have been shown to bind the hexamer half-site AAGTCA, instead of the hexamer AGGTCA recognized by most other nuclear receptors, suggesting unique DNA-binding properties for NR2E class members.</p> <p>Results</p> <p>We show that NR2E3 subclass member FAX-1, unlike NHR-67 and other NR2E1 subclass members, binds to hexamer half-sites with relaxed specificity: it will bind hexamers with the sequence ANGTCA, although it prefers a purine to a pyrimidine at the second position. We use site-directed mutagenesis to demonstrate that the difference between FAX-1 and NHR-67 binding preference is partially mediated by a conserved subclass-specific asparagine or aspartate residue at position 19 of the DNA-binding domain. This amino acid position is part of the "P box" that plays a critical role in defining binding site specificity and has been shown to make hydrogen-bond contacts to the second position of the hexamer in co-crystal structures for other nuclear receptors. The relaxed specificity allows FAX-1 to bind a much larger repertoire of half-sites than NHR-67. While NR2E1 class proteins bind both monomeric and dimeric sites, the NR2E3 class proteins bind only dimeric sites. The presence of a single strong site adjacent to a very weak site allows dimeric FAX-1 binding, further increasing the number of dimeric binding sites to which FAX-1 may bind <it>in vivo</it>.</p> <p>Conclusion</p> <p>These findings identify subclass-specific DNA-binding specificities and dimerization properties for the NR2E1 and NR2E3 subclasses. For the NR2E1 protein NHR-67, Asp-19 permits binding to AAGTCA half-sites, while Asn-19 permits binding to AGGTCA half-sites. The apparent conservation of DNA-binding properties between vertebrate and nematode NR2E receptors allows for the possibility of evolutionarily-conserved regulatory patterns.</p

Ten Years of Surveillance for Invasive Streptococcus pneumoniae during the Era of Antiretroviral Scale-Up and Cotrimoxazole Prophylaxis in Malawi

OBJECTIVE: To document trends in invasive pneumococcal disease (IPD) in a central hospital in Malawi during the period of national scale-up of antiretroviral therapy (ART) and cotrimoxazole prophylaxis. METHODS: Between 1 January 2000 and 31 December 2009 almost 100,000 blood cultures and 40,000 cerebrospinal fluid (CSF) cultures were obtained from adults and children admitted to the Queen Elizabeth Central Hospital, Blantyre, Malawi with suspected severe bacterial infection. RESULTS: 4,445 pneumococcal isolates were obtained over the 10 year period. 1,837 were from children: 885 (19.9%) from blood and 952 (21.4%) from CSF. 2,608 were from adults: 1,813 (40.8%) from blood and 795 (17.9%) from CSF. At the start of the surveillance period cotrimoxazole resistance was 73.8% and at the end was 92.6%. Multidrug resistance (MDR) was present in almost one third of isolates and was constant over time. Free ART was introduced in Malawi in 2004. From 2005 onwards there was a decline in invasive pneumococcal infections with a negative correlation between ART scale-up and the decline in IPD (Pearson's correlation r = -0.91; p<0.001). CONCLUSION: During 2004-2009, national ART scale-up in Malawi was associated with a downward trend in IPD at QECH. The introduction of cotrimoxazole prophylaxis in HIV-infected groups has not coincided with a further increase in pneumococcal cotrimoxazole or multidrug resistance. These data highlight the importance of surveillance for high disease burden infections such as IPD in the region, which will be vital for monitoring pneumococcal conjugate vaccine introduction into national immunisation programmes

A new species of Ctenophorus (Lacertilia: Agamidae) from Lake Disappointment Western Australia

Copyright © 2007 Allen PressCtenophorus is the largest genus of Australian agamid lizards, with an extensive radiation in the arid zone. Here we describe a distinctive new dragon species—Ctenophorus nguyarna—from the isolated Lake Disappointment in Western Australia. The new species is characterised by heterogeneous dorsal scales tending to form vertical rows on the flanks, a reticulated orange and black background color, and black bars on the dorsum and black vertical bars on the tail. To provide a molecular context as to the distinctiveness and placement of the new species we analysed five sequences of Ctenophorus sp. nov., two new sequences of C. salinarum and 11 previously published sequences of Ctenophorus species, representing 1573 bases of the mitochondrial genome. Our phylogeny strongly supports at least two independent origins of salt lake specialization in both the western and eastern arid zone. Based on molecular data the sister taxon is C. salinarum, which is also associated with salt lakes in Western Australia. The other specialist is the Lake Eyre Dragon (C. maculosus) from South Australia that lives on and under the salt crust itself, and has a number of unique derived characters for Ctenophorus. There are likely to be other new species of agamid lizards in Australia's vast and little-explored arid zone

Times to drink: cross-cultural variations in drinking in the rhythm of the week

OBJECTIVES: The time of drinking in terms of daytime versus evening and weekday versus weekend is charted for regular drinkers in 14 countries in Europe, Asia, Latin America, Africa and Oceania. METHODS: national or regional adult population surveys from the GENACIS project. Results: The weekly rhythm of drinking varies greatly between societies. Drinking was generally more likely after 5 pm and on weekends. To this extent, alcohol consumption is now regulated by a universal clock. The relation of time of day and of the week of drinking to problems from drinking varied between societies. Drinking at specific times was more likely to predict problems among men than women, though for men the particular time varied, while weekday evenings were the most problematic time for women. The relation of drinking at a particular time to problems in part reflected that heavy drinkers were more likely to be drinking at that time. CONCLUSIONS: There are commonalities across cultures in drinking by time of day and day of the week, but the implications of the timing for alcohol-related problems are fairly culture-specific