Decapping is a critical step in mRNA decay. In the 59-to-39 mRNA decay pathway conserved in all eukaryotes, decay is initiated by poly(A) shortening, and oligoadenylated mRNAs (but not polyadenylated mRNAs) are selectively decapped allowing their subsequent degradation by 59 to 39 exonucleolysis. The highly conserved heptameric Lsm1p-7p complex (made up of the seven Sm-like proteins, Lsm1p-Lsm7p) and its interacting partner Pat1p activate decapping by an unknown mechanism and localize with other decapping factors to the P-bodies in the cytoplasm. The Lsm1p-7p-Pat1p complex also protects the 39-ends of mRNAs in vivo from trimming, presumably by binding to the 39-ends. In order to determine the intrinsic RNA-binding properties of this complex, we have purified it from yeast and carried out in vitro analyses. Our studies revealed that it directly binds RNA at/near the 39-end. Importantly, it possesses the intrinsic ability to distinguish between oligoadenylated and polyadenylated RNAs such that the former are bound with much higher affinity than the latter. These results indicate that the intrinsic RNAbinding characteristics of this complex form a critical determinant of its in vivo interactions and functions.

Abstract. The phlebotomine sand fly Lutzomyia longipalpis is the insect vector of visceral leishmaniasis, a protozoan disease of increasing incidence and distribution in Central and South America. Electrophoretic allele frequencies of 15 enzyme loci were compared among the L. longipalpis populations selected across its distribution range in Brazil. The mean heterozygosity of two colonized geographic strains (one each from Colombia and Brazil) were 6% and 13% respectively, with 1.6-1.9 alleles detected per locus. In contrast, among the seven widely separated field populations, the mean heterozygosity ranged from 11% to 16% with 2.1-2.9 alleles per locus. No locus was recovered that was diagnostic for any of the field populations. Allelic frequency differences among five field strains from the Amazon basin and eastern coastal Brazil were very low, with Nei's genetic distances of less than 0.01 separating them. The two inland and southerly samples from Minas Gerais (Lapinha) and Bahia (Jacobina) states were more distinctive with genetic distances of 0.024-0.038 and 0.038-0.059, respectively, when compared with the five other samples. These differences were the consequence of several high frequency alleles (glycerol-3-phosphate dehydrogenase [Gpd 1.69 ] and phosphoglucomutase [Pgm 1.69 ]) relatively uncommon in other strains. The low genetic distances, absence of diagnostic loci, and the distribution of genes in geographic space indicate L. longipalpis of Brazil to be a single, but genetically heterogeneous, polymorphic species.American visceral leishmaniasis (kala-azar) is a fatal disease in the New World tropics. Approximately 1.6 million people are at risk of infection with this disease and on average, 16,000 cases are reported annually. 1,2 More than 90% of human cases occur in Brazil. 3,4 Visceral leishmaniasis in humans is caused by the kinetoplastid protozoan Leishmania donovani chagasi Cunha and Chagas. 5,6 However, in Central America, infections also frequently result in cutaneous disease. [7][8][9] The most important vector of Leishmania d. chagasi is the phlebotomine sand fly Lutzomyia longipalpis (Lutz and Neiva). 10-13 It was first described from specimens collected in São Paulo Bosque de Saúde (no longer in existence), 100 km north northwest of Belo Horizonte at the Caves of Maquiné (Cordisburgo) and at a ranch near the river port of Benjamin Constant (Além Paraíba, 140 km northeast of Rio de Janeiro) Fazenda Ouro Fino. 14,15 It occurs from southern Mexico to northern Argentina in discontinuous distributions. 16 In Brazil, L. longipalpis has been recorded in habitats ranging from heavily populated urban centers to rural, periurban areas in a wide variety of ecotopes including mountain ranges to the east and the Amazon river basin covering most of the north and central Brazil. Therefore, the sand flies survive in a variety of habitats and sometimes in zones where formidable barriers prevent their migration. Since they have a limited flight range, rarely migrating more than 100 meters, the widely separ...

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BackgroundCutaneous leishmaniasis is a neglected, vector-borne parasitic disease and is responsible for persistent, often disfiguring lesions and other associated complications. Leishmania, causing zoonotic cutaneous leishmaniasis (ZCL) in the Old World are mainly transmitted by the predominant sand fly vector, Phlebotomus papatasi. To date, there is no efficient control measure or vaccine available for this widespread insect-borne infectious disease.Methodology/Principal FindingsA survey was carried out to study the abundance of different natural gut flora in P. papatasi, with the long-term goal of generating a paratransgenic sand fly that can potentially block the development of Leishmania in the sand fly gut, thereby preventing transmission of leishmania in endemic disease foci. Sand flies, in particular, P. papatasi were captured from different habitats of various parts of the world. Gut microbes were cultured and identified using 16S ribosomal DNA analysis and a phylogenetic tree was constructed. We found variation in the species and abundance of gut flora in flies collected from different habitats. However, a few Gram-positive, nonpathogenic bacteria including Bacillus flexus and B. pumilus were common in most of the sites examined.Conclusion/SignificanceOur results indicate that there is a wide range of variation of aerobic gut flora inhabiting sand fly guts, which possibly reflect the ecological condition of the habitat where the fly breeds. Also, some species of bacteria (B. pumilus, and B. flexus) were found from most of the habitats. Important from an applied perspective of dissemination, our results support a link between oviposition induction and adult gut flora.

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