The fragile X mental retardation protein interacts with a distinct mRNA nuclear export factor NXF2

Loss of fragile X mental retardation protein, FMRP, causes the fragile X syndrome. Highly expressed in the brain and testis, FMRP has been implicated in the transport and translation of specific mRNAs. Here we show that FMRP and the mRNA nuclear export factor NXF2 co-express in the mouse male germ cells and hippocampal neurons and that FMRP associates with NXF2 but not with its close relative NXF1. We thus hypothesize that FMRP and NXF2 may act in concert to promote the nucleocytoplasmic transport of specific mRNAs in male germ cells and neurons.     

Synthesis and structure-activity relationships of soluble 8-substituted 4-(2-chlorophenyl)-9-hydroxypyrrolo[3,4-c]carbazole-1,3(2H,6H)-diones as inhibitors of the Wee1 and Chk1 checkpoint kinases

Pyrrolo[3,4-c]carbazoles bearing solubilising basic side chains at the 8-position retain potent Wee1 and Chk1 inhibitory properties in isolated enzyme assays, and evidence of G2/M checkpoint abrogation in several cellular assays. Co-crystal structure studies confirm that the primary binding to the Wee1 enzyme is as described previously, with the C-8 side chains residing in an area of bulk tolerance.     

Targeted isolation of simple sequence repeat markers through the use of bacterial artificial chromosomes

 Simple sequence repeats (SSRs) are versatile DNA markers that are readily assayed and highly informative. Unfortunately, non-targeted approaches to SSR development often leave large genomic regions without SSR markers. In some cases these same genomic regions are already populated by other types of DNA markers, especially restriction fragment length polymorphisms (RFLPs), random amplified polymorphic DNAs (RAPDs), and amplified fragment length polymorphisms (AFLPs). To identify SSR markers in such regions, bacterial artificial chromosome (BAC) clones can be used as intermediaries. First, one or more BAC clones in a region of interest are identified through the use of an existing DNA marker. BAC clones uncovered in this initial step are then used to create a small insert DNA library that can be screened for the presence of SSR-containing clones. Because BAC inserts are often 100-kb pairs or more in size, most contain one or more SSRs. This strategy was applied to two regions of the soybean genome near genes that condition resistance to the soybean cyst nematode on molecular linkage groups G and A2. This targeted approach to identifying new DNA markers can readily be extended to other types of DNA markers, including single nucleotide polymorphisms. Received: 13 August 1998 / Accepted: 13 October 1998     

Laboratory bioassays of entomopathogenic fungi for control of Delia radicum (L.) larvae

Laboratory soil bioassays were performed at economic field rates for in-furrow (3.85 x 10(6)spores/g dry soil) and broadcast (3.85 x 10(5)spores/g dry soil) applications with three isolates of Metarhizium anisopliae (F52, ATCC62176, and ARSEF5520) and one isolate of Beauveria bassiana (GHA). All isolates tested were infective to second instar Delia radicum (L.). The conditionally registered M. anisopliae isolate (F52) performed best killing an average of 85 and 72% of D. radicum larvae at the high and low concentration, respectively. The mean LC50 and LC95 of F52 against second instar D. radicum was 2.7 x 10(6) and 1.8 x 10(8)spores/g dry soil, respectively. The use of F52 in an integrated management program is discussed.     

Heavy metals in Lake George, Uganda, with relation to metal concentrations in tissues of common fish species

The northern end of Lake George, Uganda, and its associated wetlands receive localized metal pollution from a former copper mine and tailings left after metal extraction. The aim of this study was to determine (i) whether the heavy metals are a threat to the biology of the major commercial fish species and (ii) whether consumption of the fish threatens human health. Concentrations of copper, zinc, cobalt and nickel in detrital sediments, plankton, and five fish species from sites in Lake George, the Kazinga Channel and Lake Edward (which are inter-connected) were determined using atomic absorption spectroscopy. The detrital sediments of Hamukungu Bay, Lake George, had average concentrations (g/g dry weight) of 96.3 zinc, 270.4 copper, 57.4 cobalt and 42.8 nickel. There were no significant differences between the Hamukungu Bay and the North Lake George site of Bushatu: both receive inflows from the mining activities. Concentrations of copper and zinc were significantly higher than background values from unpolluted freshwater ecosystems. Plankton samples showed a metal concentration gradient consistent with a gradient from the source of pollution in northern Lake George, along the Kazinga Channel to Lake Edward. The liver tissues of fish had markedly higher concentrations of copper and zinc than flesh. Concentrations of cobalt and nickel were relatively low. The highest mean concentrations of metals in liver tissue occurred in Oreochromis leucostictus (189.0 g/g Cu) and Bagrus docmac (187.5 g/g Zn) whilst the lowest occurred in Oreochromis niloticus (15.3 g/g and 78.2 g/g dry weight copper and zinc, respectively). However, O. niloticus contained the highest concentrations of cobalt (11.2 g/g) and nickel (3.8 g/g). Liver Somatic Indices (LSI) of the fish species from the different sites indicated a reduction of LSI in those fish from the most contaminated zones of northern Lake George compared with all other sites. This suggests there could be anatomical and physiological abnormalities linked to the heavy metal pollution. The flesh had only low concentrations of metals; well within international guidelines for consumption. A person would have to consume 9 kg of fresh flesh of Clarias sp. and 65 kg of O. leucostictus daily to exceed the WHO recommended intake for copper, and even more for other metals. This implies that currently metal pollution in Lake George presents an ecological rather than a human health concern.     

The interaction of DNA-targeted 9-aminoacridine-4-carboxamide platinum complexes with DNA in intact human cells

As part of an ongoing drug development programme, this paper describes the sequence specificity and time course of DNA adduct formation for a series of novel DNA-targeted analogues of cis-diaminedichloroplatinum(II) (cisplatin) (9-aminoacridine-4-carboxamide Pt complexes) in intact HeLa cells. The sequence specificity of DNA damage caused by cisplatin and analogues in human (HeLa) cells was studied using Taq DNA polymerase and a linear amplification/polymerase stop assay. Primer extension is inhibited by a Pt-DNA adduct, and hence the sites of these lesions can be analysed on DNA sequencing gels. The repetitive alphoid DNA sequence was used as the target DNA in human cells. The 9-aminoacridine-4-carboxamide Pt complexes exhibited a markedly different sequence specificity relative to cisplatin and other analogues. The sequence specificity of the 9-aminoacridine-4-carboxamide Pt complexes is shifted away from a preference for runs of guanines. The 9-aminoacridine-4-carboxamide Pt complexes have an enhanced preference for GA dinucleotides. This is the first occasion that an altered DNA sequence specificity has been demonstrated for a cisplatin analogue in human cells. A time course of DNA damage revealed that the DNA-targeted Pt complexes, consisting of four 9-aminoacridine-4-carboxamide Pt complexes and one acridine-4-carboxamide Pt complex, damaged DNA more rapidly compared to cisplatin and non-targeted analogues. A comparison of the time taken to reach half the maximum relative intensity indicated that the DNA-targeted Pt complexes reacted approximately 4-fold faster than cisplatin and the non-targeted analogues.