Bt toxin resistance from loss of a putative carbohydrate-modifying enzyme.

The development of resistance is the main threat to the long-term use of toxins from Bacillus thuringiensis (Bt) in transgenic plants. Here we report the cloning of a Bt toxin resistance gene, Caenorhabditis elegans bre-5, which encodes a putative beta-1,3-galactosyltransferase. Lack of bre-5 in the intestine led to resistance to the Bt toxin Cry5B. Wild-type but not bre-5 mutant animals were found to uptake toxin into their gut cells, consistent with bre-5 mutants lacking toxin-binding sites on their apical gut. bre-5 mutants displayed resistance to Cry14A, a Bt toxin lethal to both nematodes and insects; this indicates that resistance by loss of carbohydrate modification is relevant to multiple Bt toxins.

Overexpression of translation elongation factor 1A affects the organization and function of the actin cytoskeleton in yeast.

The translation elongation factor 1 complex (eEF1) plays a central role in protein synthesis, delivering aminoacyl-tRNAs to the elongating ribosome. The eEF1A subunit, a classic G-protein, also performs roles aside from protein synthesis. The overexpression of either eEF1A or eEF1B alpha, the catalytic subunit of the guanine nucleotide exchange factor, in Saccharomyces cerevisiae results in effects on cell growth. Here we demonstrate that overexpression of either factor does not affect the levels of the other subunit or the rate or accuracy of protein synthesis. Instead, the major effects in vivo appear to be at the level of cell morphology and budding. eEF1A overexpression results in dosage-dependent reduced budding and altered actin distribution and cellular morphology. In addition, the effects of excess eEF1A in actin mutant strains show synthetic growth defects, establishing a genetic connection between the two proteins. As the ability of eEF1A to bind and bundle actin is conserved in yeast, these results link the established ability of eEF1A to bind and bundle actin in vitro with nontranslational roles for the protein in vivo.

Novel mutations and a mutational hotspot in the MODY3 gene.

Maturity-onset diabetes of the young 3 (MODY3) is a type of NIDDM caused by mutations in the transcription factor hepatocyte nuclear factor-1alpha (HNF-1alpha) located on chromosome 12q. We have identified four novel HNF-1alpha missense mutations in MODY3 families. In four additional and unrelated families, we observed an identical insertion mutation that had occurred in a polycytidine tract in exon 4. Among those families, one exhibited a de novo mutation at this location. We propose that instability of this sequence represents a general mutational mechanism in MODY3. We observed no HNF-1alpha mutations among 86 unrelated late-onset diabetic patients with relative insulin deficiency. Hence mutations in this gene appear to be most strongly associated with early-onset diabetes.