RNA polymerase III interferes with Ty3 integration.

Ty3, a gypsylike retrotransposon of budding yeast, integrates at the transcription initiation site of genes transcribed by RNA polymerase III (pol III). It was previously shown that integration in vitro requires intact promoter elements and the pol III transcription factors TFIIIB and TFIIIC. In order to test the effect of pol III on integration, increasing amounts of a pol III-containing fraction were added to Ty3 in vitro integration reactions. The pol III-containing fraction was inhibitory to integration. These results are consistent with a model where the Ty3 integration complex and pol III recognize similar features of the stable transcription complex and compete with each other for access to the transcription initiation site.

Requirement of RNA polymerase III transcription factors for in vitro position-specific integration of a retroviruslike element.

The yeast retroviruslike element Ty3 inserts at the transcription initiation sites of genes transcribed by RNA polymerase III (Pol III). An in vitro integration assay was developed with the use of Ty3 viruslike particles and a modified SUP2 tyrosine transfer RNA (tRNA(Tyr)) gene target. Integration was position-specific and required Ty3 integrase, Pol III transcription factor (TF) IIIB-, TFIIIC-, and Pol III-containing fractions showed that TFIIIB and TFIIIC, together, were sufficient for position-specific Ty3 integration, but not for transcription. This report demonstrates that in vitro integration of a retroelement can be targeted by cellular proteins.

Selective decontamination with nystatin for control of a Candida outbreak in a neonatal intensive care unit.

Selective decontamination of the digestive tract (SDD) with oral nystatin was evaluated as a measure to control an outbreak of Candida infection in a neonatal intensive care unit (NICU). Seventy-six out of 106 neonates who carried Candida spp. received the main study manoeuvre (the application of oral nystatin in the throat and stomach) during the 12-month open trial. One third of the neonates weighed < 1500 g whilst about half were being ventilated. The mean stay was 33.2 d (SD +/- 46.9). Two cases with candidaemia within a fortnight were associated with a yeast carriage rate in the NICU of about 50%; more than 80% of the isolates were Candida parapsilosis. During the implementation period there were four new neonates with fungaemia caused by C. parapsilosis. Once the carriage rate dropped below 5% (P < 0.001), no new cases of systemic infection with the outbreak strain were recognized in the following 8 months. It took 3.5 months to control the outbreak. The observation that all other clinical diagnostic samples were free from Candida suggests that translocation from throat or gut into the systemic circulation occurred. SDD with oral nystatin was effective in reducing the yeast carriage index (mean index 1.93, before SDD; 0.45, after SDD; P < 0.001). A significant reduction of carriage, both in rates and indices, is thought to have contributed to the control of this candida outbreak.

Sequence of pedal peptide: a novel neuropeptide from the central nervous system of Aplysia.

We report the identification of a novel neuropeptide from Aplysia nervous tissue. The peptide was termed Pedal peptide (Pep) because it was predominantly synthesized in the pedal ganglia. Pep was purified and sequenced from pooled extracts of pedal ganglia. The following sequence was proposed: Pro-Leu-Asp-Ser-Val-Tyr-Gly-Thr-His-Gly-Met-Ser-Gly-Phe-Ala. Enzymatic hydrolysis procedures indicated that Pep had a free carboxyl terminal. A peptide with the proposed sequence was synthesized and compared with the native peptide. Chromatographic properties of the 2 peptides under 3 different conditioned were compared and found to be identical. Electrophysiological responses to the 2 peptides were compared on an identified neuron in the abdominal ganglia and found to be qualitatively and quantitatively very similar. Both peptides produced net inward currents that were associated with a decrease in membrane conductance. The results from these 2 procedures confirmed that the proposed Pep sequence was correct. Quantitative measurements of the incorporation of 35S-methionine into Pep suggest that cell bodies that synthesize Pep were present predominantly in the pedal ganglia but should also be found in other central ganglia as well. Pep-like immunoreactive neurons are found predominantly in the pedal ganglia and less frequently in the other ganglia (Pearson and Lloyd, 1989). Quantitatively, Pep constitutes one of the predominant peptides in the nervous system of Aplysia. Pep does not appear to be a member of any other previously identified invertebrate or vertebrate peptide family.