dictyNews Electronic Edition Volume 33, number 14 November 27, 2009 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu or by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. Back issues of dictyNews, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. Follow dictyBase on twitter: http://twitter.com/dictybase ========= Abstracts ========= Autophagy dysfunction and Ubiquitin-positive protein aggregates in Dictyostelium Cells Lacking Vmp1. Javier Calvo-Garrido  and Ricardo Escalante Instituto de Investigaciones Biomédicas Alberto Sols. C.S.I.C./U.A.M., Calle Arturo Duperier 4, 28029 Madrid. Spain.   Autophagy, in press Ubiquitin-positive protein aggregates are a hallmark of many degenerative diseases. Their presence can be induced by dysfunction in protein degradation pathways such as proteasome and autophagy. We now report several lines of evidence suggesting a defect in autophagy in Dictyostelium cells lacking Vmp1 (Vacuole membrane protein 1), an endoplasmic reticulum (ER)-resident protein involved in pathological processes such as cancer and pancreatitis. vmp1- null cells are unable to survive starvation or undergo autophagic-cell-death under the appropriate inductive signals. Moreover, confocal studies using the autophagy marker Atg8 and previous transmission electron microscopy analysis showed defects in autophagosome formation.  Although Vmp1 is localized in the ER we found co-localization with Atg8 suggesting a contribution of both Vmp1 and ER in autophagosome biogenesis or maturation. Interestingly, vmp1- mutant cells showed accumulation of huge ubiquitin-positive protein aggregates containing the autophagy marker GFP-Atg8 and the putative Dictyostelium p62 homologue as described in many degenerative human diseases. The analysis of other Dictyostelium autophagic mutants  (atg1-, atg5-, atg6-, atg7- and atg8-) showed a correlation in the severity of their corresponding phenotypes and the presence of ubiquitin-positive protein aggregates suggesting that the deleterious effects associated with development of these aggregates might contribute to the complex phenotypes observed in autophagy deficient mutants. Our results suggest that Vmp1 is required for the clearance of these ubiquitinated protein aggregates through autophagy and highlight a potential role for Vmp1 in protein-aggregation diseases.  Submitted by Ricardo Escalante [rescalante2@gmail.com] -------------------------------------------------------------------------------- Transcription of the Dictyostelium discoideum mitochondrial genome occurs from a single initiation site Phuong Le, Paul Robert Fisher and Christian Barth Department of Microbiology, La Trobe University, Kingsbury Drive, Bundoora, Victoria 3086, Australia RNA, in press Transcription of the mitochondrial genome in Dictyostelium discoideum gives rise to eight major polycistronic RNA species that can be detected by Northern hybridization. In order to determine whether these transcripts could possibly derive from processing of even larger transcripts, Reverse Transcriptase Polymerase Chain Reactions (RT-PCR) were performed in an attempt to amplify the intervening regions between the eight major transcripts. All but one intervening regions were successfully reverse transcribed and amplified, indicating that even larger transcripts existed and that the eight major transcripts detected previously may be the products of transcript processing. Southern hybridization analyses of DNA fragments representing the sequences between the eight major transcripts with in vitro capped mitochondrial RNA identified the 5' end of only one of the eight major transcripts as a genuine transcription start site. The ability to initiate transcription from DNA sequences upstream of the identified transcription initiation site was demonstrated in bacterial cells expressing the Dictyostelium mitochondrial RNA polymerase. We conclude that transcription of the Dictyostelium mitochondrial genome is initiated at a single site, generating a large polycistronic transcript that is very efficiently, probably co-transcriptionally, processed into mature RNA species. This is the first report on a protist mitochondrial DNA that is, although much larger in size than its metazoan counterparts, transcribed from a single transcription initiation site. Submitted by Christian Barth [c.barth@latrobe.edu.au] ============================================================== [End dictyNews, volume 33, number 14]