Dissertation/Thesis Abstract

Intersection of RNA processing and fatty acid synthesis and attachment in yeast mitochondria
by Schonauer, Melissa Suzanne, Ph.D., The University of Arizona, 2008, 158; 3330862
Abstract (Summary)

Intersections of distinct biological pathways in cells allow for nodes of metabolic regulation. This work describes the discovery of the intersection of two pathways in yeast mitochondria: RNA processing and fatty acid synthesis and attachment. Analysis of the components of the pathways is presented here along with a model illustrating the connection as a potential mode of regulation of mitochondrial gene expression.

A genome-wide screen of respiratory-deficient Saccharomyces cerevisiae deletion strains for defects in mitochondrial RNA processing revealed that two novel genes affect processing of mitochondrial tRNAs by RNase P. One gene encodes Htd2, an enzyme in the type II mitochondrial fatty acid synthesis pathway (FAS II). The other gene is described here as encoding Lip3, an enzyme involved in the synthesis and attachment of the co-factor lipoic acid, which is synthesized from a product of the FAS II pathway.

RPM1 is the mitochondrial-encoded RNA subunit of mitochondrial RNase P. The multigenic transcription unit containing RPM1 also contains tRNA pro. Maturation of RPM1 necessitates processing of the tRNA by RNase P. Thus, RNase P is required for maturation of its own RNA component, constituting a positive feedback cycle. The present work demonstrates that a product of the FAS II pathway is necessary for the assembly or activity of RNase P, as deletion of any gene encoding an FAS II enzyme results in inefficient processing of tRNApro from the transcript.

Analysis of the enzymes involved in the synthesis and attachment of lipoic acid to target proteins is also described here. Disruption of any of these enzymes affects protein lipoylation and tRNA processing. Gcv3, a target of lipoylation, was found to be required for lipoylation as well as for efficient tRNA processing.

A second feedback cycle controlling pyruvate dehydrogenase activity and fatty acid synthesis may be functional under certain conditions. Pyruvate dehydrogenase, which provides acetyl-CoA for the FAS II pathway, requires lipoic acid for its activity. It is hypothesized that the two feedback cycles and the role of Gcv3 may provide switch-like regulation of mitochondrial gene expression in response to the nutritional state of the cell.

Indexing (document details)
Advisor: Dieckmann, Carol L.
Commitee: Dieckmann, Carol L., Tax, Frans, Weinert, Ted
School: The University of Arizona
Department: Molecular & Cellular Biology
School Location: United States -- Arizona
Source: DAI-B 69/10, Dissertation Abstracts International
Subjects: Molecular biology
Keywords: Fatty acid synthesis, Mitochondria, RNA processing
Publication Number: 3330862
ISBN: 978-0-549-87531-4
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