Cloning and characterization of Saccharomyces cerevisiae Nfs1p: An essential mitochondrial protein required for iron-sulfur cluster assembly and for cellular and mitochondrial iron homeostasis.

Format:

Book

Thesis/Dissertation

Author/Creator:

Li, Jie.

Contributor:

University of Pennsylvania.

Language:

English

Subjects (All):

Cytology.

Genetics.

Molecular biology.

0307.

0369.

0379.

Local Subjects:

0307.

0369.

0379.

Physical Description:

161 pages

Contained In:

Dissertation Abstracts International 61-06B.

System Details:

Mode of access: World Wide Web.

text file

Summary:

In the yeast Saccharomyces cerevisiae, the transcription factor Aft1P regulates the expression of numerous genes including the genes required for high-affinity iron transport at the cytoplasmic membrane. However, the mechanisms regulating iron homeostasis in subcellular organelles, especially in mitochondria, are largely unknown. In the work reported here, we describe the isolation of MA14, a mutant with defects in cellular and mitochondrial iron homeostasis. The expression of high-affinity iron uptake genes including FRE1, FRE2, FTR1, and FET3 are induced in an Aft1p dependent way in MA14 cells. Consequently MA14 cells have high rates of cellular iron uptake and show a desensitized response towards environmental iron. The excess iron is sequestered inside mitochondria matrix as Triton X-100 insoluble aggregates that are observable under EM. We further show that MA14 represents a missense allele (I191S) of the NFS1 gene. Nfs1p is the yeast homologue of the bacterial proteins, NifS and IscS, enzymes that release sulfur from cysteine for iron-sulfur cluster assembly. In this study, Nfs1p was localized to mitochondria and was shown to be essential for viability. Depletion of cellular Nfs1p led to rapid decline of Fe-S cluster enzyme activities and to disruption of iron homeostasis at both cellular and mitochondrial levels. Based on these results, we propose that Fe-S clusters or particular iron-sulfur proteins are involved in controlling cellular and mitochondrial iron homeostasis. The synthesis of Fe-S clusters and maturation of Fe-S cluster proteins in yeast probably requires the coordinated activities of as many as 10 gene products as well as the sequential or concerted actions of multiple chaperone proteins. The mutants of several of these genes have been isolated in our genetic screen. We present evidence in this study that components of a mitochondrial electron transport chain, which have not been isolated in our screen, might also be involved in Fe-S cluster assembly and iron homeostasis.

Notes:

Source: Dissertation Abstracts International, Volume: 61-06, Section: B, page: 2903.

Supervisor: Andrew Dancis.

Thesis (Ph.D.)--University of Pennsylvania, 2000.

Local Notes:

School code: 0175.

ISBN:

9780599821613

Access Restriction:

Restricted for use by site license.