Genomes and Genes
Nutritional Copper Signaling and Homeostasis
Principal Investigator: Sabeeha Merchant
Abstract: DESCRIPTION (provided by applicant): Cu is an essential nutrient for nearly all forms of life because it serves as an enzyme prosthetic group for catalyzing redox reactions or reactions involving O2 chemistry. These reactions are central to aerobic life. Our long term goal is to understand the metabolism of copper, especially when it is a limiting nutrient or in a situation of metabolic defect. Two decades ago, we discovered the paradigm of Cu sparing in the model organism, Chlamydomonas, where a Cu-independent protein can, in a situation of Cu-deficiency, replace an otherwise abundant Cu protein. The wide-spread occurrence of this mechanism in many microbial systems for various trace mineral nutrients (Fe, Zn, Mo, to list a few) is now well-established. Metal sparing mechanisms are likely to be important for the success of certain infectious bacteria and fungi in evading host defense systems, where metal sequestration is used as a defensive strategy. A new paradigm, discovered in the previous project period, is Cu "salvage", in which Cu is removed from a non-essential protein so that it can be recycled and used for the synthesis of an essential cuproprotein. In Chlamydomonas, replacement and salvage mechanisms are turned on in copper-deficient cells by a copper-sensing transcription factor, CRR1. Its target genes are associated with copper response elements, which serve as binding sites for the DNA binding domain of CRR1. We have identified all the CRR1 target genes in the Chlamydomonas genome by next gen transcriptome profiling (RNA-Seq). In Specific Aim 1, we will undertake biochemical and reverse genetic analysis of select target genes, IRT2 (encoding a ZIP family FeII transporter), AOF1 (encoding a flavin amine oxidase), 142634 (encoding a down-regulated plastid-targeted metallochaperone) to further elaborate the copper sparing pathway, and of RSEP1 (encoding a thylakoid lumen protease) and CTR3 (encoding a soluble copper binding protein) to assess their function in the salvage pathway. In zinc-deficient Chlamydomonas cells, copper is hyper-accumulated in bio-inaccessible compartments, resulting in functional copper-deficiency. This phenotype has been observed recently in mammalian cells with disruptions in Cu homeostasis factors. Hyper- accumulation of Cu in Chlamydomonas requires CRR1. In Aim 2, we will undertake biochemical characterization of these copper-loaded compartments and we will use high throughput screening methods for a classical genetic approach for the discovery of factors involved in loading and unloading Cu into these compartments. CRR1 is also required in Chlamydomonas for zinc homeostasis. Besides ZIP family transporters, two novel proteins, 123019 and 117548, with COG0523 domains (conserved in all kingdoms of life) are highly up-regulated in zinc-deficiency. In Aim 3, we will distinguish the mechanism of regulation of the corresponding genes, identify zinc response elements, and use gain-of-function mutants (by over-expression) to deduce whether they are zinc chaperones.
Funding Period: 1989-06-01 - 2016-04-30
more information: NIH RePORT
- The Chlamydomonas genome reveals the evolution of key animal and plant functionsSabeeha S Merchant
Department of Chemistry and Biochemistry, University of California at Los Angeles, Los Angeles, CA 90095, USA
Science 318:245-50. 2007....
- Systems biology approach in Chlamydomonas reveals connections between copper nutrition and multiple metabolic stepsMadeli Castruita
Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA
Plant Cell 23:1273-92. 2011..Forty percent of the targets are previously uncharacterized proteins, indicating considerable potential for new discovery in the biology of copper...
- A revised mineral nutrient supplement increases biomass and growth rate in Chlamydomonas reinhardtiiJanette Kropat
Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095 1569, USA
Plant J 66:770-80. 2011..Fe and Zn deficiency also induced TAG accumulation, as suggested by Nile Red staining. This approach can be used to efficiently optimize culture conditions for other algal species to improve growth and to assay cell physiology...
- Zinc binding drives sheet formation by the SAM domain of diacylglycerol kinase δMary Jane Knight
Department of Chemistry and Biochemistry, Institute of Genomics and Proteomics, University of California, Los Angeles, CA 90095 1570, USA
Biochemistry 49:9667-76. 2010..These results suggest that zinc may play an important role in the assembly and physiology of the DGKδ isozyme...
- Relationship between nucleosome positioning and DNA methylationRamakrishna K Chodavarapu
Department of Molecular, Cell, and Developmental Biology, University of California Los Angeles, Los Angeles, California 90095, USA
Nature 466:388-92. 2010..DNA methylation is also enriched on exons, consistent with the targeting of DNA methylation to nucleosomes, and suggesting a role for DNA methylation in exon definition...
- A subset of the diverse COG0523 family of putative metal chaperones is linked to zinc homeostasis in all kingdoms of lifeCrysten E Haas
Department of Microbiology and Cell Science, University of Florida, Gainesville, FL, USA
BMC Genomics 10:470. 2009..Even though the first COG0523-encoding gene, cobW, was identified almost 20 years ago, little is known concerning the function of other members belonging to this ubiquitous family...
- Two Chlamydomonas CTR copper transporters with a novel cys-met motif are localized to the plasma membrane and function in copper assimilationM Dudley Page
Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095 1569, USA
Plant Cell 21:928-43. 2009..Thus, Chlamydomonas CTR genes encode a distinct subset of the classical CTR family of Cu(I) transporters and represent new targets of CRR1-dependent signaling...
- A ferroxidase encoded by FOX1 contributes to iron assimilation under conditions of poor iron nutrition in ChlamydomonasJen Chih Chen
Department of Chemistry and Biochemistry, Box 951569, University of California Los Angeles, Los Angeles, CA 90095 1569, USA
Eukaryot Cell 7:541-5. 2008..Alternative pathways for iron assimilation, such as those involving ZIP family transporters IRT1 and IRT2, may be operational...
- Copper response regulator1-dependent and -independent responses of the Chlamydomonas reinhardtii transcriptome to dark anoxiaAnja Hemschemeier
Ruhr Universitat Bochum, Fakultät für Biologie und Biotechnologie, Arbeitsgruppe Photobiotechnologie, 44801 Bochum, Germany
Plant Cell 25:3186-211. 2013..Based on transcript patterns and previous results, we conclude that nitric oxide-dependent signaling cascades operate in anoxic C. reinhardtii cells...
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