Iron is an essential nutrient that functions as a key co-factor for many cellular proteins involved in aerobic respiration, nucleotide metabolism, gene expression, and DNA repair. Given its central role in sustaining life, it is not surprising that cells have established a variety of elaborate regulatory mechanisms to control iron availability and usage. While characterizing components of the ubiquitination machinery that are deregulated in tumorigenesis, we identified a ubiquitin ligase subunit called FBXL5. In preliminary work, we demonstrated the FBXL5 is a novel regulator of iron metabolism that proteolytically controls the expression of important effectors of iron metabolism and cytoplasmic iron-sulfur cluster assembly. The major goal of this proposal is to examine the biological mechanisms by which FBXL5 regulates and is regulated by iron-related pathways.
In specific aim 1, we will examine the molecular basis of the iron-regulated interaction of FBXL5 with IRP2, a key regulator of iron homeostasis. The experiments in specific aim 2 will revolve around the regulation of FBXL5 itself and elucidating the novel proteolytic pathway responsible for its proteasome-dependent degradation under conditions of low iron availability.
Specific aim 3 will focus on the establishing the functional relevance of the interaction between FBXL5 and MMS19 and CIAO1, two putative components of the cytosolic iron assembly (CIA) pathway which is required for the assembly of Fe/S clusters in extramitochondrial proteins. Investigation of these three aims will provide a comprehensive view of how FBXL5 is able to influence multiple iron-associated processes. Ultimately, we hope that this work will offer insight into how the deregulation of FBXL5 and its downstream pathways may contribute to tumorigenesis while simultaneously highlighting potential new therapeutic strategies.

Public Health Relevance

The attachment of the ubiquitin to proteins is an important signal for cellular communication and is believed to be disrupted in multiple diseases including cancer, neurodegenerative diseases such as Huntington's disease, and diabetes. This proposal is focused on understanding how cells use this tagging system to regulate iron levels and usage.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Cellular Signaling and Regulatory Systems Study Section (CSRS)
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Maas, Stefan
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University of California Los Angeles
Schools of Medicine
Los Angeles
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Freire, Eden R; Malvezzi, Amaranta M; Vashisht, Ajay A et al. (2014) Trypanosoma brucei translation initiation factor homolog EIF4E6 forms a tripartite cytosolic complex with EIF4G5 and a capping enzyme homolog. Eukaryot Cell 13:896-908
Saada, Edwin A; Kabututu, Z Pius; Lopez, Miguel et al. (2014) Insect stage-specific receptor adenylate cyclases are localized to distinct subdomains of the Trypanosoma brucei Flagellar membrane. Eukaryot Cell 13:1064-76
Freire, Eden R; Vashisht, Ajay A; Malvezzi, Amaranta M et al. (2014) eIF4F-like complexes formed by cap-binding homolog TbEIF4E5 with TbEIF4G1 or TbEIF4G2 are implicated in post-transcriptional regulation in Trypanosoma brucei. RNA 20:1272-86
Zhong, Xuehua; Du, Jiamu; Hale, Christopher J et al. (2014) Molecular mechanism of action of plant DRM de novo DNA methyltransferases. Cell 157:1050-60
Moissiard, Guillaume; Bischof, Sylvain; Husmann, Dylan et al. (2014) Transcriptional gene silencing by Arabidopsis microrchidia homologues involves the formation of heteromers. Proc Natl Acad Sci U S A 111:7474-9
Edenberg, Ellen R; Vashisht, Ajay A; Topacio, Benjamin R et al. (2014) Hst3 is turned over by a replication stress-responsive SCF(Cdc4) phospho-degron. Proc Natl Acad Sci U S A 111:5962-7
Edenberg, Ellen R; Vashisht, Ajay; Benanti, Jennifer A et al. (2014) Rad53 downregulates mitotic gene transcription by inhibiting the transcriptional activator Ndd1. Mol Cell Biol 34:725-38
Zilio, Nicola; Codlin, Sandra; Vashisht, Ajay A et al. (2014) A novel histone deacetylase complex in the control of transcription and genome stability. Mol Cell Biol 34:3500-14
Kim, Myoung Shin; Machida, Yuka; Vashisht, Ajay A et al. (2013) Regulation of error-prone translesion synthesis by Spartan/C1orf124. Nucleic Acids Res 41:1661-8
Twu, Olivia; de Miguel, Natalia; Lustig, Gila et al. (2013) Trichomonas vaginalis exosomes deliver cargo to host cells and mediate hostýýýparasite interactions. PLoS Pathog 9:e1003482

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