Regulated proteolysis by the ubiquitin-proteasome system (ubiquitin system) plays essential roles in a multitude of biological processes and has major ramifications for human health and disease, including illnesses that range from cancer and neurodegeneration to cardiovascular syndromes and defects of immunity. Our studies of the ubiquitin system and the ubiquitin-dependent N-end rule pathway over the last three decades were made possible, to a large extent, by the present grant (GM031530), currently in its 33rd year of support. The N-end rule pathway recognizes proteins containing N-terminal degradation signals called N-degrons, polyubiquitylates these proteins and thereby causes their degradation by the proteasome. Recognition components of the N-end rule pathway are called N-recognins. In eukaryotes, N-recognins are E3 ubiquitin ligases that can target N-degrons. The N-end rule pathway consists of two major branches. The first branch, called the Arg/N-end rule pathway, targets specific unacetylated N-terminal residues of protein substrates. This branch, discovered by our laboratory in 1986, continues to be a fount of biological insights and remains a focus of our studies. The other branch, called the Ac/N-end rule pathway, was discovered by our laboratory in 2010. This pathway recognizes proteins that bear N-terminally acetylated residues. Our recent (2014) study has revealed a specific complementarity (functional coupling) between the Arg/N-end rule and Ac/N-end rule pathways. The present (GM031530) renewal application focuses on this physiologically important coupling as well as the Ac/N-end rule pathway itself. The proposed projects include both functional and mechanistic studies of specific physiological substrates of the mammalian (mouse) Ac/N-end rule pathway, including Rgs2 (a regulator of signal transduction) and Aanat (serotonin N-acetyltransferase, a key circadian enzyme). These studies also include a detailed dissection of the targeting specificity of both previously identified and recently discovered N-recognins of the N-end rule pathway, including Not4, Doa10, and Ubr1 in the yeast Saccharomyces cerevisiae as well as the larger set of mammalian (mouse) counterparts of yeast N-recognins. The proposed studies will advance the understanding of the N-end rule pathway, a multifunctional, highly regulated, universally present and medically significant biological system.

Public Health Relevance

Studies proposed in this renewal application for the GM031530 grant will address the regulated protein degradation in mammalian cells. Inborn or acquired defects in proteolytic systems, which include the ubiquitin system, are a major cause of many human diseases, including cancer, infections, cardiovascular illnesses and neurodegenerative syndromes. Understanding the functions and mechanisms of the ubiquitin- dependent N-end rule pathway, a focus of the proposed studies, will contribute to advances in fundamental biology, and is also likely to lead to better therapies for specific medical problems, including currently intractable ones.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM031530-34
Application #
8813756
Study Section
Membrane Biology and Protein Processing Study Section (MBPP)
Program Officer
Gerratana, Barbara
Project Start
1992-07-01
Project End
2019-05-31
Budget Start
2015-06-01
Budget End
2016-05-31
Support Year
34
Fiscal Year
2015
Total Cost
Indirect Cost
Name
California Institute of Technology
Department
Type
Schools of Arts and Sciences
DUNS #
009584210
City
Pasadena
State
CA
Country
United States
Zip Code
91125
Kim, Jeong-Mok; Seok, Ok-Hee; Ju, Shinyeong et al. (2018) Formyl-methionine as an N-degron of a eukaryotic N-end rule pathway. Science 362:
Chen, Shun-Jia; Wu, Xia; Wadas, Brandon et al. (2017) An N-end rule pathway that recognizes proline and destroys gluconeogenic enzymes. Science 355:
Oh, Jang-Hyun; Chen, Shun-Jia; Varshavsky, Alexander (2017) A reference-based protein degradation assay without global translation inhibitors. J Biol Chem 292:21457-21465
Oh, Jang-Hyun; Hyun, Ju-Yeon; Varshavsky, Alexander (2017) Control of Hsp90 chaperone and its clients by N-terminal acetylation and the N-end rule pathway. Proc Natl Acad Sci U S A 114:E4370-E4379
Wadas, Brandon; Piatkov, Konstantin I; Brower, Christopher S et al. (2016) Analyzing N-terminal Arginylation through the Use of Peptide Arrays and Degradation Assays. J Biol Chem 291:20976-20992
Liu, Yu-Jiao; Liu, Chao; Chang, ZeNan et al. (2016) Degradation of the Separase-cleaved Rec8, a Meiotic Cohesin Subunit, by the N-end Rule Pathway. J Biol Chem 291:7426-38
Wadas, Brandon; Borjigin, Jimo; Huang, Zheping et al. (2016) Degradation of Serotonin N-Acetyltransferase, a Circadian Regulator, by the N-end Rule Pathway. J Biol Chem 291:17178-96
Piatkov, Konstantin I; Vu, Tri T M; Hwang, Cheol-Sang et al. (2015) Formyl-methionine as a degradation signal at the N-termini of bacterial proteins. Microb Cell 2:376-393
Park, Sang-Eun; Kim, Jeong-Mok; Seok, Ok-Hee et al. (2015) Control of mammalian G protein signaling by N-terminal acetylation and the N-end rule pathway. Science 347:1249-1252
Varshavsky, Alexander (2014) Discovery of the biology of the ubiquitin system. JAMA 311:1969-70

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