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A novel Ras inhibitor, Eri1, engages yeast Ras at the endoplasmic reticulum
Andrew K Sobering1, Martin J Romeo, Heather A Vay
1Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland 21205, USA.
Abstract:
Ras oncoproteins are monomeric GTPases that link signals from the cell surface to pathways that regulate cell proliferation and differentiation. Constitutively active mutant forms of Ras are found in ca. 30% of human tumors. Here we report the isolation of a novel gene from Saccharomyces cerevisiae, designated ERI1 (for endoplasmic reticulum-associated Ras inhibitor 1), which behaves genetically as an inhibitor of Ras signaling. ERI1 encodes a 68-amino-acid protein that associates in vivo with GTP-bound Ras in a manner that requires an intact Ras-effector loop, suggesting that Eri1 competes for the same binding site as Ras target proteins. We show that Eri1 localizes primarily to the membrane of the endoplasmic reticulum (ER), where it engages Ras. The recent demonstration that signaling from mammalian Ras is not restricted to the cell surface but can also proceed from the cytoplasmic face of the ER suggests a regulatory function for Eri1 at that membrane.
Insights
Researchers discovered ERI1, a novel yeast gene that inhibits Ras signaling by binding to GTP-bound Ras at the endoplasmic reticulum membrane. This protein may regulate Ras activity in cellular proliferation and differentiation pathways.
Area of Science:
- Molecular biology
- Cell signaling
- Yeast genetics
Background:
- Ras oncoproteins are key regulators of cell proliferation and differentiation.
- Mutant Ras proteins are implicated in approximately 30% of human cancers.
- Ras signaling pathways are crucial for cellular functions.
Purpose of the Study:
- To identify novel regulators of Ras signaling.
- To characterize a newly discovered yeast gene, ERI1, as a potential inhibitor of Ras.
- To elucidate the mechanism and localization of ERI1's interaction with Ras.
Main Methods:
- Genetic screening in Saccharomyces cerevisiae to identify Ras signaling inhibitors.
- Gene cloning and sequencing of the novel gene ERI1.
- In vivo association studies to determine Eri1-Ras interaction.
- Subcellular localization assays using microscopy to pinpoint Eri1's location.
- Analysis of Ras-effector loop involvement in Eri1 binding.
Main Results:
- Isolation and characterization of ERI1, a novel yeast gene.
- ERI1 encodes a 68-amino-acid protein that inhibits Ras signaling.
- Eri1 physically associates with GTP-bound Ras in vivo.
- Eri1 binding requires an intact Ras-effector loop, suggesting competition with Ras targets.
- Eri1 localizes to the endoplasmic reticulum (ER) membrane and interacts with Ras there.
Conclusions:
- ERI1 acts as a novel inhibitor of Ras signaling in yeast.
- Eri1's interaction with Ras at the ER membrane suggests a regulatory role in Ras-dependent pathways.
- The findings provide insights into the localization and mechanism of Ras signal regulation.