Novel, activated RAS mutations alter protein-protein interactions

Area of Science:

• Molecular Biology
• Yeast Genetics
• Cell Signaling

Background:

• RAS proteins are key regulators of cellular signaling pathways.
• Activating mutations in RAS genes can lead to uncontrolled cell growth.
• Understanding RAS2 function and regulation is crucial for deciphering cellular processes.

Purpose of the Study:

• To identify and characterize activating mutations in the RAS2 gene of Saccharomyces cerevisiae.
• To investigate how these mutations affect the interactions of RAS2 with its regulatory and effector proteins.
• To elucidate the molecular mechanisms underlying RAS2 activation.

Main Methods:

• Screening of random RAS2 mutants in yeast for activating traits.
• Identification and characterization of 69 distinct mutations affecting 44 amino acid residues.
• In vivo interaction assays of mutant RAS2 proteins with adenylate cyclase, RAF, CDC25, IRA2, and NF1.

Main Results:

• Nearly all activated RAS2 mutants showed enhanced interaction with adenylate cyclase and RAF.
• Some mutations reduced RAS2 affinity for guanine nucleotides, increasing nucleotide-free RAS2 fraction and CDC25 affinity.
• Mutations affecting affinity for GTPase activating proteins were identified both within and outside the switch I/II domain.

Conclusions:

• RAS2 activation involves complex alterations in protein-protein interactions and nucleotide binding.
• The study provides insights into how specific amino acid substitutions modulate RAS2 function.
• Findings contribute to a deeper understanding of RAS signaling and its regulation.