Protein C-terminal variations impact proteostasis

Area of Science:

• Biochemistry
• Molecular Biology
• Proteomics

Background:

• Protein C-termini exhibit variability due to errors or programmed regulation, contributing to proteome diversity.
• The precise impact of these C-terminal variations on protein stability and function is not fully understood.
• Aberrant C-termini are often associated with protein degradation, but this link may not be universal.

Purpose of the Study:

• To investigate how C-terminal variations, arising from nonstop mutations, alternative splicing, and translational readthrough, influence protein half-lives.
• To determine if disease-associated C-terminal alterations affect the stability of key proteins like oncoproteins and tumor suppressors.
• To identify features distinguishing erroneous C-termini from wild-type and understand their targeting by the ubiquitin ligase network.

Main Methods:

• Analysis of C-terminal variations derived from nonstop mutations, alternative splicing, and translational readthrough.
• Assessment of protein half-lives in response to C-terminal modifications.
• Identification of specific C-terminal features and their interaction with the ubiquitin ligase network.

Main Results:

• Contrary to previous assumptions, erroneous C-termini can either stabilize or destabilize proteins.
• Disease-relevant nonstop mutations were found to alter the stability of numerous oncoproteins and tumor suppressors.
• C-terminal variations were observed to commonly influence the stability of canonical proteins, suggesting roles beyond protein quality control.
• Hydrophobic C-termini were identified as targets for a complex ubiquitin ligase network.

Conclusions:

• C-terminal variation is a significant factor influencing protein stability and proteome diversity, with implications extending beyond protein quality control.
• Disease-associated C-terminal alterations can impact the stability of critical cancer-related proteins.
• The ubiquitin ligase network plays a role in targeting specific C-terminal features, highlighting a regulatory mechanism for protein degradation.