CNOT7 Outcompetes Its Paralog CNOT8 for Integration into The CCR4-NOT Complex

Area of Science:

• Molecular Biology
• Gene Regulation

Background:

• The CCR4-NOT deadenylase complex regulates eukaryotic gene expression post-transcriptionally.
• CNOT7 and CNOT8 are highly similar vertebrate homologs of yeast Caf1, a catalytic subunit.

Purpose of the Study:

• To investigate the distinct physiological functions and regulatory interactions between CNOT7 and CNOT8 within the CCR4-NOT complex.
• To elucidate the non-reciprocal regulatory relationship between CNOT7 and CNOT8.

Main Methods:

• Analysis of CNOT7 and CNOT8 protein and mRNA levels in knockout and knockdown models.
• Assessment of protein stability and binding affinities within the CCR4-NOT complex.
• Investigating the impact of CNOT7 depletion on CNOT8 stability and complex incorporation.

Main Results:

• CNOT7 depletion increases CNOT8 protein levels without affecting CNOT8 mRNA, while CNOT7 levels remain unchanged upon CNOT8 loss.
• CNOT7 exhibits higher affinity for CNOT1 than CNOT8, inhibiting CNOT8 binding.
• CNOT7 depletion enhances CNOT8 incorporation into the CCR4-NOT complex and increases CNOT8 protein stability.

Conclusions:

• CNOT7 is the dominant paralog in the CCR4-NOT complex, exerting non-reciprocal control over CNOT8.
• CNOT7 and CNOT8 protein stability are regulated distinctly, highlighting their unique roles in gene expression.
• The CCR4-NOT complex may directly regulate CNOT8 expression, with CNOT7 playing a crucial role in this process.