Dissecting OGT's TPR domain to identify determinants of cellular function

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• O-GlcNAc transferase (OGT) is a crucial mammalian enzyme involved in protein glycosylation and cell cycle regulation.
• OGT's tetratricopeptide repeat (TPR) domain is vital for substrate recognition, but its specific role in cellular functions remains unclear.

Purpose of the Study:

• To investigate how modifications to OGT's TPR domain impact cell growth and homeostasis.
• To identify the essential components of the TPR domain for OGT's function and viability.

Main Methods:

• Endogenous OGT deletion followed by expression of altered OGT variants.
• Analysis of cell growth rates, subcellular localization, glycosylation activity, and protein-protein interactions.

Main Results:

• Disrupting TPR residues for OGT dimerization accelerated cell growth.
• Truncating the TPR domain slowed cell growth, with eight TPRs being essential for viability.
• A viable OGT truncation variant (OGT-8) showed mislocalization, reduced glycosylation activity, and attenuated protein interactions.

Conclusions:

• OGT's N-terminal TPRs are not essential for cell viability but are crucial for proper localization and mediating protein interactions.
• The identified viable OGT truncation variant offers a tool to study OGT's essential functions.