SUMO Protease SMT7 Modulates Ribosomal Protein L30 and Regulates Cell-Size Checkpoint Function

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Cell proliferation requires coordination of growth and division for size homeostasis.
• Mechanisms controlling cell size are not fully understood.
• Defects in SMT7 (suppressor of mat3-7) impact cell division and size in the Chlamydomonas mat3-4 mutant.

Purpose of the Study:

• To investigate the role of SMT7 in cell division and size control.
• To characterize SMT7 as a SUMO protease.
• To identify SMT7 targets involved in cell division regulation.

Main Methods:

• Development of an in vitro SUMOylation system using Chlamydomonas components.
• Assessing the SUMO protease activity of SMT7.
• Identifying and characterizing SMT7 target proteins, specifically RPL30.

Main Results:

• SMT7 was confirmed as a bona fide SUMO protease essential for regulating mitotic divisions in mat3-4 cells.
• RIBOSOMAL PROTEIN L30 (RPL30) was identified as a key SMT7 target.
• Loss of SMT7 led to increased SUMOylated RPL30, decreased mitotic divisions, and increased cell size.

Conclusions:

• SMT7 regulates cell division and size in the Chlamydomonas mat3-4 mutant through its SUMO protease activity.
• SUMOylation of RPL30 by SMT7 is crucial for controlling cell division.
• Protein SUMOylation plays a significant role in regulating fundamental cellular processes like cell division.