TCTP and CSN4 control cell cycle progression and development by regulating CULLIN1 neddylation in plants and animals

Area of Science:

• Molecular Biology
• Cell Biology
• Developmental Biology

Background:

• Translationally Controlled Tumor Protein (TCTP) is crucial for cell cycle regulation.
• The COP9 Signalosome (CSN) complex, specifically CSN4, influences CULLIN-RING ubiquitin ligases activity via CULLIN neddylation.
• The precise interaction linking TCTP to CSN function in cell cycle control was previously unknown.

Purpose of the Study:

• To elucidate the molecular mechanism by which TCTP regulates the G1/S transition.
• To identify the interaction partner of TCTP involved in cell cycle control.
• To investigate the conserved role of TCTP and CSN4 in cell proliferation across different species.

Main Methods:

• Genetic interaction studies in Arabidopsis and tobacco cells.
• Downregulation experiments of TCTP and CSN4.
• Analysis of CULLIN 1 (CUL1) neddylation status.
• Comparative studies in Drosophila melanogaster.

Main Results:

• TCTP interacts with CSN4, a subunit of the COP9 Signalosome.
• Downregulation of CSN4 in plants phenocopies TCTP downregulation, delaying the G1/S transition.
• Loss-of-function of AtTCTP increases deneddylated CUL1, indicating interference with COP9 function.
• Knockdown of dCSN4 or dTCTP in Drosophila shows similar defects in cell proliferation and CUL1 neddylation, confirming a conserved mechanism.

Conclusions:

• CSN4 is identified as the missing link connecting TCTP to the regulation of cell cycle progression and cell proliferation.
• The TCTP-CSN4 interaction represents a conserved mechanism essential for organ development in both plants and animals.
• This discovery opens new avenues for understanding TCTP's role in development and associated disorders.