UCHL3 Regulates Topoisomerase-Induced Chromosomal Break Repair by Controlling TDP1 Proteostasis

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• DNA-protein crosslinks are implicated in both cancer treatment and neurodegenerative diseases.
• Tyrosyl DNA phosphodiesterase 1 (TDP1) is crucial for repairing DNA breaks caused by topoisomerases.
• The regulatory mechanisms controlling TDP1 protein levels remain largely unknown.

Purpose of the Study:

• To elucidate the mechanism controlling tyrosyl DNA phosphodiesterase 1 (TDP1) protein levels.
• To identify the deubiquitylase responsible for TDP1 proteostasis.
• To investigate the role of UCHL3 in TDP1 regulation and its clinical implications.

Main Methods:

• Investigated TDP1 regulation through ubiquitylation assays.
• Identified UCHL3 as the key deubiquitylase controlling TDP1.
• Utilized cell-based assays to assess the impact of UCHL3 modulation on TDP1 levels and cellular response to DNA damaging agents.
• Examined UCHL3 and TDP1 expression in cancer and neurodegenerative disease models.

Main Results:

• TDP1 protein levels are regulated by ubiquitylation.
• UCHL3 was identified as the deubiquitylase that maintains TDP1 proteostasis.
• Depletion of UCHL3 led to increased TDP1 ubiquitylation and turnover, sensitizing cells to topoisomerase poisons.
• Overexpression of UCHL3 suppressed TDP1 ubiquitylation and turnover.
• TDP1 overexpression in therapy-resistant rhabdomyosarcoma correlated with UCHL3 overexpression.
• UCHL3 downregulation in spinocerebellar ataxia with axonal neuropathy (SCAN1) resulted in elevated TDP1 ubiquitylation and turnover.

Conclusions:

• UCHL3 is a critical regulator of TDP1 proteostasis.
• UCHL3 acts as a fine-tuner of protein-linked DNA break repair.
• Dysregulation of the UCHL3-TDP1 axis contributes to therapeutic resistance in cancer and pathogenesis in neurodegenerative disorders.