CHIP promotes human telomerase reverse transcriptase degradation and negatively regulates telomerase activity

Area of Science:

• Molecular Biology
• Cell Biology
• Cancer Research

Background:

• Telomere maintenance in eukaryotes relies on telomerase, comprising telomerase reverse transcriptase (TERT) and RNA.
• Human TERT (hTERT) activity is regulated transcriptionally and post-translationally.
• Hsp90 and p23 chaperones are known to assemble active telomerase with hTERT.

Purpose of the Study:

• To investigate the role of CHIP (C-terminus of Hsc70-interacting protein) in regulating hTERT.
• To understand the mechanism by which CHIP affects telomerase activity and telomere length.
• To explore CHIP as a potential target for modulating telomerase in cancer.

Main Methods:

• Co-immunoprecipitation to detect CHIP-hTERT association.
• Western blotting to assess hTERT protein levels and degradation.
• Overexpression and knockdown experiments of CHIP.
• Analysis of hTERT nuclear translocation and p23 dissociation.
• Cell cycle analysis of CHIP-hTERT association.

Main Results:

• CHIP physically associates with hTERT in the cytoplasm, targeting it for ubiquitin-mediated degradation.
• CHIP overexpression inhibits nuclear translocation of hTERT and reduces telomerase activity.
• CHIP knockdown stabilizes cytoplasmic hTERT but does not affect nuclear hTERT, telomerase activity, or telomere length.
• CHIP and Hsp70 binding to hTERT promotes p23 dissociation, hindering nuclear translocation.
• CHIP-hTERT association peaks in G2/M phases, indicating cell cycle-dependent regulation.

Conclusions:

• CHIP modulates cellular hTERT abundance through cytoplasmic degradation.
• CHIP can remodel hTERT-chaperone complexes, influencing its localization and activity.
• CHIP represents a novel pathway for regulating telomerase activity, with implications for cancer therapy.