Transcript regulation of human telomerase reverse transcriptase by c-myc and mad1

Area of Science:

• Molecular Biology
• Cancer Research
• Gene Regulation

Background:

• Telomerase activity is elevated in most cancers, with human telomerase reverse transcriptase (hTERT) being the rate-limiting component.
• hTERT expression is primarily controlled by transcript regulation, with c-myc and mad1 identified as key regulatory factors.

Purpose of the Study:

• To investigate the distinct roles of c-myc and mad1 in regulating hTERT transcription.
• To explore the impact of c-myc and mad1 on both wild-type and mutated hTERT promoters in cancer cells versus normal cells.

Main Methods:

• Construction of c-myc and mad1 eukaryotic expression vectors.
• Co-transfection of these vectors with wild-type (Tw) or double-mutated (Td) hTERT promoter luciferase reporter plasmids into T24, EJ bladder cancer cells, and normal fibrocytes.
• Measurement of luciferase activity to assess promoter activity and gene expression.

Main Results:

• Wild-type hTERT promoter (Tw) showed significant activation in bladder cancer cells (T24, EJ) but not in normal fibrocytes.
• c-myc positively regulated Tw transcript in a dose-dependent manner, while mad1 had a negative effect.
• The regulatory effects of c-myc and mad1 on the mutated promoter (Td) were reversed.
• Combined c-myc and mad1 downregulated Tw but not Td.
• Differential regulation of hTERT by c-myc and mad1 was observed in hTERT-positive cancer cells, distinct from normal cells.

Conclusions:

• c-myc and mad1 exhibit distinct regulatory mechanisms on hTERT transcription in cancer cells.
• These transcription factors modulate hTERT expression differently depending on the promoter sequence (wild-type vs. mutant).
• The findings provide potential insights into telomerase-related mechanisms driving carcinogenesis.