Journal
MOLECULAR AND CELLULAR BIOLOGY
Volume 23, Issue 23, Pages 8668-8690Publisher
AMER SOC MICROBIOLOGY
DOI: 10.1128/MCB.23.23.8668-8690.2003
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Funding
- NCI NIH HHS [R01-CA82599, R01 CA082599, R01 CA080000, R01-CA80000] Funding Source: Medline
- NIEHS NIH HHS [R01 ES009169, R01-ES09169] Funding Source: Medline
- NATIONAL CANCER INSTITUTE [R01CA082599, R01CA080000] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES [R01ES009169] Funding Source: NIH RePORTER
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Telomerase, an enzyme that maintains telomere length, plays major roles in cellular immortalization and cancer progression. We found that an exogenous BRCA1 gene strongly inhibited telomerase enzymatic activity in human prostate and breast cancer cell lines and caused telomere shortening in cell lines expressing wild-type BRCA1 (wtBRCA1) but not a tumor-associated mutant BRCA1 (T300G). wtBRCA1 inhibited the expression of the catalytic subunit (telomerase reverse transcriptase [TERT]) but had no effect on the expression of a subset of other components of the telomerase holoenzyme or on the expression of c-Myc, a transcriptional activator of TERT. However, endogenous BRCA1 associated and partially colocalized with c-Myc; exogenous wtBRCA1 strongly suppressed TERT promoter activity in various cell lines. The TERT inhibition was due, in part; to suppression of c-Myc E-box-mediated transcriptional activity. Suppression of TERT promoter and c-Myc activity required the amino terminus of BRCA1 but not the carboxyl terminus. Finally, endogenous BRCA1 and c-Myc were detected on transfected mouse and human TERT promoter segments in vivo. We postulate that inhibition of telomerase may contribute to the BRCA1 tumor suppressor activity.
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