RESUMO
Human telomerase reverse transcriptase (hTERT) plays a central role in telomere lengthening for continuous cell proliferation, but it remains unclear how extracellular cues regulate telomerase lengthening of telomeres. Here we report that the cytokine bone morphogenetic protein-7 (BMP7) induces the hTERT gene repression in a BMPRII receptor- and Smad3-dependent manner in human breast cancer cells. Chonic exposure of human breast cancer cells to BMP7 results in short telomeres, cell senescence and apoptosis. Mutation of the BMPRII receptor, but not TGFbRII, ACTRIIA or ACTRIIB receptor, inhibits BMP7-induced repression of the hTERT gene promoter activity, leading to increased telomerase activity, lengthened telomeres and continued cell proliferation. Expression of hTERT prevents BMP7-induced breast cancer cell senescence and apoptosis. Thus, our data suggest that BMP7 induces breast cancer cell aging by a mechanism involving BMPRII receptor- and Smad3-mediated repression of the hTERT gene.
Assuntos
Feminino , Humanos , Proteína 2 Relacionada a Actina , Genética , Metabolismo , Receptores de Activinas Tipo II , Genética , Metabolismo , Proteína Morfogenética Óssea 7 , Genética , Metabolismo , Receptores de Proteínas Morfogenéticas Ósseas Tipo II , Genética , Metabolismo , Neoplasias da Mama , Genética , Metabolismo , Senescência Celular , Células HeLa , Células MCF-7 , Proteínas de Neoplasias , Genética , Metabolismo , Proteínas Serina-Treonina Quinases , Genética , Metabolismo , Receptor do Fator de Crescimento Transformador beta Tipo II , Receptores de Fatores de Crescimento Transformadores beta , Genética , Metabolismo , Proteína Smad3 , Genética , Metabolismo , Telomerase , Genética , Metabolismo , Homeostase do TelômeroRESUMO
Telomere assumes intra-molecular G-quadruplex that is a significant drug target for inhibiting telomerase maintenance of telomeres in cancer. Metal cations have been recognized as playing important roles in stabilizing G-quadruplex, but their binding processes to human telomeric G-quadruplex remain uncharacterized. To investigate the detailed binding procedures, molecular dynamics simulations were conducted on the hybrid [3 + 1] form-one human telomeric intra-molecular G-quadruplex. We show here that the binding of a potassium ion to a G-tetrad core is mediated by two alternative pathways. Principal component analysis illustrated the dominant concerted motions of G-quadruplex occurred at the loop domains. MM-PBSA calculations revealed that binding was energetically favorable and driven by the electrostatic interactions. The lower binding site was found more constructive favorable for binding. Our data provide useful information on a potassium-mediated stable structure of human telomeric intra-molecular G-quadruplex, implicating in ion disorder associated conformational changes and targeted drug design.