RESUMO
Cellular senescence is a phenomenon of irreversible growth arrest in mammalian somatic cells in culture. Various stresses induce cellular senescence and indeed, we have found that excess thymidine effectively induces cellular senescence in human cells. Further, many reports indicate the implication of chromatin proteins in cellular senescence. Here we analysed the role of lamin B receptor (LBR), a nuclear envelope protein that regulates heterochromatin organization, in cellular senescence induced by excess thymidine. We then found that the LBR protein was down-regulated and showed aberrant localization in cells upon induction of cellular senescence by excess thymidine. Additionally, we also found that knock-down of LBR facilitated the induction of cellular senescence by excess thymidine in cancerous HeLa cells, and importantly, it induced cellular senescence in normal human diploid fibroblast TIG-7 cells. These results suggested that decreased LBR function is involved in the induction of cellular senescence in human cells.
Assuntos
Senescência Celular/fisiologia , Receptores Citoplasmáticos e Nucleares/metabolismo , Bromodesoxiuridina/farmacologia , Senescência Celular/genética , Dano ao DNA/efeitos dos fármacos , Replicação do DNA/efeitos dos fármacos , Técnicas de Silenciamento de Genes , Células HeLa , Heterocromatina/metabolismo , Humanos , Lamina Tipo B/metabolismo , Membrana Nuclear/metabolismo , Receptores Citoplasmáticos e Nucleares/genética , Timidina/farmacologia , Receptor de Lamina BRESUMO
5-Bromodeoxyuridine (BrdU), a thymidine analogue, induces cellular senescence in mammalian cells. BrdU induces cellular senescence probably through the regulation of chromatin because BrdU destabilizes or disrupts nucleosome positioning and decondenses heterochromatin. Since heterochromatin is tethered to the nuclear periphery through the interaction with the nuclear envelope proteins, we examined the localization of the several nuclear envelope proteins such as lamins, lamin-interacting proteins, nuclear pore complex proteins, and nuclear transport proteins in senescent cells. We have shown here that lamin B receptor (LBR) showed a change in localization in both BrdU-induced and replicative senescent cells.
Assuntos
Senescência Celular/fisiologia , Laminas/metabolismo , Membrana Nuclear/metabolismo , Membrana Nuclear/ultraestrutura , Receptores Citoplasmáticos e Nucleares/metabolismo , Bromodesoxiuridina/farmacologia , Células HeLa , Humanos , Frações Subcelulares/efeitos dos fármacos , Frações Subcelulares/metabolismo , Distribuição Tecidual/efeitos dos fármacos , Receptor de Lamina BRESUMO
Excess thymidine induces unbalanced growth by delaying DNA replication and subsequently induces senescence in every human cell type. Our previous studies with use of inhibitors suggested that ERK1/2 has a major role in these processes. Here we directly assessed the roles of ERK1 and ERK2 in unbalanced growth induced by excess thymidine. Knockdown of ERK2 and ERK1 by vector-based RNA interference prevented loss of colony forming ability and appearance of senescence markers induced by excess thymidine in HeLa and TIG-7 cells, respectively. Such cells continued growing in the presence of excess thymidine. Double knockdown of ERK1 and ERK2 did not improve the effects of single knockdowns of ERK1 and ERK2 in either cell types. These results demonstrate that ERK1 or ERK2 has a major role in manifestation of unbalanced growth in human cells.
