RESUMO
Oncogene-induced senescence (OIS) is a form of stable cell-cycle arrest arising in response to oncogenic stimulation. OIS must be bypassed for transformation, but the mechanisms of OIS establishment and bypass remain poorly understood, especially at the post-transcriptional level. Here, we show that the RNA-binding protein UNR/CSDE1 enables OIS in primary mouse keratinocytes. Depletion of CSDE1 leads to senescence bypass, cell immortalization, and tumor formation, indicating that CSDE1 behaves as a tumor suppressor. Unbiased high-throughput analyses uncovered that CSDE1 promotes OIS by two independent molecular mechanisms: enhancement of the stability of senescence-associated secretory phenotype (SASP) factor mRNAs and repression of Ybx1 mRNA translation. Importantly, depletion of YBX1 from immortal keratinocytes rescues senescence and uncouples proliferation arrest from the SASP, revealing multilayered mechanisms exerted by CSDE1 to coordinate senescence. Our data highlight the relevance of post-transcriptional control in the regulation of senescence.
Assuntos
Senescência Celular/fisiologia , Proteínas de Ligação a DNA/metabolismo , Proteínas de Ligação a RNA/metabolismo , Animais , Pontos de Checagem do Ciclo Celular/genética , Pontos de Checagem do Ciclo Celular/fisiologia , Linhagem Celular , Proliferação de Células/fisiologia , Senescência Celular/genética , Proteínas de Ligação a DNA/fisiologia , Feminino , Expressão Gênica/genética , Regulação da Expressão Gênica/genética , Humanos , Queratinócitos/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Nus , Oncogenes/genética , Cultura Primária de Células , Processamento Pós-Transcricional do RNA/fisiologia , Proteínas de Ligação a RNA/fisiologia , Fenótipo Secretor Associado à Senescência/genética , Fenótipo Secretor Associado à Senescência/fisiologia , Transdução de Sinais/fisiologia , Proteína 1 de Ligação a Y-Box/metabolismoRESUMO
Many eukaryotic genes contain embedded antisense transcripts and repetitive sequences of unknown function. We report that male germline-specific expression of an antisense transcript contained in an intron of C. elegans Target of Rapamycin (TOR, let-363) is associated with (1) accumulation of endo-small interfering RNAs (siRNAs) against an embedded Helitron transposon and (2) activation of an alternative 3' splice site of TOR. The germline-specific Argonaute proteins PRG-1 and CSR-1, which participate in self/nonself RNA recognition, antagonistically regulate the generation of these endo-siRNAs, TOR mRNA levels, and 3' splice-site selection. Supply of exogenous double-stranded RNA against the region of sense/antisense overlap reverses changes in TOR expression and splicing and suppresses the progressive multigenerational sterility phenotype of prg-1 mutants. We propose that recognition of a "nonself" intronic transposon by endo-siRNAs/the piRNA system provides physiological regulation of expression and alternative splicing of a host gene that, in turn, contributes to the maintenance of germline function across generations.