RESUMEN
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.
Asunto(s)
Senescencia Celular/fisiología , Proteínas de Unión al ADN/metabolismo , Proteínas de Unión al ARN/metabolismo , Animales , Puntos de Control del Ciclo Celular/genética , Puntos de Control del Ciclo Celular/fisiología , Línea Celular , Proliferación Celular/fisiología , Senescencia Celular/genética , Proteínas de Unión al ADN/fisiología , Femenino , Expresión Génica/genética , Regulación de la Expresión Génica/genética , Humanos , Queratinocitos/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Desnudos , Oncogenes/genética , Cultivo Primario de Células , Procesamiento Postranscripcional del ARN/fisiología , Proteínas de Unión al ARN/fisiología , Fenotipo Secretor Asociado a la Senescencia/genética , Fenotipo Secretor Asociado a la Senescencia/fisiología , Transducción de Señal/fisiología , Proteína 1 de Unión a la Caja Y/metabolismoRESUMEN
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.
