RESUMO
Estrogens, in particular 17ß-estradiol, are well-known regulators of essential cellular functions; however, discrepancies remain over the mechanisms by which they act on mitochondria. Here we propose a novel mechanism for the direct regulation of mitochondrial gene expression by estrogen under metabolic stress. We show that in serum-depleted medium, estrogen stimulates a rapid relocation of estrogen receptor-α to mitochondria, in which it elicits a cellular response, resulting in an increase in mitochondrial RNA abundance. Mitochondrial RNA levels are regulated through the association of estrogen receptor-α with 17ß-hydroxysteroid dehydrogenase 10, a multifunctional protein involved in steroid metabolism that is also a core subunit of the mitochondrial ribonuclease P complex responsible for the cleavage of mitochondrial polycistronic transcripts. Processing of mitochondrial transcripts affects mitochondrial gene expression by controlling the levels of mature RNAs available for translation. This work provides the first mechanism linking RNA processing and estrogen activation in mitochondrial gene expression and underscores the coordinated response between the nucleus and mitochondria in response to stress.
Assuntos
3-Hidroxiacil-CoA Desidrogenases/metabolismo , Receptor alfa de Estrogênio/metabolismo , Estrogênios/metabolismo , Regulação da Expressão Gênica/genética , Mitocôndrias/metabolismo , 3-Hidroxiacil-CoA Desidrogenases/biossíntese , 3-Hidroxiacil-CoA Desidrogenases/genética , Linhagem Celular Tumoral , Estradiol/metabolismo , Receptor alfa de Estrogênio/biossíntese , Receptor alfa de Estrogênio/genética , Genes Mitocondriais/genética , Humanos , Células MCF-7 , Mitocôndrias/enzimologia , Mitocôndrias/genética , Interferência de RNA , RNA Interferente PequenoRESUMO
Mammalian mitochondrial DNA is transcribed as precursor polycistronic transcripts containing 13 mRNAs, 2 rRNAs, punctuated by 22 tRNAs. The mechanisms involved in the excision of mitochondrial tRNAs from these polycistronic transcripts have remained largely unknown. We have investigated the roles of ELAC2, mitochondrial RNase P proteins 1 and 3, and pentatricopeptide repeat domain protein 1 in the processing of mitochondrial polycistronic transcripts. We used a deep sequencing approach to characterize the 5' and 3' ends of processed mitochondrial transcripts and provide a detailed map of mitochondrial tRNA processing sites affected by these proteins. We show that MRPP1 and MRPP3 process the 5' ends of tRNAs and the 5' unconventional, non tRNA containing site of the CO1 transcript. By contrast, we find that ELAC2 and PTCD1 affect the 3' end processing of tRNAs. Finally, we found that MRPP1 is essential for transcript processing, RNA modification, translation and mitochondrial respiration.