RESUMO
Specialized proteins known as molecular chaperones bind transiently to non-native conformational states of proteins and protein complexes to promote transition to a biologically active conformation. Recently, it was demonstrated in vitro that proteins do not uniquely possess this activity. We show that mitochondrial 12S and 16S ribosomal RNA can fold chemically denatured proteins and reactivate heat-induced aggregated proteins in vitro. This chaperone action is ATP-independent. The specific secondary structure of the mitochondrial rRNA is critical to its folding activity. Furthermore, mutant mitochondrial 16S rRNA from aged cardiac muscle cells lacked this activity. We propose that mitochondrial 12S and 16S ribosomal RNA may play an important role in protein folding in mitochondria.
Assuntos
Desoxirribonuclease EcoRI/metabolismo , Enzimas/metabolismo , Dobramento de Proteína , RNA Ribossômico 16S/metabolismo , RNA Ribossômico/metabolismo , RNA/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Besouros , DNA Mitocondrial/genética , RNA Polimerases Dirigidas por DNA/química , RNA Polimerases Dirigidas por DNA/metabolismo , Desoxirribonuclease EcoRI/química , Enzimas/química , Humanos , Cinética , Luciferases/química , Luciferases/metabolismo , Malato Desidrogenase/química , Malato Desidrogenase/metabolismo , Camundongos , Mitocôndrias Cardíacas/enzimologia , Chaperonas Moleculares/metabolismo , Conformação de Ácido Nucleico , Desnaturação Proteica , RNA/química , RNA Mitocondrial , RNA Ribossômico/química , RNA Ribossômico 16S/química , Suínos , Transcrição Gênica , Proteínas ViraisRESUMO
Overexpression of the transcription factor YY1 activates DNA synthesis in differentiated primary human coronary artery smooth muscle cells. Overexpression of the retinoblastoma protein together with YY1 blocked this effect. In growth-arrested cells, YY1 resides in a complex with the retinoblastoma protein, but the complex is not detected in serum-stimulated S phase cultures, indicating that the interaction of the retinoblastoma protein and YY1 is cell cycle-regulated. Recombinant retinoblastoma protein directly interacts with YY1, destabilizing the interaction of YY1 with DNA and inhibiting its transcription initiator function in vitro. We conclude that in differentiated cells elevation of the nuclear level of YY1 protein favors progression into the S phase, and we propose that this activity is regulated by its interaction with the retinoblastoma protein.
