Tuesday, March 13, 2012

Double life of mitochondrial ribosomal protein L7 12

Mitochondria have their own transcriptional and translational apparatus, even though they produce only a handful of proteins, therefore most of the proteins are imported from the cytoplasm. Trancription, translation and protein insertion into the membrane are interconnected: translational activators regulating mitochondrial translation are interacting with mitochondrial RNA polymerase via Nam1p and Sls1p proteins (Bryan et al. Genetics 2002), Puf proteins connect cytoplasmic translation and protein import into mitochondria by direct interaction with Tom20 subunit of the TOM protein import channel (Saint-Georges et al. PLoS ONE 2008).

But this seems not tight enough interaction for mitochondrial translation and transcription. It turnes out what mitohondrial ribosomal protein L7 12 (the one that brings translational GTPases to the ribosome), has a double life. Apart from doing its normal job as a part of the ribosome, it doubles as a transctiptional factor, selectively associating with human mitochondrial RNA polymerase and activating it (Surovtseva et al. PNAS 2011). And as if it is not enough, there are several paralogues of L7 12 in mitochondria, both in plants (Delage et al. Biochimie 2007) and in mammals (Koc et al. JBC 2001). 

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