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Protein binding, DNA bending and mitochondrial transcription regulation

AuthorsSolà, Maria
Issue Date13-Jun-2012
Citation9th Kristineberg Symposium >Mitochondrial Molecular Biology> (2012)
AbstractMitochondrial DNA (mtDNA) regulation is performed by a few number of nuclear-coded proteins imported from the cytosol. Some of these proteins are known to have different activities on the DNA. An example is mTERF, a transcription termination factor also implicated in replication pausing and which also binds to several strategic mtDNA sites with different affinities. Another important protein is TFAM, which is essential for mitochondrial DNA packaging and maintenance and plays a crucial role in transcription. The crystal structure of these two proteins, both in complex with DNA, was determined and in both cases, the structural information suggested interesting structure-function relationships that were analysed by biochemical and biophysical approaches. Both cases present original features: mTERF in complex with a dsDNA oligonucleotide shows for the first time nine left-handed three-helical repeats that wrap smoothly around the DNA major groove. The two terminal repeats contact two distinct DNA molecules whose axes form an angle of 36 degrees, suggesting a similar bending of a continuous DNA molecule that we were able to demonstrate with studies in solution using small angle X-ray scattering (SAXS). The crystallographic analysis of TFAM in complex with an oligonucleotide containing the mitochondrial light-strand promoter (LSP) revealed also for the first time two high-mobility group (HMG) protein domains that, via different DNA-recognition properties, intercalate residues at two inverted DNA motifs inducing an overall DNA bend of ~180¿. The DNA U-turn is stabilized by the inter-domain linker which, in the absence of DNA, is highly flexible in solution. These structural properties will be discussed in light of protein function.
DescriptionComunicación presentada en el 9th Kristineberg Symposium "Mitochondrial Molecular Biology", celebrado del 13 al 16 de junio de 2012 en Kristineberg (Suecia)
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