F Martínez-Azorín | PubMed Health

PubMed2001

A study on the human mitochondrial RNA polymerase activity points to existence of a transcription factor B-like protein.

In the present work, the RNA polymerase activity of the human mitochondrial RNA polymerase mature protein (h-mtRPOLm) is shown, and its molecular activity calculated (2.1+/-0.9 min(-1)). An activity analysis of h-mtRPOLm and deleted versions of it has demonstrated that the entire recombinant protein is required for this activity. In addition, h-mtRPOLm alone or in presence of the known mitochondrial transcription factors (human mitochondrial transcription factor A and/or human mitochondrial transcription termination factor) is not able to initiate transcription from the specific human mitochondrial promoters pointing to the existence of a human mitochondrial transcription factor B-like protein.

Base Sequence↗

PubMed1998

[Human mitochondrial genetic system].

The mitochondria are subcellular organelles devoted to energy production in form of ATP that contain their own genetic system. Mitochondrial DNA codify a small, but extremely important, number of polypeptides of the respiratory chain. The other mitochondrial proteins are encoded in the nucleus. Therefore, mitochondrial biogenesis require the coordinated expression of nuclear and mitochondrial genetic systems. The gene arrangement in mitochondrial DNA is extremely compact with the tRNA genes interspersed with the rRNA and protein-coding genes. This organization has its precise counterpart in the mode of expression and distinctive structural features of the RNAs. Both mitochondrial DNA strands are transcribed as a whole in the form of three polycistronic molecules that are later cut by specific enzymes that recognize the 5' and 3' end of the tRNA sequences, to produced the mature rRNA, mRNA and tRNA. The mitochondrial coded mRNAs are translated into proteins by a mitochondrial specific protein-synthesizing machinery. The genetics of the mitochondrial DNA differs from that of the nuclear DNA in several features. In particular, the mitochondrial genome is inherited from the mother that transmit their mitochondrial DNA to all her offsprings. Another characteristic of this genome is its tendency to mutate more frequently than the nuclear DNA. This provides a powerful tool for studying the evolution of man.

DNA, Mitochondrial↗