Structure of a molecular copy machine: How mitochondrial genes are transcribed

Sep 26, 2011

Mitochondria are compartments within cells and have their own DNA. The key protein required for the expression of the genetic information in this DNA is the mitochondrial RNA polymerase enzyme. Its three-dimensional structure has now been determined in atomic detail.

The mitochondria are the cell's power stations. In , they supply energy in usable form by converting nutrients into the universal energy currency of the cell, adenosine triphosphate (). Mitochondria possess their own DNA, and are inherited via the . The mitochondrial DNA codes for a small number of proteins that are essential for in the organelle. The first step in the decoding of this is the synthesis, or transcription, of RNA copies of the DNA by the enzyme mitochondrial RNA polymerase. The are then used to program . However, exactly how the mitochondrial RNA polymerase actually works has not been clear, as its structure was unknown – until now.

Biochemist Professor Patrick Cramer, Director of the Gene Center at LMU, in collaboration with Professor Dmitry Temiakov of the University of Medicine and Dentistry of New Jersey (USA), has now determined the architecture of this molecular copy machine. "With the help of a synchrotron as a source of radiation and using the method of X-ray diffraction, we were able to determine the first three-dimensional structure of a human polymerase, the mitochondrial RNA polymerase, in atomic detail," Cramer explains.

Interestingly, the structure shows a certain resemblance to those of the RNA polymerases found in so-called phages. Phages are viruses that specifically attack bacteria and can insert their genomes into those of their bacterial hosts. It is now generally accepted that mitochondria evolved from free-living bacteria that were engulfed by the progenitor of today's animal cells at an early stage in evolution. The similarities observed between the RNA polymerases of mitochondria and phages provide new insights into the evolution of the organelle and its genome. It appears that, in the course of evolution, a phage polymerase gene developed the ability to transcribe the genes in the .

The structure also provides several hints as to how this molecular copy machine functions. "In particular, the structure explains why two other protein factors are necessary to enable the RNA polymerase to bind at the right site on the DNA, and to transcribe the genetic information from this location," says Cramer. The new results represent a significant first step in understanding the function and regulation of the human mitochondrial genome. And this is not just of academic interest: Some drugs used to treat viral infections, such as hepatitis C, have major side-effects, apparently because they inhibit not only the viral polymerase, but also the mitochondrial RNA polymerase of the host cell. The researchers now hope that their new data can help in the design of antiviral drugs that are better tolerated.

Explore further: Fighting bacteria—with viruses

More information: Structure of human mitochondrial RNA polymerase, R. Ringel, M. Sologub, Y.I. Morozov, D. Litonin, P. Cramer, D. Temiakov, Nature online 25.09.2011. DOI: 10.1038/nature10435

Provided by Ludwig-Maximilians-Universitat Munchen

5 /5 (1 vote)
add to favorites email to friend print save as pdf

Related Stories

How RNA polymerase II gets the go-ahead for gene transcription

Oct 09, 2009

All cells perform certain basic functions. Each must selectively transcribe parts of the DNA that makes up its genome into RNAs that specify the structure of proteins. The set of proteins synthesized by a cell in turn determines ...

Researchers reveal a new mechanism of genomic instability

Aug 18, 2011

Researchers at NYU School of Medicine have discovered the cellular mechanisms that normally generate chromosomal breaks in bacteria such as E. coli. The study's findings are published in the August 18 issue of the journal ...

Recommended for you

Fighting bacteria—with viruses

Jul 24, 2014

Research published today in PLOS Pathogens reveals how viruses called bacteriophages destroy the bacterium Clostridium difficile (C. diff), which is becoming a serious problem in hospitals and healthcare institutes, due to its re ...

Atomic structure of key muscle component revealed

Jul 24, 2014

Actin is the most abundant protein in the body, and when you look more closely at its fundamental role in life, it's easy to see why. It is the basis of most movement in the body, and all cells and components ...

Brand new technology detects probiotic organisms in food

Jul 23, 2014

In the food industr, ity is very important to ensure the quality and safety of products consumed by the population to improve their properties and reduce foodborne illness. Therefore, a team of Mexican researchers ...

Protein evolution follows a modular principle

Jul 23, 2014

Proteins impart shape and stability to cells, drive metabolic processes and transmit signals. To perform these manifold tasks, they fold into complex three-dimensional shapes. Scientists at the Max Planck ...

Report on viruses looks beyond disease

Jul 22, 2014

In contrast to their negative reputation as disease causing agents, some viruses can perform crucial biological and evolutionary functions that help to shape the world we live in today, according to a new report by the American ...

User comments : 0