Posted: January 8, 2010

Micro RNAs make genes shut up

(Nanowerk News) RNA molecules are the mobile messengers of genes. They carry information on the production of proteins from the DNA to the ribosomes. In addition to these messenger RNAs all living beings have micro RNAs that can hinder the messenger RNAs and thus the production of proteins. Biologists at the University of Freiburg, Germany, around Lecturer Dr. Wolfgang Frank und Professor Dr. Ralf Reski from the Chair Plant Biotechnology have discovered that such micro RNAs also come into direct contact with genes, effectively turning off the genes in the process. Their findings have now been published in the current issue of the scientific journal CELL ("Transcriptional Control of Gene Expression by MicroRNAs").
With the exception of some viruses all living beings store their hereditary information, the sum of all their genes, as DNA. Active genes are transcribed into messenger RNAs (mRNAs) that function as blueprints for the production of proteins on ribosomes. Inactive genes are not transcribed into mRNAs. The fine balance between switched-on and switched-off genes differs between organs and changes during development and under varying environmental conditions. When this balance is disturbed disfiguration and illnesses such as cancer occur. In 2006 the American biologists Mello & Fire were awarded the Nobel Prize for their discovery that minute RNA molecules in the worm C. elegans can attach themselves to mRNAs und thus hinder their translation into proteins.
The biologists in Freiburg together with researchers from the Max-Planck-Institute for Developmental Biology in Tuebingen have now described how microRNAs not only indirectly turn off genes by obstructing mRNAs, but can also turn off genes directly. In the process the genes are silenced chemically by adding methyl groups. In the world of Biology such changes are termed as Epigenetics.
The researchers at the Freiburg Chair Plant Biotechnology have found this novel mechanism for gene regulation in their favoured object of research, the moss Physcomitrella patens.
Besides Dr. Frank and Prof. Reski, Dr. Basel Khraiwesh, M. Asif Arif, Dr. Gotelinde I. Seumel from Freiburg, and Stephan Ossowski and Prof. Detlef Weigel from the MPI Tuebingen were involved in this study.
When the biologists in Freiburg created so called knockout-mosses, they were surprised by the effect because it contradicted all existing expectations. Now they suspect that their newly discovered mechanism for gene regulation occurs not only in moss, but also in many other life forms, including us humans.
Source: Albert-Ludwigs-Universit├Ąt Freiburg