A double punch for female survival
Achieving equality between the sexes can be a challenge even for single cells. Since evolution began removing bits of male DNA to create the "Y" chromosome, males have had a single copy of certain key genes on the X chromosome, whereas females have two. Normally this would lead females to produce twice the amount of some proteins, which could be fatal, but cells have developed ways to prevent this. Researchers at the European Molecular Biology Laboratory (EMBL) in Heidelberg have now made a breakthrough in understanding how this balance, called "dosage compensation," is maintained. They have discovered a unique double-locking mechanism which prevents the production of a molecule that would be fatal for female cells; their work is reported in the current issue of Cell.
Genes are used to create mRNA molecules, which are then used to create proteins. "Cells build a machine called a ribosome on an mRNA to transform its information into proteins," Hentze says. "Weve known that a protein in female flies called SXL can block the work of this machine, but we didnt know how. This study unravels how SXL prevents the synthesis of another protein, called MSL-2, which is essential in males but would kill female flies."
An mRNA molecule is linear, with a protein-encoding part sandwiched in the middle between regulatory regions near the head and the tail. Most research has focused on interactions between the head region and the ribosome, because it is here that cells assemble a "docking bridge" for the protein-synthesis machinery. Scientists have discovered other cases where protein synthesis is blocked at this head region. But this case turned out to be different. "Copies of SXL have to be attached to both ends of the msl-2 mRNA to efficiently stop the synthesis of MSL-2 proteins," says Karsten Beckmann, a PhD student in Hentzes lab, who headed the current project.
"To our surprise we found that the SXL molecules bound at the two ends do not directly work together, but that they help each other by acting on two separate steps. The SXL that binds to the tail of the mRNA blocks the construction of the docking bridge for the ribosome at the head end." The second copy of SXL has a different function, he says. Single control mechanisms are often "leaky", which means that ribosomes may still succeed in binding to the mRNA. These ribosomes have to be stopped, and the extra copy of SXL at the head regulatory region prevents them from negotiating their way towards the protein-encoding region in the middle.
Whats unusual is that SXL is serving as its own "backup". The work by Hentze and his colleagues shows for the first time that a single regulatory molecule can deliver a "double punch" to lock away the mRNA from the ribosome, thus preventing the expression of otherwise fatal proteins.
"Some diseases develop because of a disturbance in the fine-tuning of protein dosages," Hentze says. "The control of protein synthesis is also crucial in the growth and development of animal tissues. Until a few years ago, scientists thought this happened almost uniquely at the level of genes. So its exciting to find an entirely new mechanism that evolved to let cells take control at the level of RNA. No one knows how widely this type of back-up mechanism is used. Were now investigating some other contexts in which a very similar mechanism might be at work."
Sarah Sherwood | EurekAlert!
The most recent press releases about innovation >>>
Die letzten 5 Focus-News des innovations-reports im Überblick:
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
New technique promises tunable laser devices
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...