Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Findings in frog oocytes may help study of chromosome physiology

15.08.2003


After immunofluorescent staining with two antibodies, the protein XCAP-D2 is evident in red on the lampbrush chromosomes (green) in the nucleus of a frog oocyte. The red signal is associated with highly condensed but transcriptionally inactive regions, while the green indicates long loops of intense transcription.
Photo courtesy of Michel Bellini


Researchers studying the nuclei of frog oocytes in early stages of meiosis -- the cell division that gives rise to germ cells -- have found that two key proteins remain apart at a crucial time before condensation occurs. One of the proteins, they say, may be important in the early organization of chromosomes and later may recruit the other.

In the August issue of the journal Chromosome Research, scientists at the University of Illinois at Urbana-Champaign detail how they used antibodies to the proteins, XCAP-E and XCAP-D2, and confocal laser scanning microscopy to zero in on the proteins’ precise locations inside the nuclei of gametes of the African frog Xenopus laevis.

(The research will be on display as a poster presentation Aug. 17-22 during the Gorden Research Conference on Plasmid & Chromosome Dynamics in Tilton, N.J.)



The proteins are from two subcomplexes of chromosome condensation proteins known as condensins. One group of the Xenopus Chromosome Associated Proteins (XCAP), including XCAP-D2, consists of regulatory proteins, while XCAP-E is among those directly involved in condensation.

"On the chromosomes, XCAP-D2 was only found associated with the chromomeres," said Michel Bellini, a professor of cell and structural biology at Illinois. That location features highly compacted chromatin, or fibers of DNA, suggesting XCAP-D2 is directly involved early in meiotic chromatin organization.

Immunofluorescent staining showed XCAP-D2 proteins on the 18 easily recognizable chromosomes of the frog oocyte. These extended chromosomes stretch out long loops of chromatin -- regions of extensive RNA synthesis -- causing them to resemble a lampbrush, and, more importantly, allowing for detailed cytological studies of the major components implicated in both RNA transcription and chromatin organization.

"When we looked for XCAP-E, we did not see it on the chromosomes," Bellini said. "Instead, it was accumulated in the nucleoli, small organelles containing ribosomal DNA."

"This discovery came as a big surprise for us," he said. "When you deal with chromosomal proteins, you expect them to be found on the chromosomes." Because the two proteins were segregated, he added, there was no overlapping of signals.

The proteins have equivalents in other organisms, so the findings may help other studies of chromosome physiology, especially the functional aspects of these proteins, Bellini said. At the critical time of cell division, chromosome packaging is vital. Genetic errors can result in deformities, diseases such as cancer and/or the death of the organism.

Frog oocytes are large, allowing researchers to easily manipulate genetic material. A nucleus, for example, is 400 microns in diameter. A human red blood cell is 8-10 microns.

Bellini’s doctoral student Brent Beenders did much of the research, which was funded by the National Institutes of Health and the Cancer Research Association of France.

"What we propose is that in the oocytes XCAP-E may not be required in the very early stages of meiosis," Bellini said. "XCAP-E is there. The fact that it is in the nucleolus may be simply to prevent its association with XCAP-D2 at this stage. Perhaps at this stage condensation is not wanted but active transcription is necessary. This might be one way to prevent condensation. The nucleolus is acting as a trap for this nuclear protein’s action. It may be that XCAP-D2 calls in XCAP-E when condensation is needed."

Bellini’s team also found both proteins in the Cajal bodies -- small independently floating organelles -- that are theorized to be important in the assembly and modification of the RNA transcription and processing machinery. "This finding suggests the exciting possibility that Cajal bodies might also be implicated in the assembly of chromatin remodeling complexes," Bellini said.

Understanding how condensation proteins operate at the cellular level will help scientists work to understand their molecular role in chromatin condensation, he added.

Other contributors to the study were Erwan Watrin and Vincent Leganeux, both of the National Center for Scientific Research in France, and Igor Kireev of the department of cell and structural biology at Illinois and Moscow State University in Russia.

Jim Barlow | UIUC
Further information:
http://www.uiuc.edu/
http://www.news.uiuc.edu/scitips/03/0814bellini.html

More articles from Life Sciences:

nachricht More genes are active in high-performance maize
19.01.2018 | Rheinische Friedrich-Wilhelms-Universität Bonn

nachricht How plants see light
19.01.2018 | Albert-Ludwigs-Universität Freiburg im Breisgau

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Let the good tubes roll

19.01.2018 | Materials Sciences

How cancer metastasis happens: Researchers reveal a key mechanism

19.01.2018 | Health and Medicine

Meteoritic stardust unlocks timing of supernova dust formation

19.01.2018 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>