Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

UT MD Anderson scientists uncover the nuclear life of actin

25.03.2013
Protein with key job in muscle function moonlights in nucleus to help regulate genes

A key building block of life, actin is one of the most abundant and highly conserved proteins in eukaryotic cells.

First discovered in muscle cells more than 70 years ago, actin has a well-established identity as a cytoplasmic protein that works by linking itself in chains to form filaments. Fibers formed by these actin polymers are crucial to muscle contraction.

So it came as a surprise when scientists discovered actin in the nucleus. Labs have been working for the past few decades to figure out exactly what it's doing there.

A new study published this week in Nature Structural & Molecular Biology reveals that actin has a new and fundamental nuclear function, and that surprisingly, it accomplishes this task in its single-molecule (monomeric) form – not through polymerization.

Senior author of the study Xuetong "Snow" Shen, Ph.D., associate professor in The University of Texas MD Anderson Cancer Center Department of Molecular Carcinogenesis, has been fascinated by the mystery of nuclear actin. In collaboration with researchers from Colorado State University, his lab developed a unique model system to nail down actin's function in the nucleus by studying the actin-containing INO80 chromatin remodeling complex.

In 2000, as a postdoc at NIH in Carl Wu's lab, Shen identified actin as a component of the INO80 complex, adding to the growing list of evidence that actin indeed has a life in the nucleus. However, how actin actually works in the nucleus remains fuzzy due to lack of clear experimental systems.

"Our model system opened up a new opportunity to look in depth at the function of nuclear actin as it relates to gene regulation, genome stability, and ultimately cancer," Snow said.

A nuclear role for monomeric actin

Because yeast have only a single actin gene, the authors reasoned that studying INO80 in yeast cells would allow a direct assessment of the protein's nuclear function. In contrast, mammals have at least six forms of actin coded by separate genes, making their study more difficult.

The researchers used both genetic and biochemical methods to dissect actin's role in the INO80 complex. The INO80 complex normally functions in the nucleus to rearrange chromatin ¬– the intertwined proteins and DNA that are packaged into chromosomes – regulating the expression of many different genes.

The authors found that a mutant form of actin impairs the ability of INO80 to function correctly, implicating actin in the process of chromatin remodeling – an exploding field of research with applications in cancer diagnosis and treatment.

In the cytoplasm, actin functions primarily as a polymer. Cytoplasmic actin is a component of the cytoskeleton and the muscle contractile machinery, and is essential for cell mobility, including cancer metastasis. Actin inside the INO80 complex is arranged in a clever way such that it cannot polymerize; instead, actin's monomeric form appears to interact with chromatin.

"Our study challenges the dogma that actin functions through polymerization, revealing a novel and likely a fundamental mechanism for monomeric nuclear actin," Shen said.

New findings for an ancient complex

Because actin and several of the other INO80 components are so highly conserved, even in human cells, this mechanism likely represents an ancient, fundamental role of actin, which has been preserved through evolution.

Shen's group is now teasing out the exact mechanism by which nuclear actin interacts with chromatin. They also hope to extend the results to human cells and to identify potential ways by which nuclear actin could be involved in cancer.

Chromatin is critical for maintaining the delicate balance between gene activation and repression, Shen said. "Disrupting this regulation can lead to cancer, and it remains to be seen whether nuclear actin has a role in this process."

Lead authors of the study are Prabodh Kapoor, Ph.D., and Mingming Chen, Ph.D., postdoctoral fellows in Shen's lab. Co-authors are Duane David Winkler, Ph.D., and Karolin Luger, Ph.D., of the Department of Biochemistry and Molecular Biology at Colorado State University. Shen, senior author, also is a member of the Center for Cancer Epigenetics at MD Anderson.

The research was funded by grants from the National Cancer Institute (K22CA100017) and the National Institute of General Medical Sciences (RO1GM093104), both of the National Institutes of Health, the Center for Cancer Epigenetics, the Theodore N. Law Endowment for Scientific Achievement at MD Anderson and by MD Anderson's Odyssey postdoctoral program to Kapoor

About MD Anderson

The University of Texas MD Anderson Cancer Center in Houston ranks as one of the world's most respected centers focused on cancer patient care, research, education and prevention. MD Anderson is one of only 40 comprehensive cancer centers designated by the National Cancer Institute. For eight of the past 10 years, including 2011, MD Anderson has ranked No. 1 in cancer care in "America's Best Hospitals," a survey published annually in U.S. News & World Report.

Get M. D. Anderson News Via RSS Follow MDAnderson News on Twitter

Scott Merville | EurekAlert!
Further information:
http://www.mdanderson.org

More articles from Life Sciences:

nachricht Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery
20.01.2017 | GSI Helmholtzzentrum für Schwerionenforschung GmbH

nachricht Seeking structure with metagenome sequences
20.01.2017 | DOE/Joint Genome Institute

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>