HOUSTON -- 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 nuc
|Contact: Scott Merville|
University of Texas M. D. Anderson Cancer Center