Structure defined of CCR4-NOT, a protein complex involved in the control of gene expression

CCR4-NOT is a complex of eight proteins that are very important in processes essential for life, such as the expression of gene information. Defects in the subunits of the complex can be lethal, or can be linked to heart problems or cancer.

The three-dimensional atomic structure was known for various parts of this complex, but others remained a mystery. Now, in collaboration with two Polish research centres, researchers at the CNB-CSIC have found the missing pieces. And, as if it were a puzzle, they have joined all the parts to obtain the complete CCR4-NOT structure in three dimensions. The results of this research were published today in the journal Nature Communications.

"Knowing the molecular structure of CCR4-NOT is very important for understanding how it controls processes so important to life as the processing of messenger RNA in the cell," says José María Valpuesta, researcher at the CNB-CSIC and lead author of the study.

A joint effort

Valpuesta explains that, despite international efforts, it had so far been impossible to obtain crystals of this protein complex (an important step in determining the atomic structure of any biological molecule). "That is why, until now, we were unable to determine the structure of the complex at high resolution,” explains the researcher. “In addition, it is a very difficult protein to purify, which greatly complicated the process."

To overcome these difficulties, the scientists opted for alternative techniques such as cryo-electron microscopy and different types of labelling. Thanks to these methods, complemented by atomic modeling, they were able to determine the structure of the protein complex at a resolution of 20 Å.

This study required the collaboration of various researchers from three different institutions, including the CNB-CSIC. The complex was purified in the Polish institutes and the Spanish centre determined the molecular architecture of the missing parts and pieced the puzzle together to obtain the complete structure of CCR4-NOT.

Marta Ukleja, Jorge Cuellar, Aleksandra Siwaszek, Joanna M. Kasprzak, Mariusz Czarnocki-Cieciura, Janusz Bujnicki, Andrzej Dziembowski and Jose Maria Valpuesta (2016) "The architecture of the Schizosaccharomyces pombe CCR4-NOT complex” Nature Communications DOI: 10.1038/NCOMMS10433

Image: (a) Distinct views of the pseudoatomic model generated using cryo-electron microscopy and atomic modelling. (b) Several views showing the location of the CCR4-NOT complex subunits. J. M. Valpuesta's lab, CNB-CSIC