ITSSN · Investigation into the transduction of stress signals to the nucleus

Investigation into the transduction of stress signals to the nucleus

Project final report: grant agreement number 219452 Dr B. Westman & Prof AI Lamond WT Centre for Gene Regulation & Expression, College of Life Sciences, University of Dundee Dundee DD1 5EH, Scotland, UK Project website and contact details: http://www.lamondlab.com/f7bwestman.htm Introduction Cells are the fundamental building blocks of all living organisms, including humans. Our bodies are made up of around 1014 cells, of which there are many different types that have particular characteristics that enable them to carry out a particular function. For example, red blood cells have the ability to transport oxygen molecules, whereas liver cells are capable of metabolising drugs and synthesising cholesterol. However, although these mature cell types display an enormous number of different features, they are all derived from a similar precursor cell, known as a stem cell, in a process called differentiation. More surprisingly, nearly all cells within a particular individual contain exactly the same ensemble of DNA sequences. Genes encoded within these DNA sequences are activated or deactivated during cellular differentiation in a controlled and regulated manner, and this results in cells receiving different subsets of genetic information that direct and enable them to perform specific functions. Despite the many differences between fully differentiated cells in our bodies, there are also many similarities, in particular in the processes that determine the genetic information that is 'read' within a particular cell type. This information is contained within DNA, which is located within a specific region of the cell known as the 'nucleus'. This region can be visualised under a microscope by using fluorescent stains that specifically interact with DNA. Other stains (antibody- based) can be used to reveal internal nuclear regions such as 'nucleoli' and 'Cajal bodies' that contain specific protein and DNA molecules, demonstrating that the nucleus is highly organised. There are also similarities in the processes that determine how cells respond to changes in their environment, such as stress, in order to either adapt and therefore survive the change, or die to minimise the level of unhealthy cells within an organism. Many of the cellular stress responses involve changes within the cell nucleus and ultimately result in changes to which genes are activated or not. These changes are mediated by protein molecules that have received signals to change either their structure, location within the cell or interactions with other molecules. Since these stress response pathways are fundamental processes that operate in a large variety of cell types, it is important to understand these at a highly detailed, molecular level. Aim The aim of this project was to understand changes that occur within the cell nucleus and subnuclear regions such as nucleoli in both normal growth conditions and in response to stress. One change that is known to mediate stress responses is the attachment (Figure 1: The cell nucleus can be visualised under the microscope using specific stains for DNA (left)). The same nucleus can be co-stained to reveal subnuclear structures such as nucleoli (No) and Cajal bodies (CB). Scale bar = 10 microns posttranslational modification) of particular protein molecules to another class of protein molecules collectively referred to as 'SUMOs' (small ubiquitin-like modifiers). Therefore, we initially carried out a screen using the latest proteomic technology based on SILAC and mass spectrometry to identify proteins in nucleoli that can be modified by SUMO. The rest of the project aimed to confirm the results of this screen and to obtain molecular insight about the role of SUMOylation for the identified target proteins. Results and conclusions Our screen identified the proteins Nop58, dyskerin, Nhp2 and Nopp140 as major candidates for modification by SUMO in the nucleolus.

Data: CORDIS, © European Union