The Role of a Scaffold Attachment Factor in Nuclear Assembly and Architecture

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The ongoing project is focussed on the role of the SAR-Specific DNA binding protein SAF-A (Scaffold Attachment Factor A) in the assembly of nuclei in extracts from Xenopus laevis eggs. In these extracts, nuclei form spontaneously around added DNA or chromatin. In the first period of the grant, we used microscopical and biochemical methods to investigate the fate of SAF-A during nuclear assembly. We could show that the protein associates with the insoluble nuclear scaffold in in vitro-assembled nuclei. Subsequent experiments will now investigate the role of the specific DNA binding for the localization ot the protein, and will show if the protein is necessary for the assembly or maintenance of a nuclear scaffold. In this context, we will also map the protein domain responsible for interaction of SAF-A with other protein components of the nuclear scaffold and for the self-assembly of SAF-A multimers. An additional project analyzes the role of SAF-A for the structure of chromosome territories assembled in vitro around human mitotic chromosomes. We expect that these experiments will provide a detailed insight into the role of a SAR binding protein for the architecture of the nucleus.