The nucleolus is the largest functional domain in the nucleus of all human cells. Its primary role is the biogenesis of ribosomes, the complex machines that translate the language of nucleic acids (DNA and RNA) in to proteins. Nucleoli form around arrays of genes that encode the major RNA component of ribosomes. These ribosomal gene (rDNA) arrays, known as nucleolar organizer regions (NORs), are located on the short-arms of five human chromosomes.
Upstream Binding Factor (UBF) is a nucleolar specific HMG-box containing DNA binding protein that binds extensively across rDNA arrays. By constructing synthetic rDNA arrays comprised of high affinity UBF binding sites interspersed with gene promoters and ribosomal RNA coding sequences we have been able to construct functional neoNucleoli. This synthetic biology approach established the sequence requirements for nucleolar biogenesis and provides proof that this is a staged process, where UBF-dependent mitotic bookmarking precedes function-dependent nucleolar assembly.
Contrary to popular belief the human genome sequence is incomplete and missing regions include the NOR bearing short arms of human chromosomes 13, 14, 15, 21 and 22. We aim to describe the genomic architecture surrounding human NORs. This will involve de novo DNA sequence determination and identification of features that regulate the function and genomic stability of NORs. This research program will provide a description of how the chromosomal context of NORs influences nucleolar biology. It will also contribute to completion of the human genome and to a description of how it is organized in three dimensions within the human nucleus and how this changes through various biological processes.
Finally, our work will also provide new tools for nucleolar research and exploring its role in human disease. This work is supported by an investigator award 1(06199/Z/14/Z) from the SFI-HRB-Wellcome Trust Biomedical Research Partnership.