Engineered histones as DNA carriers with application in therapeutic gene delivery

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We intend to apply our knowledge of protein transport to the nucleus to enhance the delivery of DNA to target cells. This relates to the use of gene therapy to treat genetic defects such as inborn errors of metabolism, where a disease-causing lack-of-function mutation can be overcome by engineering cells within the organism which express, in the necessary quantities and in response to the appropriate regulatory signals, the particular component which is lacking. A limiting factor in gene therapy approaches is the low efficiency of nuclear uptake of introduced DNA, where it has been estimated that < 1% of the DNA taken up is actually expressed. Our proposal seeks to develop approaches to enhance non-viral-mediated gene delivery, in particular by optimising this critical, limiting step of the delivery of exogenous DNA to the nucleus. We intend to apply knowledge from studies of nuclear targeting and chromatin assembly to improve gene transfer technologies. We will build on our work showing that specific signals for nuclear import - nuclear targeting signals (NTSs) - can be used to enhance nuclear gene delivery and expression. Since DNA in the normal cellular context is in the form of chromatin - a specific complex with proteins such as histones - we intend to use reconstituted chromatin as the transfecting DNA, whereby histones engineered to include NTSs and other modular sequence elements will be used. Chromatin should not only enable NTSs and other sequence modules to be linked to the DNA but also protect against nuclease-mediated degradation prior to nuclear entry, condense the DNA to enable more efficient cellular-nuclear entry, and ensure expression of the transfected reporter gene by presenting it to the cell in a physiological context. Our approaches should contribute to bringing gene therapy closer to reality in the clinic.