Expression of Genes Encoded for Functional Proteins

The development of cell and gene therapy was driven by the desire to treat the disease rather than the symptoms. For genetic 

Two clinical applications have validated the field of gene therapy. The first involves ex vivo transfer of a gene that encodes for 

This section will describe the features and clinical applications for each gene delivery system. The description will start with a common feature of both viral and nonviral gene delivery systems, the expression cassette for the therapeutic protein. 

Most cellular genes are composed of intron and exon sequences. During maturation of the RNA transcript, the introns are excised and the exons are ligated together. This processing step also facilitates export of RNA from the nucleus into the cytoplasm for protein translation. At least one intron and one exon are almost always included in the therapeutic expression cassette to ensure that the engineered transcript is processed in the same manner as the natural cellular transcript. 

The intron/exon, 5 UTR, 3 UTR, and the poly-A tail all affect gene expression by modulating the turnover and intracellular trafficking of the transcript. The promoter, usually accompanied by an enhancer element, controls the number of transcripts that are synthesized. The enhancer, acting through the promoter, can dramatically increase gene expression. 

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DELIVERY AND EXPRESSION OF GENES ENCODED FOR FUNCTIONAL PROTEINS... 

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