Modifying, and Transferring Genes

Manipulation of the genetic code through recombinant DNA allows molecular biologists to modify and transfer genes both for the study of disease and the production of new cellular characteristics. 

The ADA enzyme normally prevents the accumulation of toxic deoxy-ATP in cells. Deoxy-ATP is particularly toxic to lymphocytes, and leads to death of T and cells. Absence of the enzyme therefore results in SCID. Infusion of the purified enzyme (pegademase, from bovine sources) and transfer of ADA gene-modified lymphocytes have both been used successfully to treat this disease. 

R. Gonzalez, R. Vereecque, T. J. Wickham, M. Vanrumbeke, I. Kovesdi, F. Bau-ters, P. Fenaux, and B. Quesnel, Increased gene transfer in acute myeloid leukemic cells by an adenovirus vector containing a modified fiber protein, Gene Ther. 6 314 (1999). 

G. A. McDonald, G. Zhu, Y. Li, I. Kovesdi, T. J. Wickham, and V. P. Sukhatme, Efficient adenoviral gene transfer to kidney cortical vasculature utilizing a fiber modified vector, J. Gene Med. 7 103 (1999). 

Short, D. K, Okada, S., Yamauchi, K. and Pessin, J. E. (1998). Adenovirus-mediated transfer of a modified human proinsulin gene reverses hyperglycemia in diabetic mice. Am. J. Physiol. 275, E748-E756. 

All classes of RNA transcripts must be processed into mature species. The reactions include several types Nucleolytic cleavage, as in the separation of the mature rRNA species from the primary transcript of RNA polymerase I action Chain extension (non-template-directed), as in the synthesis or regeneration of the common CCA sequence at the 3 end of transfer RNAs or of PolyA at the 3 end of mRNAs and Nucleotide modification, for example, the synthesis of methylated nucleotides in tRNA or rRNA. These reactions are a feature of both prokaryotic and eukaryotic gene expression, and the biological consequences are diverse. For example, modified nucleotides can affect the way in which a tRNA recognizes different codons. 

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