Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.4.2.8 (hypoxanthine-guanine phosphoribosyltransferase)
 2,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The engineering of therapeutic human artificial episomal chromosomes, HAECs, requires the development of strategies to deliver large functional self-replicating extrachromosomal DNA in target cells. Members of the herpesviral family are among the largest episomal double-stranded DNA viruses. As model systems of this family of endemic infectious agents, vectors derived from the human herpes 4 Epstein-Barr virus (EBV) were constructed which transferred up to 180 kb of DNA packaged as infectious virions. Such a transduction strategy was based on a non-oncogenic helper-dependent mini-EBV carrying minimal cis elements for latent replication and virus production. After exposure of human B lymphoma and lymphoblastoid cells to mini-EBVs transducing lacZ and human HPRT minigenes, stable cell transformants were selected which carried the delivered multimeric linear DNAs as circular episomes up to 160-180 kb in size. Following transduction of Lesch-Nyhan disease cells with a mini-EBV/HPRT, normal human HPRT function was restored in cells carrying large episomal HPRT minigenes. Direct visualization of the therapeutic mini-EBV by fluorescent in situ hybridization (FISH) on metaphase and interphase nuclei indicated that 99% (556/563) of the transduced mini-EBV DNA was episomal with an average copy number of one to two per nucleus. This system should allow the delivery of large genes in common diseases such as hemophilia A and codelivery of multiple genes in cells from polygenic diseases such as cancer. The extrachromosomal mini-EBV-based strategy offers an alternative to integrative or non-replicating gene therapy infectious vectors, which may be generally applicable to other herpesviruses characterized by different tropisms.
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PMID:Engineering a mini-herpesvirus as a general strategy to transduce up to 180 kb of functional self-replicating human mini-chromosomes. 898 34

Persistent expression of a transgene at therapeutic levels is required for successful gene therapy, but many small vectors with heterologous promoters are prone to vector loss and transcriptional silencing. The delivery of genomic DNA would enable genes to be transferred as complete loci, including regulatory sequences, introns, and native promoter elements. These elements may be critical to ensure prolonged, regulated, and tissue-specific transgene expression. Many studies point to considerable advantages to be gained by using complete genomic loci in gene expression. Large-insert vectors incorporating elements of the bacterial artificial chromosome (BAC) cloning system, and the episomal maintenance mechanisms of Epstein-Barr virus (EBV), can shuttle between bacteria and mammalian cells, allowing large genomic loci to be manipulated conveniently. We now demonstrate the potential utility of such vectors by stably correcting a human genetic deficiency in vitro. When the complete hypoxanthine phosphoribosyltransferase (HPRT) locus of 115 kilobases (kb) was introduced into deficient human cells, the transgene was both maintained as an episome and expressed stably for six months in rapidly dividing cell cultures. The results demonstrate for the first time that gene expression from an episomal genomic transgene can correct a cell culture disease phenotype for a prolonged period.
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PMID:Stable correction of a genetic deficiency in human cells by an episome carrying a 115 kb genomic transgene. 1110 14


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