Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

High-level expression of a transpositionally competent Ty1 element fused to the inducible GAL1 promoter on a 2 microns plasmid (pGTy1) overcomes transpositional dormancy in Saccharomyces cerevisiae. To investigate the mechanisms controlling the rate of Ty1 retrotransposition, we quantitated transposition and Ty1 gene products in cells induced and uninduced for expression of pGTy1. The increase in Ty1 transposition was 45- to 125-fold greater than the increase in Ty1 RNA effected by pGTy1 induction. Translational efficiency of Ty1 RNA was not altered in transposition-induced cells, since p190TYA1-TYB1 protein synthesis increased in proportion to steady-state Ty1 RNA levels. Therefore, expression of a pGTy1 element increases the efficiency of Ty1 transposition at a posttranslational level. Galactose induction of pGTy1 enhanced TYA1 protein processing and allowed detection of processed TYB1 proteins, which are normally present at very low levels in uninduced cells. When the ability of genomic Ty1 elements to complement defined mutations in HIS3-marked pGTy1 elements was examined, mutations in the protease domain or certain mutations in the integrase domain failed to be complemented, but mutations in the reverse transcriptase domain were partially complemented by genomic Ty1 elements. Therefore, the activity of Ty1 elements in yeast cells may be limited by the availability of Ty1 protease and possibly integrase. These results suggest that Ty1 transposition is regulated at the level of protein processing and that this regulation is overcome by expression of a pGTy1 element.
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PMID:Posttranslational control of Ty1 retrotransposition occurs at the level of protein processing. 131 8

The production of gene therapy retroviral vectors presents many difficulties, mainly due to vector instability and low cell productivities hampering the attainment of high titers of infectious viral vectors. The objective of this work is to increase the production titers of retroviral vectors by manipulating the sugar carbon sources used in bioreaction. Four sugars were tested (glucose, galactose, sorbitol, and fructose) on an established Moloney murine leukemia virus (MoMLV) producer cell line. Galactose and sorbitol did not support cell growth or vector production. Glucose supplemented at 25 mM supported the highest cell growth; however, the use of glucose or fructose at 83 and 140 mM have shown to improve the infectious vector titer three to fourfold. The reasons for the titer improvements were further analyzed and, although, the cell-specific productivity in viral transgene RNA and reverse transcriptase were augmented 5- and 6-fold for glucose at 140 mM and 14- and 16-fold for fructose at 140 mM, comparing with glucose at 25 mM, these increases did not seem sufficient to account for the 14- (140 mM glucose) and 32- (140 mM fructose) fold increment obtained for the infectious particles-specific productivity. Further accounting the enhancement in the titers was the improvement in the viral stability, the half-life of the vectors was enhanced by 30-60%. This resulted in a product quality with a superior ratio of infectious to total particles, thus reducing the most problematic contaminant in the production of retroviral vectors, non-infectious retroviral particles.
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PMID:Effect of medium sugar source on the production of retroviral vectors for gene therapy. 1651 78