Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Defective avian leukosis virus (ALV)-based vectors expressing the neo and LacZ genes were constructed under the control of cis-acting elements originated from 4 avian retroviruses: avian erythroblastosis virus (AEV), Rous associated viruses 1 (RAV-1) and 2 (RAV-2), and the Schmidt Ruppin strain of Rous sarcoma virus subgroup D (SR-RSV-D). We used these vectors to study the long-term stability of beta-galactosidase expression (encoded by the LacZ gene) in a permanent cell line from quail fibroblasts (QT6). Infection of the immortalized QT6 cell line with these vectors resulted in unstable beta-galactosidase expression. We determined whether this instability of provirus expression was correlated with: (1) presence of G418 selection; (2) deletion in the proviral genome; (3) hypermethylation of the proviral genome; (4) position of the neo and LacZ genes in the proviral genome; and (5) the transcriptional activity of the long terminal repeat (LTR) elements of proviral vectors. We observed that G418 selection pressure applied to infected QT6 cells lead to a more stable LacZ gene expression. Moreover, our results suggest a correlation between the stability of proviral gene expression and the level of gene expression driven by the LTR elements and depending on the strain origin of these.
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PMID:Influence of expression and cis-acting sequences from avian leukosis viruses (ALVs) on stability of (ALV)-based retrovirus vectors. 767 Oct

We previously showed that the yeast three-hybrid system provides a genetic assay of both RNA and protein components for avian retroviral RNA encapsidation. In the current study, we used this assay to precisely define cis-acting determinants involved in avian leukosis sarcoma virus packaging RNA binding to Gag protein. In vivo screening of Rous sarcoma virus mutants was performed with randomly mutated minimal packaging sequences (MPsi) made using PCR amplification after cotransformation with GagDeltaPR protein into yeast cells. Colonies with low beta-galactosidase activity were analyzed to locate mutations in MPsi sequences affecting binding to Gag proteins. This genetic assay delineated secondary structural elements that are important for efficient RNA binding, including a single-stranded small bulge containing the initiation codon for uORF3, as well as adjacent stem structures. This implies a possible tertiary structure favoring the high-affinity binding sites for Gag. In most cases, results from the three-hybrid assay were well correlated with those from the viral RNA packaging assays. The results from random mutagenesis using the rapid three-hybrid binding assay are consistent with those from site-directed mutagenesis using in vivo packaging assays.
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PMID:Yeast three-hybrid screening of rous sarcoma virus mutants with randomly mutagenized minimal packaging signals reveals regions important for gag interactions. 1098 63

This study describes an in utero approach for overexpressing genes in a cell-type directed manner. It uses an avian leukosis retroviral expression system coupled with a transgenic mouse line expressing the viral receptor tv-a from a tissue-specific promoter (RCAS-TVA system) (Federspiel et al., 1994, and reviewed in Fisher et al., 1999). A transgenic mouse line was generated expressing tv-a from the Dopachrome tautomerase promoter (DCT-tv-a) in embryonic melanocyte precursors (melanoblasts). RCAS virus encoding beta-galactosidase (RCAS-LacZ) or tyrosinase (RCAS-Tyr) was injected in utero into embryonic day 12.5 albino (tyrosinase inactive) mouse embryos. Animals were analyzed for beta-galactosidase activity or tyrosinase activity (hair pigmentation). RCAS gene expression was detected in 44% and 25% of the transgenic mice, respectively. We demonstrate the RCAS-TVA system coupled with the DCT-tv-a line of mice can be used for in utero infection.
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PMID:In utero complementation of a neural crest-derived melanocyte defect using cell directed gene transfer. 1141 66