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)

A series of spontaneous and ethyl methanesulfonate-induced 6-thioguanine-resistant mutants were isolated in the CHO-10T5 cell line. This cell line was constructed by the introduction of a shuttle vector containing the Escherichia coli gpt gene into a hypoxanthine-guanine phosphoribosyltransferase deficient derivative of the Chinese hamster cell line CHO-K1. Shuttle vector sequences were recovered from many of the mutant cell lines by the COS cell fusion technique and the DNA base sequence of the gpt genes was determined whenever possible. The base sequences were determined for gpt genes recovered from 29 spontaneous mutants. Of these 29 mutants, 9 have single base substitutions, 1 has a small duplication, 17 have simple deletions, 1 has a deletion with additional bases inserted at the deletion site, and 1 has no change in the gpt coding sequence. Many of the deletions were less than 20 basepairs in length and several occurred in a region previously observed to be a hotspot for spontaneous deletions. The generation of the deletion/insertion mutation may have involved a quasi-palindromic intermediate. A total of 59 ethyl methansesulfonate-induced mutants were isolated and vector sequences were recovered from 50 mutants. All 50 mutants sequenced had single base substitutions and most (45) were G:C to A:T transitions. While there were no strong hotspots in this collection of mutations, the site distribution was obviously nonrandom. Many of the G:C to A:T transitions either produced a nonsense codon or occurred at glycine codons.
 ...
PMID:DNA base sequence changes in spontaneous and ethyl methanesulfonate-induced mutations of a chromosomally-integrated gene in Chinese hamster ovary cells. 138 28

The abundant production of antisense hypoxanthine phosphoribosyltransferase (HPRT) RNA in NIH-3T3, COS, or HeLa cells leads to an inhibition of HPRT synthesis. HPRT enzyme levels in cells transfected with mouse HPRT antisense RNA expression vectors are reduced to less than 1% of parental cell activity, resulting in resistance to 6-thioguanine (6TG). The expression of antisense HPRT RNA leads to a marked reduction in the steady-state levels of endogenous HPRT mRNA. Furthermore, we demonstrate that intron-specific antisense RNA, complementary to sequences adjacent to splice donor or acceptor sites of the first intron of the mouse HPRT gene, are effective in depressing endogenous HPRT levels. These studies suggest that antisense RNA can inhibit gene expression in the nucleus, possibly by perturbing nuclear RNA processing.
 ...
PMID:Antisense RNA inhibition of HPRT synthesis. 221 24

cDNA of the human hprt gene was introduced into the BamHI cloning site of the retroviral shuttle vector pZipNeoSV(X)1. The mouse cell line 2TGOR, a hypoxanthine phosphoribosyltransferase-deficient derivative of Balb/c 3T3, was transformed with the vector and some stably transformed HATrNEOr clones were established. One of the clones, VH-12, contained a single copy of the vector integrated stably into a chromosome in a proviral form. From this clone, we were able to recover efficiently the vector sequence preserving its intact structure by use of COS cell fusion. The relatively small size of the hprt cDNA (657 base pairs for the coding region) allowed quick determination of the entire DNA sequence. It was also notable that use of 6TG NEO double selection for mutant isolation could eliminate the 6TGr derivatives of VH-12 cells which arose from loss of the total vector sequence or from some epigenetic event, because such alterations would lead to inactivation of the neo gene as well as the hprt cDNA. The properties of our shuttle vector system were particularly useful for analysis of the molecular mechanisms of mutational events in chromosomal DNA of mammalian cells.
 ...
PMID:Shuttle vector system for the analysis of mutational events in mammalian chromosomal DNA. 291 Dec 54

The simian virus 40 (SV40)-pBR322 recombinant, pSV2, carrying the origin of SV40 replication and the gpt gene of Escherichia coli, has been stably introduced into Chinese hamster ovary hprt- cells. All gpt-transformed cell lines were found to contain one or more insertions of pSV2 sequences exclusively associated with high-molecular-weight DNA. Additional analyses showed that at least one integrated copy in each cell line retained an intact gpt gene and flanking SV40 sequences required for expression of xanthine-guanine phosphoribosyltransferase. Most cell lines contained pSV2 sequences which had integrated with partial sequence duplication. Upon fusion with COS-1 cells, a simian cell line permissive for autonomous pSV2 replication, most gpt-transformed cell lines produced low-molecular-weight DNA molecules related to pSV2. The majority of these replicating DNAs were indistinguishable from the original transfecting plasmid in both size and restriction enzyme cleavage pattern. In addition, the recovered DNA molecules were able to confer ampicillin resistance to E. coli and to transform mouse L cells and Gpt- E. coli to a Gpt+ phenotype. These studies indicate that all of the genetic information carried by this SV40-plasmid recombinant can be introduced into and retrieved from the genome of mammalian cells.
 ...
PMID:Introduction and recovery of a selectable bacterial gene from the genome of mammalian cells. 629 Aug 75