Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.1 (S1 nuclease)
 3,660 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mouse thymidylate synthase minigenes that lack introns were constructed by ligating restriction fragments containing 4.5, 1.0, or 0.25 kilobase pairs (kb) of 5'-flanking DNA of the normal thymidylate synthase gene and as little as 0.25 kb of 3'-flanking DNA to full-length thymidylate synthase cDNA. All three minigenes were expressed at approximately the same levels following transfection into hamster V79 cells that were deficient in thymidylate synthase. S1 nuclease protection assays revealed that the multiple 5' and 3' termini of thymidylate synthase mRNA in cells transfected with these minigenes were at the same positions as those of the normal mRNA in mouse cells. Deletion analysis of the promoter region revealed that minigenes extending to position -150 nucleotides (relative to the AUG codon) were expressed at approximately the same level as those extending to -1 kb. However, minigenes extending to -53 nucleotides were inactive. To determine if the minigenes were capable of being regulated in a cell cycle-dependent manner, thymidylate synthase gene expression was measured in hamster cells that were stably transfected with the largest minigene and synchronized by serum-stimulation. Thymidylate synthase enzyme level and mRNA content increased 3-5-fold as cells progressed from G1 through S phase.
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PMID:Construction and expression of mouse thymidylate synthase minigenes. 282 52

Thymidylate synthase (TS) mRNA content increases about 20-fold when growth-stimulated mouse cells progress from the G0/G1 phase into the S phase of the cell cycle. Previous studies, using a cell line in which the TS gene is amplified (LU3-7), indicated that transcriptional initiation as well as polyadenylation of the mRNA occur at several locations in unsynchronized cells. In the present study, we have used S1 nuclease protection assays to analyze the possible significance of the multiple transcriptional initiation and polyadenylation sites. We found that the same pattern of 5' and 3' termini were detected with RNA isolated from the overproducing cells as with RNA isolated from the parental mouse 3T6 cell line, demonstrating that the heterogeneous termini are not a consequence of gene amplification. There was no change in the pattern of 5' or 3' termini with either cell line during the progression from G1 phase through S phase in serum-stimulated cells. Therefore, the increase in TS mRNA content is not the result of differential utilization of the various transcriptional initiation or polyadenylation sites. Analyses of poly(A)- deficient cytoplasmic TS RNA showed that the 5' termini were the same as those found in poly(A) + mRNA. However, the 3' termini were extremely heterogeneous in length. Although some of the poly(A)- deficient RNA extended beyond the normal site of polyadenylation, most of it was shorter than full-length TS mRNA.
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PMID:Analysis of the multiple 5' and 3' termini of poly(A)+ and poly(A)-deficient thymidylate synthase mRNA in growth-stimulated mouse fibroblasts. 291 37

Thymidylate synthase (TS) is an essential enzyme that must be expressed in all proliferating cells. The mouse TS promoter lacks a TATA box and an initiator element and initiates transcription over a broad region in cultured fibroblasts. The goal of this study was to determine if expression of the TS gene in a variety of cells and tissues involves the use of alternative promoters or different patterns of transcriptional initiation sites. The amount of TS mRNA and the pattern of initiation sites were determined using S1 nuclease protection assays. We found that even though the amount of TS mRNA varied over a wide range, reflecting differences in cell proliferation rates, the pattern of initiation sites was nearly identical in all of the cell lines and tissues that were examined. Therefore transcription of the TS gene is directed by a single promoter that is capable of being expressed in a wide variety of cellular environments.
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PMID:Complex transcriptional initiation pattern of the thymidylate synthase promoter in mouse tissues. 1060 Jan 80