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

Transcription of mouse mammary tumor virus DNA is stimulated by steroid hormones. The DNA sequences involved in this regulation are located in the viral long terminal repeat between positions -200 and -50 with respect to the transcription initiation site. In this region four, one distal and three proximal, in vitro binding sites for the glucocorticoid hormone-receptor complexes have been identified. We have prepared a series of 5' and 3' deletions of this region, using the exonuclease ExoIII. Combination of suitable 5' and 3' fragments enabled us to reconstitute the entire long terminal repeat with small internal deletions. The mutated long terminal repeats linked to the coding region of the Herpes simplex virus thymidine kinase gene were introduced into LTK- aprt- cells by transfection. Transcription from the mouse mammary tumor virus promoter in the presence or absence of hormone was assayed by nuclease S1 mapping. Deletion of the proximal in vitro binding sites resulted in a decrease in hormonal inducibility. When a synthetic oligonucleotide harboring the sequence of the distal in vitro binding site was inserted at the site of the proximal ones, hormone response was restored. This indicated that the distal binding site can replace the proximal ones in their hormone-regulatory function. However, insertion at the same site of an oligonucleotide containing the sequence 5' TGTTCT 3' found in all four binding sites, did not restore the hormone response, indicating that sequences flanking the TGTTCT motif are required for hormone response. Insertion of an unrelated DNA fragment at the site of the proximal binding element deletion completely abolished the hormone response. Analyses of different proximal binding-site deletion and insertion mutants suggested the presence of a transcriptional element located downstream from the most proximal hormone-receptor binding site.
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PMID:Functional analysis of the glucocorticoid regulatory elements present in the mouse mammary tumor virus long terminal repeat. A synthetic distal binding site can replace the proximal binding domain. 302 40

The 5' end of the Chinese hamster ovary aprt gene was sequenced and transcription start sites were determined by both S1 nuclease protection and primer extension assays. Deletion mutants covering the same area were constructed, and adenine phosphoribosyltransferase (APRT) or chloramphenicol acetyltransferase (CAT) activity was measured by transient-expression assays. The aprt gene uses a single cluster of transcription start sites and lacks consensus sequences such as TATA and CCAAT, which are general components of eucaryotic promoters. The 5' deletion mutations of the promoter sequences demonstrated that (i) there is no decrease in either APRT activity or transcription extending to position -89 (relative to the main transcription start site); (ii) an additional 29-base-pair (bp) deletion decreases APRT activity and transcription twofold; and (iii) a deletion past the transcription start sites (P5' delta +27) abolishes both APRT activity and transcription, indicating that a 60-bp fragment immediately upstream of the main transcription start site is involved in basic transcription and a 29-bp fragment just upstream of the 60 bp-fragment stimulates transcription twofold. The 3' deletion mutations showed that a deletion of a 61-bp fragment in the 5' leader and coding sequence abolishes the efficient translation of an aprt-CAT gene transcript. In addition, there are two polyadenylation signals at the genomic 3' end, with the proximal one being sufficient for functional polyadenylation.
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PMID:Analysis of signals controlling expression of the Chinese hamster ovary aprt gene. 340 12

Transcription of mouse mammary tumor virus (MMTV) DNA is stimulated by steroid hormones. To determine the DNA sequences involved in this regulation, we constructed a plasmid containing the MMTV long terminal repeat (LTR) in front of the coding region of the herpes simplex thymidine kinase gene, from which the promoter had been removed. Portions of the LTR were removed by the nuclease Ba/31, and the deleted molecules were recloned and tested for transcriptional activity in transfections of Ltk-aprt- cells. Stably transfected cell clones were selected and hormone-dependent transcription from the MMTV promoter was studied by the S1 nuclease mapping method. The results show that DNA sequences between -105 and -204 base pairs upstream from the initiation site of viral transcription are required for glucocorticoid stimulation.
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PMID:Glucocorticoid regulation of mouse mammary tumor virus: identification of a short essential DNA region. 1087 40