Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.5.1.2 (DNA ligase)
 2,749 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Availability of 4-thiouridine (4-thioU)-containing RNAs is the prerequisite for 4-thioU site-specific cross-linking studies. This paper presents a method for constructing such RNAs. A 5'- and a 3'-RNA are synthesized via phage RNA polymerase transcription and/or RNase H site-specific cleavage directed by 2'-O-methyl-RNA-DNA chimeras. These two half-RNAs in combination correspond to the sequence of full-length RNA, with a single nucleotide gap at the junction that will be filled in with a 4-thiouridylate. A single p4SUp, which is derived from 4SUpN (N can be any nucleotide) via 5'-phosphorylation (therefore, the phosphate can be radioactive) followed by RNase A digestion, is then ligated to the 3' end of the 5'-half RNA with T4 RNA ligase. The 3'-phosphate of the ligated product is subsequently removed by calf intestinal alkaline phosphatase to produce a 3'-hydroxyl group. The resulting 5'-half RNA and the 3'-half RNA with a 5'-phosphate group (which can also be radioactive) are then aligned with a bridging deoxyoligonucleotide and ligated with T4 DNA ligase. This method was previously applied to the P120 pre-mRNA that contains an AT-AC intron, yielding three RNAs each containing a single 4-thioU near the 5'-splice site. Subsequent cross-linking studies with these RNAs yielded detailed information regarding interactions between the 5'-splice site and other spliceosomal snRNAs and between the 5'-splice site and proteins during splicing. Because there is no sequence constraint surrounding the site of 4-thioU substitution, this method should be applicable to many other RNAs.
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PMID:Construction of 4-thiouridine site-specifically substituted RNAs for cross-linking studies. 1020 12

A novel inhibitor of topoisomerases designated as topostatin was isolated from the culture filtrate of Thermomonospora alba strain No. 1520. The inhibitory activity of topostatin was shown to be pH- and temperature-dependent with a maximum around at pH 6 and 28 degrees C. The stability of topostatin decreased with decreasing pH and rising temperature. Topostatin inhibited topoisomerases I and II in a competitive manner with respect to DNA. The inhibitor also inhibited some restriction endonucleases such as Sca I, Hind III and Pst I, but not Alu I, Bam HI, Eco RI, RNase A, DNase I, DNase II and DNA ligase. Topostatin did not induce the nuclear accumulation of p53 protein by DNA damage in the normal human cells.
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PMID:Topostatin, a novel inhibitor of topoisomerases I and II produced by Thermomonospora alba strain No. 1520. III. Inhibitory properties. 1048 May 69