Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.31.1 (micrococcal nuclease)
 2,818 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Regions of An.Tn, (GA)n.(TC)n, and (GT)n.(AC)n have been cloned into the SmaI (CCC/GGG) site of plasmid pUC19. HindIII-EcoRI restriction fragments containing these inserts have been used as substrates for footprinting experiments using DNase I, DNase II, and micrococcal nuclease as probes. These present good mithramycin binding sites (GGG) flanking repetitive regions to which the drug does not bind. In each case, mithramycin footprints are observed at the CCC/GGG sites, which are not affected by the nature of the surrounding sequences. Some weaker binding is detected at TCGA and ACCA sites and at regions of alternating GA. No binding is found to regions of alternating GT. An.Tn inserts (n = 23 or 69) are normally resistant to cleavage by all these probes; in the presence of mithramycin, a dramatic increase in DNase I cleavage is observed throughout the entire insert and is indicative of an alteration in DNA structure. Similar changes are seen with DNase II and micrococcal nuclease. These changes cannot be explained by invoking changes in the ratio of free substrate to cleavage agent. In contrast, cleavage of (GA)n.(CT)n and (GT)n.(AC)n inserts is not affected by drug binding. The results are consistent with a model in which mithramycin causes dramatic changes in the width of the DNA minor groove, generating a structure which has some properties of A-DNA, and suggest that this can be propagated into surrounding DNA regions in a sequence-dependent manner. The structural alterations with An.Tn are highly cooperative and can be transmitted over at least three turns of the DNA helix.
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PMID:Effects of the antitumor antibiotic mithramycin on the structure of repetitive DNA regions adjacent to its GC-rich binding site. 182 82

An RNA-dependent RNA polymerase (RdRp) activity was detergent-solubilized from the chloroplast membranes of Chinese cabbage leaves infected with turnip yellow mosaic virus (TYMV). The template-dependent, micrococcal nuclease-treated activity synthesized full-length minus strands from TYMV RNA and 3'-fragments as short as a 28-nucleotide-long RNA comprising the amino acid acceptor stem of the 3'-tRNA-like structure (TLS). Minus strands were shown to arise by de novo initiation with the insertion of GTP opposite the penultimate (C) residue of the 3'-terminal -CCA. The TYMV RdRp activity was template specific in that poly(A) RNA was not copied, and alfalfa mosaic virus (AIMV) RNA, which does not contain a 3'-TLS, was a very poor template. However, other viral RNAs with a 3'-TLS and in vitro transcripts of tRNAs were copied to varying degrees. Fully modified tRNAs were either inactive or poorly active templates, and AIMV 3'-RNA, even when provided with a 3'-terminal -ACCA, was not copied detectably. A potential role of the acceptor stem pseudoknot as a promoter element was assessed with mutations that drastically altered the structure and sequence of the pseudoknot, revealing only a twofold effect in decreasing template activity. The data show that RNAs with both a tRNA-like conformation and a -CCA 3'-terminus are potential templates for TYMV RdRp and suggest that promoter elements are not limited to the acceptor stem pseudoknot.
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PMID:Turnip yellow mosaic virus RNA-dependent RNA polymerase: initiation of minus strand synthesis in vitro. 921 66