Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.26.4 (RNase H)
 2,751 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

RNase H has been clearly implicated in vitro in mediating some antisense effects. In vivo evidence is limited to experiments performed in Xenopus oocytes in which antisense oligonucleotides are microinjected. In other mammalian cell systems scant data have been obtained to support or deny a role for RNase H as an antisense mediator in vivo. These experiments were designed to test the hypothesis that RNase H mediates the MYC antisense-induced reduction in MYC protein observed in the human monocytic leukemia cell line U937. A bacterial RNase H-containing episomal replicon was constructed and stable transfectants were obtained which expressed E coli RNase H in their cytoplasm at a 10-fold higher level than endogenous RNase H. These cells failed to demonstrate heightened sensitivity to MYC antisense (phosphorothioate, end capped and phosphodiester) compared with untransfected or E coli RNase H antisense transfected cells. PCR analysis of each transfectant treated and untreated with MYC antisense failed to demonstrate the appearance of truncated MYC mRNA. These results do not support a role for RNase H in the mediation of MYC antisense-induced MYC protein reduction and growth inhibition in U937 cells.
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PMID:Effect of over-expression of bacterial ribonuclease H on the utility of antisense MYC oligodeoxynucleotides in the monocytic leukemia cell line U937. 838 12

A 28-mer morpholino oligonucleotide analog was designed to hybridize to 8 bases of intron 1 and extend 2 bases beyond the translation initiation codon in exon 2 of the unspliced c-myc RNA transcript. Delivery of this compound into human chronic myeloid leukemia KYO1 cells, by streptolysin O permeabilization, resulted in almost total ablation of the 65 kDa c-MYC protein expression for at least 24 hours after treatment. An unexpected band with SDS-PAGE electrophoretic mobility indicating a protein of about 47 kDa was apparent on the 24-hour western blots that were developed using antibodies that recognize MYC protein C terminal epitopes. No inhibition of the approximately 2400 nt c-myc mRNA expression was observed by northern hybridization, a result of the inability of morpholino analogs to direct the activity of ribonuclease H. In fact, high molecular weight c-myc RNA species were found to have accumulated in antisense-treated KYO1 cells. Control sense and scrambled antisense morpholino analogs did not inhibit MYC protein expression or induce the appearance of the anomalous RNA and protein bands. Molecular analyses by RT-PCR and sequencing revealed that the morpholino antisense effector had (1) inhibited splicing of the c-myc pre-mRNA, (2) induced missplicing of the pre-mRNA, and (3) inhibited translation of normal spliced c-myc mRNA. Identical results were obtained with acute promyelocytic leukemia, acute lymphoblastic leukemia, and histiocytic lymphoma cell lines.
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PMID:Antisense morpholino oligonucleotide analog induces missplicing of C-myc mRNA. 1035 27