Selection of effective antisense oligodeoxynucleotides with a green fluorescent protein-based assay. Discovery of selective and potent inhibitors of glutathione S-transferase Mu expression.
Antisense oligodeoxynucleotides (AS-ODNs) are frequently used for the down-regulation of protein expression. Because the majority of potential antisense sequences lacks effectiveness, fast screening methods for the selection of effective AS-ODNs are needed. We describe a new cellular screening assay for the evaluation of the potency and specificity of new antisense sequences. Fusion constructs of the gene of interest and the gene encoding the enhanced green fluorescent protein (EGFP) are cotransfected with AS-ODNs to COS-7 cells. Subsequently, cells are analysed for expression of the EGFP fusion protein by flow cytometry. With the assay, we tested the effectiveness of a set of 15 phosphorothioate ODNs against rat glutathione S-transferase Mu1 (GSTM1) and/or Mu2 (GSTM2). We found several AS-ODNs that demonstrated potent, sequence-specific, and concentration-dependent inhibition of fusion protein expression. At 0.5 microm, AS-6 and AS-8 inhibited EGFP-GSTM1 expression by 95 +/- 4% and 81 +/- 6%, respectively. AS-5 and AS-10 were selective for GSTM2 (82 +/- 4% and 85 +/- 0.4% decrease, respectively). AS-2 and AS-3, targeted at homologous regions in GSTM1 and GSTM2, inhibited both isoforms (77-95% decrease). Other AS-ODNs were not effective or displayed non-target-specific inhibition of protein expression. The observed decrease in EGFP expression was accompanied by a decrease in GSTM enzyme activity. As isoform-selective, chemical inhibitors of GSTM and GSTM knock-out mice are presently unavailable, the selected AS-ODNs constitute important tools for the study of the role of GSTM in detoxification of xenobiotics and protection against chemical-induced carcinogenesis.
't Hoen
Peter A C
PA
Division of Biopharmaceutics, Leiden/Amsterdam Center for Drug Research, The Netherlands.
Rosema
Bram-Sieben
BS
Commandeur
Jan N M
JN
Vermeulen
Nico P E
NP
Manoharan
Muthiah
M
van Berkel
Theo J C
TJ
Biessen
Eric A L
EA
Bijsterbosch
Martin K
MK
D000818:Animals; D019556:COS Cells; D003001:Cloning, Molecular; D015870:Gene Expression / Q000187:drug effects; D005982:Glutathione Transferase / Q000096:biosynthesis*; D049452:Green Fluorescent Proteins; D007527:Isoenzymes; D008164:Luminescent Proteins / Q000235:genetics; D020319:Oligodeoxyribonucleotides, Antisense / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D051381:Rats
D005982:Glutathione Transferase; D049452:Green Fluorescent Proteins; D007527:Isoenzymes; D008164:Luminescent Proteins; D020319:Oligodeoxyribonucleotides, Antisense