Inhibition of T-cell proliferation by a MYB antisense oligomer is accompanied by selective down-regulation of DNA polymerase alpha expression.
We recently found that inhibition of MYB protein synthesis in human peripheral blood mononuclear cells (PBMC) exposed to human c-myb (designated MYB) antisense oligodeoxynucleotides prevents entry into S phase and cell proliferation. To determine the mechanism(s) by which down-regulation of human c-myb protein (MYB) synthesis interferes with DNA synthesis, we analyzed mRNA levels of DNA polymerase alpha and proliferating cell nuclear antigen (PCNA), transcripts of two genes required for DNA synthesis, in normal and leukemic T lymphocytes exposed to MYB antisense oligodeoxynucleotides. Expression of DNA polymerase alpha was inhibited both in normal T lymphocytes progressing from G0 to S phase and in exponentially growing CCRF-CEM leukemic cells, whereas expression of PCNA was inhibited only in mitogen-stimulated PBMC and remained essentially unaffected in the leukemia T-cell line. The functional link between expression of MYB and DNA polymerase alpha mRNAs was further demonstrated by analyzing DNA polymerase alpha mRNA levels in a temperature-sensitive (ts) fibroblast cell line (TK-ts13; TK is thymidine kinase) constitutively expressing human MYB mRNA driven by the simian virus 40 (SV40) promoter. In the MYB-expressing TK-ts13 cells, DNA polymerase alpha mRNA levels were unaffected following shift to the nonpermissive temperature of 39.6 degrees C, whereas in the parental line, DNA polymerase alpha mRNA levels were readily down-regulated. These findings indicate that the expression of MYB is related to that of DNA polymerase alpha in cells expressing MYB at high levels and suggest that there is a functional link between c-myb and DNA polymerase alpha mRNA expression during cell cycle progression of normal T lymphocytes.
Department of Pathology, Temple University Medical School, Philadelphia, PA 19140.
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Venturelli
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Travali
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Calabretta
D002455:Cell Division; D002460:Cell Line; D002478:Cells, Cultured; D004257:DNA Polymerase II / Q000235:genetics*; D004261:DNA Replication; D003609:Dactinomycin / Q000494:pharmacology; D006801:Humans; D007399:Interphase; D009687:Nuclear Proteins / Q000235:genetics; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D018809:Proliferating Cell Nuclear Antigen; D011505:Protein-Tyrosine Kinases / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D020598:Proto-Oncogene Proteins c-myb; D012313:RNA / Q000235:genetics; D016372:RNA, Antisense; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000235:genetics*; D013601:T-Lymphocytes / Q000166:cytology* / Q000201:enzymology; D013696:Temperature; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000187:drug effects / Q000201:enzymology
D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D018809:Proliferating Cell Nuclear Antigen; D011518:Proto-Oncogene Proteins; D020598:Proto-Oncogene Proteins c-myb; D016372:RNA, Antisense; D012333:RNA, Messenger; D003609:Dactinomycin; D012313:RNA; D011505:Protein-Tyrosine Kinases; D004257:DNA Polymerase II