RNA-Directed Actions of 8-Chloro-Adenosine in Multiple Myeloma Cells

Christine M. Stellrecht, Carlos O. Rodriguez, Mary Ayres, Varsha Gandhi

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48 Scopus citations


The purine analogue, 8-chloro-adenosine (8-Cl-Ado), induces apoptosis in a number of multiple myeloma (MM) cell lines. This ribonucleoside analogue accumulates as a triphosphate and selectively inhibits RNA synthesis without perturbing DNA synthesis. Cellular RNA is synthesized by one of three polymerases (Pol I, II, or III); thus, the inhibition of one or more RNA polymerases may be mediating 8-Cl-Ado cytotoxicity. Here, we have addressed this question by dissecting the RNA-directed actions of 8-Cl-Ado in MM cells. Differential alterations in [3H]uridine incorporation were found in the three major classes of RNA after a 20-h exposure with 10 μM 8-Cl-Ado. The synthesis rate of Pol III transcripts, 5 S and tRNA, remained unchanged, whereas Pol I-mediated rRNA synthesis decreased by ∼20%. In contrast, mRNA synthesis, which is transcribed by Pol II, rapidly declined within 4 h and reached a 50% decrease, which was maintained for 20 h. Parallel to RNA synthesis inhibition, 8-Cl-Ado was maximally incorporated in the mRNA (>13 nmol/mg RNA), which was 5-fold higher than the tRNA and rRNA incorporation. Electrophoretic and radiographic analysis of newly synthesized and processed [14C]uridine-labeled transcripts indicated that the analogue blocks transcription elongation. Consistent with that result, high-performance liquid chromatography analysis of micrococcal nuclease and spleen phosphodi-esterase-digested RNA demonstrated that the analogue incorporation is at the 3′ terminus. In conclusion, our data demonstrate that in MM cells, 8-Cl-Ado is preferentially incorporated into mRNA, suggesting a propensity toward Pol II, and inhibits RNA synthesis by premature transcriptional chain termination.

Original languageEnglish (US)
Pages (from-to)7968-7974
Number of pages7
JournalCancer Research
Issue number22
StatePublished - Nov 15 2003
Externally publishedYes

ASJC Scopus subject areas

  • Cancer Research
  • Oncology


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