title: Adenosine analogue induced ultrastructural changes in the nucleolus that correlate with inhibition of ribosomal RNA processing.
abstract: The aminonucleotide of puromycin (AMS) is known to have a differential effect on ribosomal RNA (rRNA) synthesis and the cell-cycle traverse in normal as compared to neoplastic or virally transformed cells. In this study, AMS and its demethylated derivative, 3'-amino-3'-deoxyadenosine (3'-AmA) have been used to compare their effects on normal (IMR 90) versus transformed (AG 2804) human fibroblasts with regard to preribosomal RNA (pre-rRNA) transcription, the processing of this RNA, and structural changes in the nucleolus. The processing of pre-rRNA in normal and transformed fibroblasts treated with 3'-AmA for 4 hr was markedly depressed. However, this process did not appear to be affected by the AMS treatment of normal cells, while in transformed cells it was maximally inhibited within 4 hr of exposure to this drug. Ultrastructural changes were observed in the nucleoli of normal and transformed cells treated with 3'-AmA, whereas treatment of these cells with AMS produced alterations of nucleolar structure only in the transformed cells. These changes correlated with the onset of inhibition of pre-rRNA processing. Our findings suggest that the impairment of pre-rRNA processing produced by AMS and 3'-AmA in transformed cells and by 3'-AmA in normal cells may be due to structural disorganization of the nucleolus produced by these antimetabolites.
mesh_terms: D002466:Cell Nucleolus / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D002472:Cell Transformation, Viral; D003839:Deoxyadenosines / Q000031:analogs & derivatives* / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D008168:Lung; D009694:Nucleic Acid Precursors / Q000378:metabolism; D011691:Puromycin / Q000031:analogs & derivatives*; D011692:Puromycin Aminonucleoside / Q000494:pharmacology*; D012322:RNA Precursors; D012323:RNA Processing, Post-Transcriptional / Q000187:drug effects*; D012335:RNA, Ribosomal / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D003839:Deoxyadenosines; D009694:Nucleic Acid Precursors; D012322:RNA Precursors; D012335:RNA, Ribosomal; C019247:3'-amino-3'-deoxyadenosine; D011691:Puromycin; D011692:Puromycin Aminonucleoside