title: 5,6-Dichloro-1-beta-D-ribofuranosylbenzimidazole inhibits transcription of the beta-hemoglobin gene in vivo at initiation.
abstract: The mechanism by which 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) inhibits transcription of the beta-major Hb gene in vivo was investigated in differentiated Friend erythroleukemic cells (FELC). Steady-state nuclear RNA from untreated and DRB-treated FELC was analyzed by the S1 nuclease assay using [32P]DNA probes labeled at their 3' end close to the site of transcription initiation. DRB severely inhibited transcription of full-length beta-major Hb mRNA precursor molecules and did not increase the production of short, promoter-proximal transcripts. In addition, nascent beta-major RNA transcripts were labeled with [alpha-32P]UTP in nuclei isolated from DRB-treated FELC and untreated FELC and hybridized to separate restriction fragments spanning the entire beta-major Hb gene. DRB inhibited transcription of the promoter-proximal and promoter-distal beta-Hb DNA restriction fragments uniformly by 75-80% and did not detectably increase the amount of short transcripts. Moreover, a brief reversal of the DRB inhibition in vivo increased the number of short, nascent, promoter-proximal beta-Hb transcripts apparently as a result of reinitiation. These data indicate that DRB inhibited transcription of the beta-major Hb gene in vivo at initiation.
mesh_terms: D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004004:Dichlororibofuranosylbenzimidazole / Q000494:pharmacology*; D005796:Genes / Q000187:drug effects*; D006454:Hemoglobins / Q000235:genetics*; D007700:Kinetics; D004915:Leukemia, Erythroblastic, Acute / Q000378:metabolism; D007942:Leukemia, Experimental / Q000378:metabolism; D051379:Mice; D010957:Plasmids; D012333:RNA, Messenger / Q000235:genetics; D012263:Ribonucleosides / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects*
chemical_list: D006454:Hemoglobins; D012333:RNA, Messenger; D012263:Ribonucleosides; D004004:Dichlororibofuranosylbenzimidazole