Correlation between the activity of a 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole-insensitive puff and the synthesis of major heat-shock polypeptide, hsp70, in Chironomus thummi.
The induction of puff III-A3b, a major heat-shock puff in Chironomus thummi salivary cells, was insensitive to the transcription inhibitor 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), whereas no transcriptional activity could be detected at the other heat-shock puffs in the presence of this drug. In these conditions, a polypeptide with the same Mr and isoform pattern as those of the major heat-shock polypeptide, hsp70, was synthesized. These results suggest that hsp70 is encoded by locus III-A3b. In addition to DRB insensitivity, incorporation of [3H]UTP on puff III-A3b took place in an in vitro transcription assay under low-salt conditions (100 mM NaCl); no labelling could be detected at the other heat-shock puffs under these conditions. Although DRB has been reported as a specific inhibitor of RNA polymerase II-directed transcription, and although the low-salt conditions were not propitious for the activity of this enzyme, RNA polymerase II was detected on puff III-A3b and on the other heat-shock puffs by immunofluorescence with anti-RNA polymerase II antibodies.
Barettino
D
D
Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
Morcillo
G
G
Díez
J L
JL
Carretero
M T
MT
Carmona
M J
MJ
D000818:Animals; D002683:Chironomidae / Q000235:genetics*; D004004:Dichlororibofuranosylbenzimidazole / Q000494:pharmacology*; D004175:Diptera / Q000235:genetics*; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D005455:Fluorescent Antibody Technique; D006360:Heat-Shock Proteins / Q000096:biosynthesis*; D007814:Larva; D012313:RNA / Q000096:biosynthesis; D012263:Ribonucleosides / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects*
D006360:Heat-Shock Proteins; D012263:Ribonucleosides; D004004:Dichlororibofuranosylbenzimidazole; D012313:RNA