The Balbiani Rings (BR) in the polytene chromosomes of Chironomus salivary glands are intense sites of transcription. The nascent RNPs fold during transcription into 40-50-nm granules, containing in the mature transcript approximately 37-kb RNA. Using a new nucleic acid specific stain, osmium ammine B on Lowicryl sections, in combination with electron energy filtered imaging of sections containing BR granules, we demonstrate a RNA-rich particulate substructure (10-nm particle diameter; 10-12 particles per BR granule). Elemental imaging supports that these particles are enriched in phosphorus. The possible relationship of these RNA-rich particles to ribonucleosomes is discussed, as well as models for their arrangement in the mature BR granules.
Balbiani ring hnRNP substructure visualized by selective staining and electron spectroscopic imaging.
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A L Olins, D E Olins, D P Bazett-Jones; Balbiani ring hnRNP substructure visualized by selective staining and electron spectroscopic imaging.. J Cell Biol 1 May 1992; 117 (3): 483–491. doi: https://doi.org/10.1083/jcb.117.3.483
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