Chromosome activity and cell function in polytenic cells

Clever, Ulrich; Storbeck, Ingrid; Romball, Carol G.

doi:10.1016/0014-4827(69)90563-1

Cited by 39 publications

(1 citation statement)

References 15 publications

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“…As the salivary protein synthesis in these cells comprise more than 80% of total protein synthesis (23), it can be anticipated that the corresponding messenger RNAs are major nonribosomal, high molecular weight RNA species. Furthermore, since not even a 24-hr inhibition of RNA synthesis substantially influences salivary protein synthesis (24)(25)(26), the messengers are probably also stable or turning over very slowly. In the present investigation, absorbance measurements showed that 75S RNA constitutes as much as 1.5% of total RNA.…”

Section: Methodsmentioning

confidence: 99%

Evidence for Transport of 75S RNA from a Discrete Chromosome Region via Nuclear Sap to Cytoplasm in Chironomus tentans

Daneholt

Hosick

1973

Proc. Natl. Acad. Sci. U.S.A.

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Salivary glands of the dipteran Chironomus tentans were exposed to tritiated pyrimidines for different time periods either in vitro or in vivo. Nonribosomal, high molecular weight RNA molecules of very different sizes (15-100 S) were labeled on chromosomes I-III, while only one main species, 75S RNA, was recorded in Balbiani ring 2, a giant chromosome puff on chromosome IV. 75S RNA was present as a prominent fraction in nuclear sap, but not in cytoplasm, after 90 min of incubation in vitro. During the ensuing 90 min, 75S RNA also appeared in cytoplasm. After 1 week of labeling in vivo, radioactive 75S RNA accumulated heavily in cytoplasm. Absorbance measurements showed that 75S RNA constituted as much as 1.5% of the total salivary-gland RNA. The half-life of 75S RNA was estimated to exceed 35 hr.Available data on the intracellular distribution and metabolic stability of nonribosomal, high molecular weight RNA from Balbiani ring 2 and chromosomes I-III indicate that most of the cytoplasmic 75S RNA is transcribed in the Balbiani ring 2 region of chromosome IV. 75S RNA molecules are, therefore, likely to be transferred from Balbiani ring 2, via nuclear sap, to cytoplasm without being measurably reduced in molecular size.One important step in gene expression of eukaryotic cells is the transfer of genetic information from nuclear DNA to polysomes in cytoplasm. Available data strongly indicate that this information transfer is accomplished by RNA, but the details of the process are far from clear (1). Although different defined messenger RNA species have been demonstrated in cytoplasm (2-5), it has been more difficult to identify the individual corresponding precursors in the nucleus. The main reason for this failure is that the nonribosomal, high molecular weight RNA of the nucleus is a complex mixture of molecules, with concomitant identification problems. In transformed cells, it is feasible to select for one type of RNA, the virusspecific RNA, and thus simplify the analysis (6-8). Another approach is to extensively fractionate the nucleus in order to obtain defined, nonribosomal, high molecular weight RNA species. When such a procedure was applied recently to salivary gland cells of the midge Chironomus tentans, a defined RNA species (75S RNA) was recorded in a restricted chromosome region (9). The present investigation shows that it is possible to follow the migration of that particular RNA species from its site of synthesis via nuclear sap to cytoplasm. Proc. Nat. Acad. Sci. USA 70 (1973) containing labeled, ethanol-soluble substances that would disturb the radioactivity pattern unless extracted), each sample was treated with 100 Al of SDS-Pronase solution.RNA was then precipitated overnight at -20°after 10 Al of 1 M NaCl and 250 ,l of 100% ethanol had been added. Electrophoresis. The technique with agarose gel slabs has been described in detail (13). 1% Agarose gels were prepared in 0.02 M Tris -HCl (pH 8.0)-2 mg/ml of SDS-0.02 M NaCl-2 mM EDTA. After completion of electrophoresis, the gel was cut in...

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Section: Methodsmentioning

confidence: 99%