Synthesis of low molecular weight ribonucleic acid in tumour cells

• Published in: Journal of molecular biology Vol. 28; no. 2; pp. 357 - 371
• Main Authors: Burdon, R.H., Martin, B.T., Lal, B.M.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.01.1967
• Subjects: Animals; Carcinoma, Krebs 2 - metabolism; Cell Nucleus - enzymology; Chromatography, Gel; Kinetics; Methionine - metabolism; Methylation; Molecular Weight; Phosphoric Monoester Hydrolases; RNA, Neoplasm - analysis; RNA, Neoplasm - biosynthesis; Transferases; Tritium; Ultracentrifugation; Uridine - metabolism
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/S0022-2836(67)80015-9

When [G- 3H]uridine incorporation into low molecular weight RNA of Krebs II ascites tumour cells is followed under conditions where the conversion of [ 3H]uridine derivatives to [ 3H]cytidine derivatives is prevented, no evidence could be obtained for actinomycin D-resistant synthesis of any specific low molecular weight RNA, nor any to suggest that 3'-terminal uridylate residues of any low molecular weight RNA species had a high turnover rate compared with the remainder of the molecule. The kinetics of incorporation of radioactivity from [G- 3H]uridine and L-[ methyl- 14C]methionine into low molecular weight RNA extracted from Krebs II cells with cold phenol suggest the existence of “methyl-deficient” intermediates in a process leading to the formation of 4 s RNA. Comparison of the labelled RNA components extracted from isolated Krebs II cell nuclei and cytoplasm using phenol, subsequent to detergent treatment, demonstrated that whereas the low molecular weight RNA components corresponding to 4 s RNA, or its putative precursors, are either present in very low amounts, or absent from the nuclear preparations, the cytoplasmic preparations yield results identical to those obtained using RNA extracted from whole cells with cold phenol. Examination of the intracellular distribution of the nucleic acid methylating enzymes has demonstrated that sRNA-transmethylase activity appears predominantly located in the cytoplasm, especially in the cell sap, whereas the DNA-transmethylase seems to be fairly firmly bound to the “chromatin” fraction of the nucleus.