Synthese und Umsatz von Ribonukleinsäuren in suspendierten Säugetierzellen / Synthesis and Turnover of Ribonucleic Acids in Suspended Mammalian Cells

Abstract

The influence of ionizing radiation on the turnover of high molecular weight RNA in mammalian cells was studied. Growing cultures of suspended human amnion cells were labeled with 32P and irradiated with different doses of X-rays. RNA was isolated by hot phenol and the high molecular weight RNA fractionated by chromatography on methylated serum albumin celite columns. The salt gradient eluted RNA with sedimentation coefficients of 16 S or greater, which were characterized by analysis of nucleotide composition. Irradiation with doses from 900—6000 R results in degradation of pre-labeled RNA. A quantitative determination reveals that more 32P-radioactivity leaves the high molecular weight RNA compared to labeled total material that is degraded to acid soluble products. This indicates that RNA is partly broken down to low molecular weight fragments. Nucleotide analysis of the high molecular weight RNA fractions indicate a preferred degradation of ribosomal precursor RNA. The experimental results give evidence that the analysis of RNA synthesis for a certain period after irradiation is complicated by interfering processes like the simultaneous degradation of RNA.