SDS patient cell lines show decreased ribosomal RNA synthesis. (A) Healthy control and SDS patient (DF250) primary fibroblasts were metabolically labeled with 32P-orthophosphate for 75 minutes and chased with 25 mM phosphate for the indicated times in hours. RNA was extracted at the indicated time points, resolved on a 1% agarose/formaldehyde gel, and stained with ethidium bromide. (B) RNA from the gel in panel A was transferred to a nylon membrane and analyzed by autoradiography. The positions of the 45S and 32S rRNA precursor rRNAs and of the mature 28S, 18S, and 5.8S rRNAs are indicated. (C) Lysates from normal control primary fibroblasts or SDS patient primary fibroblasts were sedimented through sucrose gradients as in Figure 6D. This experiment was repeated for a total of 3 independent experiments. No consistent difference in the ratios of the 40S, 60S, and 80S peaks was noted.
