title: Messenger RNA regulation in humam diploid fibroblasts.
abstract: In resting, non-growing human diploid fibroblasts the amount of rRNA is reduced 1.8-fold, cytoplasmic polysomes are disaggregated, and the level of poly-A RNA (mRNA) is reduced 1.8-fold in relation to growing cells. The distribution of poly-A RNA is altered in resting, non-growing cells so that an average of 64% of the total cytoplasmic poly-A RNA sediments along with particles  lighter than 80S (prepolysomal) in sucrose density gradients. By camparison, in growing cells only 30% of the cytoplasmic poly-A RNA sediments in the prepolysomal region. In SDS sucrose gradients, the sedimentation profile of the prepolysomal poly-A RNA from resting cells resembles that of polysomal poly-A RNA from those cells. In contrast, the average size of prepolysomal poly-A RNA from growing cells is much smaller than that of the polysomal poly-A RNA from those cells. These data are compatible with the possibility that resting cell prepolysomal poly-A is untranslated mRNA. Also consistent with this interpretation are experiments which demonstrate that one-quarter to one-third of the prepolysomal poly-A RNA of resting cells is recruited into polysomes in the presence of of cyoloheximide.
mesh_terms: D002455:Cell Division; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D004171:Diploidy; D005347:Fibroblasts / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D008954:Models, Biological; D011061:Poly A / Q000032:analysis; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D012335:RNA, Ribosomal; D011061:Poly A; D003513:Cycloheximide