title: The effects of histidine starvation on the methylation of ribosomal RNA.
abstract: The effect of amino acid starvation on the control of ribosome biosynthesis at the post-transcriptional level has been studied in Ehrlich ascites cells. A comparison of the turnover rates of ribosomal precursor RNA (pre-rRNA) and the degree of methylation of ribosomal RNA after histidine deprivation revealed that the slow down of ribosome formation is accompanied by a significant inhibition of rRNA methylation. Analysis of nucleolar and cytoplasmic RNA double-labelled with L-[Me-3H]methionine and [14C]uridine, as well as a quantitative determination of alkali-stable dinucleotides on DEAE-Sephadex, showed that methylation of rRNA species was inhibited by about 50% under shift-down conditions. This decrease in RNA methylation does not reflect an inhibition of rRNA methylases caused by amino acid starvation but is rather brought about by a shrinkage in the pool size of S-adenosylmethionine, the donor of methyl groups. It is suggested that amino acid starvation might exert its blocking effect on proper ribosome maturation by affecting the methylation of 45-S RNA.
mesh_terms: D000818:Animals; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism*; D002466:Cell Nucleolus / Q000201:enzymology; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D006639:Histidine / Q000378:metabolism* / Q000494:pharmacology; D051379:Mice; D011061:Poly A / Q000032:analysis; D011132:Polyribosomes / Q000378:metabolism; D012335:RNA, Ribosomal / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D012359:tRNA Methyltransferases / Q000378:metabolism*
chemical_list: D012335:RNA, Ribosomal; D011061:Poly A; D006639:Histidine; D012359:tRNA Methyltransferases; D012321:DNA-Directed RNA Polymerases