title: Amplification of ribosomal DNA in the nucleolus of vitamin B12-deficient Euglena cells.
abstract: In the nucleoli of vitamin B12-deprived Euglena cells there is a 10-fold amplification of rDNA which correlates with increased numbers of fibrillar centers in the hypertrophic nucleoli. This rDNA amplification was demonstrated by means of molecular hybridization using a specific cytoplasmic rRNA probe. Most of the amplified sequences appear as extrachromosomal copies which were observed without digestion of total cellular or nuclear Euglena DNA. Five different hybridizing sequences, three of high molecular weight and two of 19.0 and 11.5 kb, were identified. The rDNA repeat unit which contains the 11.5-kb transcriptible sequence is 19.0 kb in length and was always more abundant in the undigested total cellular DNA. The possible mechanisms involved in the induction of rDNA amplification in vitamin B12-deficient cells are discussed.
authors.affiliation: Département de Biochimie, Faculté de Pharmacie, Université de Paris-Sud, Chatenay-Malabry, France.
authors.forename: O
authors.initials: O
authors.lastname: Bertaux
authors.forename: C
authors.initials: C
authors.lastname: Mederic
authors.forename: R
authors.initials: R
authors.lastname: Valencia
mesh_terms: D000818:Animals; D015139:Blotting, Southern; D002455:Cell Division; D002466:Cell Nucleolus / Q000378:metabolism / Q000648:ultrastructure; D004275:DNA, Ribosomal / Q000235:genetics*; D005055:Euglena / Q000235:genetics* / Q000378:metabolism; D005784:Gene Amplification; D008854:Microscopy, Electron; D015347:RNA Probes; D012091:Repetitive Sequences, Nucleic Acid; D014806:Vitamin B 12 Deficiency / Q000378:metabolism
chemical_list: D004275:DNA, Ribosomal; D015347:RNA Probes