title: Introduction of hidden breaks during rRNA maturation and ageing in Tetrahymena pyriformis.
abstract: The stability of Tetrahymena pyriformis cytoplasmic rRNAs and nuclear rRNA precursors has been studied by polyacrylamide gel electrophoresis under partly and completely denaturing conditions. Cytoplasmic 17-S rRNA (Mr = 0.66 X 10(6) consists of a continuous polynucleotide chain throughout its lifetime, whereas the bulk of 26-S rRNA (Mr = 1.2m X 10(6) dissociates upon denaturation. Two large fragments (F1, F2) of somewhat different molecular weights (Mr 0.63 X 10(6) and 0.58 X 10(6) and the small 5.8-S rRNA fragment (Mr about 50 000) are regularly observed. Some additional distinct minor fragments (F3-F6) are noted under certain preparative conditions, suggestive of artifactual origin. The following conclusions were made from the data obtained . (a) Newly synthesized 26-S rRNA molecules do not contain the 'central' hidden break (separating F1 and F2) until about 15 min after their appearance in the cytoplasm; however, they release during denaturation the 5.8-S and/or a short-lived 7-S fragment (Mr about 75 000) which might represent a direct precursor to the 5.8-S rRNA. (b) The immediate nuclear precursor to the 26-S rRNA (Mr 1.39 X 10(6) releases a small fragment of similar size (7 S). (c) The largest stable transcription product of the rDNA (pre-rRNA) does not contain any hidden break.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D008970:Molecular Weight; D009691:Nucleic Acid Denaturation; D009694:Nucleic Acid Precursors / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000378:metabolism*; D013769:Tetrahymena pyriformis / Q000378:metabolism*; D013997:Time Factors
chemical_list: D009694:Nucleic Acid Precursors; D012335:RNA, Ribosomal