Open AccessSites of transcription initiation in vivo on Xenopus laevis ribosomal DNA
Author(s) -
Ronald H. Reeder,
Barbara SollnerWebb,
Harvey L. Wahn
Publication year - 1977
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.74.12.5402
Subject(s) - xenopus , transcription (linguistics) , biology , ribosomal rna , microbiology and biotechnology , dna , rna , genetics , chemistry , gene , linguistics , philosophy
We report the results of a novel method for locating sites of transcription initiation using a complex of capping enzymes from vaccinia virions that catalyze the reaction pppG +S -adenosylmethionine + (p)ppXpYpZp →7m GpppXpYpZp [Ensinger, M. J., Martin, S. A., Paoletti, E. and Moss, B. (1975)Proc. Natl. Acad. Sci. USA 72, 2525-2529]. This enzyme complex will cap di- or triphosphate termini but will not cap monophosphate or hydroxyl termini.Xenopus laevis 40S precursor rRNA from oocytes is capped by these enzymes, and we conclude that it has 5′-polyphosphate termini. Therefore, 40S RNA must represent the primary transcript of amplifiedX. laevis ribosomal DNA. The majority of 40S molecules with polyphosphate termini begin with the sequence (p)ppAAG. There is evidence, however, that the 5′ terminus may be heterogeneous. The majority of all detectable initiation events were localized close to the region coding for the 5′ end of the 40S RNA. No initiation sites were detected in the nontranscribed spacer, but an apparent initiation site in the middle of the transcribed region was also observed.