Open AccessT7 Early RNAs and Escherichia coli Ribosomal RNAs are Cut from Large Precursor RNAs In Vivo by Ribonuclease III
Author(s) -
John J. Dunn,
F. William Studier
Publication year - 1973
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.70.12.3296
Subject(s) - rna , rnase p , rnase mrp , ribosomal rna , biology , rnase h , ribonuclease iii , microbiology and biotechnology , ribonuclease , non coding rna , rnase ph , small nucleolar rna , 5s ribosomal rna , ribosome , biochemistry , gene , rna interference
The early region of T7 DNA is transcribed as a single unit in a Ribonuclease III-deficientE. coli strain to produce large molecules essentially identical to those producedin vitro byE. coli RNA polymerase. As with thein vitro RNAs, these molecules are cut by purified RNase IIIin vitro to produce the messenger RNAs normally observedin vivo . Thus, the normal pathway for producing the T7 early messenger RNAsin vivo appears to involve endonucleolytic cleavage by RNase III. The uninfected RNase III-deficient strain contains several RNAs not observed in the parent strain. Patterns of labelingin vivo suggest that the largest of these RNAs, about 1.8 × 106 daltons, may be a precursor to the 16S and 23S ribosomal RNAs. When this large molecule is treatedin vitro with purified RNase III, molecules the size of precursor 16S and 23S ribosomal RNAs are released; hybridization competition experiments also indicate that the 1.8 × 106 dalton RNA does indeed represent ribosomal RNA. Thus, RNase III cleavage seems to be part of the normal pathway for producing at least the 16S and 23S ribosomal RNAsin vivo . Several smaller molecules are also released from the 1.8 × 106 dalton RNA by RNase III, but it is not yet established whether any of these contain 5S RNA sequences.