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“Reverse torpedoes“ model for the termination and processing of U3 snoRNA
Author(s) -
Nazar Ross N.,
Nabavi Sadegh
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a1028-a
Subject(s) - polyadenylation , exonuclease , small nucleolar rna , transcription (linguistics) , biology , cleavage (geology) , rna , microbiology and biotechnology , antitermination , termination factor , dna , genetics , gene , non coding rna , polymerase , rna dependent rna polymerase , paleontology , linguistics , philosophy , fracture (geology)
While the termination of transcription and 3′ RNA processing of the eukaryotic mRNA has been linked to a polyadenylation signal and a transcript cleavage process, much less is known about the termination or processing of non polyadenylated pol II transcripts. An efficiently expressed plasmid‐based expression system was used to study the termination and processing of S. pombe U3 snoRNA transcripts in vivo . The termination assay was linked to cell transformation and restriction fragment length polymorphism was used to determine levels of plasmid‐derived U3 snoRNA. Mutation analyses in vivo indicate that the maturation of the 3′ end is not directly dependent on an external cis‐acting sequence or structure; rather, it is dependent on a transcript cleavage which can occur hundreds or even thousands of nucleotides downstream of the mature U3 snoRNA sequence. Similarly, termination is dependent on transcript cleavage which is localized in a hairpin structure that normally follows the 3′ end of the U3 snoRNA but, which also can be moved hundreds or thousands of nucleotides downstream. Both processes, however, can be induced simultaneously and equally efficiently with a single unrelated Pac 1 endonuclease‐labile structure. The results support a “reverse torpedoes” model in which a single cleavage allows exonuclease access to the transcript leading to transcription termination in one direction and RNA maturation in the other direction. Supported by the Natural Sciences and Engineering Research Council of Canada.