XB-ART-8550Mol Cell Biol September 1, 2001; 21 (18): 6210-21.
Xenopus U3 snoRNA GAC-Box A'' and Box A sequences play distinct functional roles in rRNA processing.
Mutations in the 5'' portion of Xenopus U3 snoRNA were tested for function in oocytes. The results revealed a new cleavage site (A0) in the 3'' region of vertebrate external transcribed spacer sequences. In addition, U3 mutagenesis uncoupled cleavage at sites 1 and 2, flanking the 5'' and 3'' ends of 18S rRNA, and generated novel intermediates: 19S and 18.5S pre-rRNAs. Furthermore, specific nucleotides in Xenopus U3 snoRNA that are required for cleavages in pre-rRNA were identified: box A is essential for site A0 cleavage, the GAC-box A'' region is necessary for site 1 cleavage, and the 3'' end of box A'' and flanking nucleotides are required for site 2 cleavage. Differences between metazoan and yeast U3 snoRNA-mediated rRNA processing are enumerated. The data support a model where metazoan U3 snoRNA acts as a bridge to draw together the 5'' and 3'' ends of the 18S rRNA coding region within pre-rRNA to coordinate their cleavage.
PubMed ID: 11509664
PMC ID: PMC87338
Article link: Mol Cell Biol
References [+] :
Ajuh, Xenopus borealis and Xenopus laevis 28S ribosomal DNA and the complete 40S ribosomal precursor RNA coding units of both species. 1991, Pubmed, Xenbase