The spacing between functional Cis-elements of U3 snoRNA is critical for rRNA processing.
J Mol Biol
; 300(1): 57-74, 2000 Jun 30.
Article
en En
| MEDLINE
| ID: mdl-10864498
ABSTRACT
The sequences and structural features of Xenopus laevis U3 small nucleolar RNA (snoRNA) necessary for pre-rRNA cleavage at sites 1 and 2 to form 18 S rRNA were assayed by depletion/rescue experiments in Xenopus oocytes. Mutagenesis results demonstrated that the putative stem of U3 domain I is unnecessary for 18 S rRNA processing. A model consistent with earlier experimental data is proposed for the structure of domain I when U3 is not yet bound to pre-rRNA. For its function in rRNA processing, a newly discovered element (5' hinge) was revealed to be important but not as critical as the 3' hinge region in Xenopus U3 snoRNA for 18 S rRNA formation. Base-pairing is proposed to occur between the U3 5' hinge and 3' hinge and complementary regions in the external transcribed spacer (ETS); these interactions are phylogenetically conserved, and are homologous to those previously described in yeast (5' hinge-ETS) and trypanosomes (3' hinge-ETS). A model is presented where the base-pairing of the 5' hinge and 3' hinge of U3 snoRNA with the ETS of pre-rRNA helps to correctly position U3 boxes A'+A for their function in rRNA processing. Like an earlier proposal for yeast, boxes A' and A of Xenopus may base-pair with 18 S sequences in pre-rRNA. We present the first direct experimental evidence in any system that box A' is essential for U3 snoRNA function in 18 S rRNA formation. The analysis of insertions and deletions indicated that the spacing between the U3 elements is important, suggesting that they base-pair with the ETS and 18 S regions of pre-rRNA at the same time.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Xenopus laevis
/
Precursores del ARN
/
ARN Ribosómico 18S
/
Procesamiento Postranscripcional del ARN
/
ARN Nucleolar Pequeño
Límite:
Animals
Idioma:
En
Revista:
J Mol Biol
Año:
2000
Tipo del documento:
Article
País de afiliación:
Estados Unidos