Hostname: page-component-7c8c6479df-24hb2 Total loading time: 0 Render date: 2024-03-28T17:44:57.009Z Has data issue: false hasContentIssue false

Box C/D snoRNA-associated proteins: Two pairs of evolutionarily ancient proteins and possible links to replication and transcription

Published online by Cambridge University Press:  01 June 2000

DONNA R. NEWMAN
Affiliation:
Department of Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, USA
JEFFREY F. KUHN
Affiliation:
Department of Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, USA
GAMILA M. SHANAB
Affiliation:
Department of Biochemistry, Ain Shams University, Cairo, Egypt
E. STUART MAXWELL
Affiliation:
Department of Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, USA
Get access

Abstract

The eukaryotic nucleolus contains a diverse population of small nucleolar RNAs (snoRNAs) essential for ribosome biogenesis. The box C/D snoRNA family possesses conserved nucleotide boxes C and D that are multifunctional elements required for snoRNA processing, snoRNA transport to the nucleolus, and 2′-O-methylation of ribosomal RNA. We have previously demonstrated that the assembly of an snoRNP complex is essential for processing the intronic box C/D snoRNAs and that specific nuclear proteins associate with the box C/D core motif in vitro. Using a box C/D motif derived from mouse U14 snoRNA, we have now affinity purified and defined four mouse proteins that associate with this minimal RNA substrate. These four proteins consist of two protein pairs: members of each pair are highly related in sequence. One protein pair corresponds to the essential yeast nucleolar proteins Nop56p and Nop58p. Affinity purification of mouse Nop58 confirms observations made in yeast that Nop58 is a core protein of the box C/D snoRNP complex. Isolation of Nop56 using this RNA motif defines an additional snoRNP core protein. The second pair of mouse proteins, designated p50 and p55, are also highly conserved among eukaryotes. Antibody probing of nuclear fractions revealed a predominance of p55 and p50 in the nucleoplasm, suggesting a possible role for the p50/p55 pair in snoRNA production and/or nucleolar transport. The reported interaction of p55 with TATA-binding protein (TBP) and replication A protein as well as the DNA helicase activity of p55 and p50 may suggest the coordination of snoRNA processing and snoRNP assembly with replication and/or transcriptional events in the nucleus. Homologs for both snoRNA-associated protein pairs occur in Archaea, strengthening the hypothesis that the box C/D RNA elements and their interacting proteins are of ancient evolutionary origin.

Type
Research Article
Copyright
2000 RNA Society

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)