Abstract
Fibrillarin, one of the major proteins of the nucleolus, has methyltransferase
activity directing 2′-O-ribose methylation of rRNA and snRNAs and is
required for rRNA processing. The ability of the plant umbravirus,
groundnut rosette virus, to move long distances through the phloem, the
specialized plant vascular system, has been shown to strictly depend on the
interaction of one of its proteins, the ORF3 protein (protein encoded by open
reading frame 3), with fibrillarin. This interaction is essential for several
stages in the groundnut rosette virus life cycle such as nucleolar import of
the ORF3 protein via Cajal bodies, relocalization of some fibrillarin from the
nucleolus to cytoplasm, and assembly of cytoplasmic umbraviral ribonucleoprotein
particles that are themselves required for the long-distance
spread of the virus and systemic infection. Here, using atomic force
microscopy, we determine the architecture of these complexes as singlelayered
ringlike structures with a diameter of 18–22 nm and a height of
2.0±0.4 nm, which consist of several (n=6–8) distinct protein granules. We
also estimate the molar ratio of fibrillarin to ORF3 protein in the complexes
as approximately 1:1. Based on these data, we propose a model of the
structural organization of fibrillarin–ORF3 protein complexes and discuss
potential mechanistic and functional implications that may also apply to
other viruses.
Original language | English |
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Pages (from-to) | 932-937 |
Number of pages | 6 |
Journal | Journal of Molecular Biology |
Volume | 376 |
Issue number | 4 |
DOIs | |
Publication status | Published - 29 Feb 2008 |
Keywords
- Atomic force microscopy
- Fibrillarin
- Umbravirus
- Virus movement
- Protein complexes