Sea urchin vault structure, composition, and differential localization during development.
BACKGROUND
Vaults are intriguing ribonucleoprotein assemblies with an unknown function that are conserved among higher eukaryotes. The Pacific coast sea urchin, Strongylocentrotus purpuratus, is an invertebrate model organism that is evolutionarily closer to humans than Drosophila and C. elegans, neither of which possesses vaults. Here we compare the structures of sea urchin and mammalian vaults and analyze the subcellular distribution of vaults during sea urchin embryogenesis.


RESULTS
The sequence of the sea urchin major vault protein (MVP) was assembled from expressed sequence tags and genome traces, and the predicted protein was found to have 64% identity and 81% similarity to rat MVP. Sea urchin MVP includes seven approximately 50 residue repeats in the N-terminal half of the protein and a predicted coiled coil domain in the C-terminus, as does rat MVP. A cryoelectron microscopy (cryoEM) reconstruction of isolated sea urchin vaults reveals the assembly to have a barrel-shaped external structure that is nearly identical to the rat vault structure. Analysis of the molecular composition of the sea urchin vault indicates that it contains components that may be homologs of the mammalian vault RNA component (vRNA) and protein components (VPARP and TEP1). The sea urchin vault appears to have additional protein components in the molecular weight range of 14-55 kDa that might correspond to molecular contents. Confocal experiments indicate a dramatic relocalization of MVP from the cytoplasm to the nucleus during sea urchin embryogenesis.


CONCLUSIONS
These results are suggestive of a role for the vault in delivering macromolecules to the nucleus during development.
Stewart
Phoebe L
PL
Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA. phoebe.stewart@vanderbilt.edu
Makabi
Miriam
M
Lang
Jennifer
J
Dickey-Sims
Carrie
C
Robertson
Anthony J
AJ
Coffman
James A
JA
Suprenant
Kathy A
KA
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism / Q000648:ultrastructure; D020285:Cryoelectron Microscopy; D003593:Cytoplasm / Q000378:metabolism / Q000648:ultrastructure; D004591:Electrophoresis, Polyacrylamide Gel; D047108:Embryonic Development; D005260:Female; D008297:Male; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D029543:Nucleocytoplasmic Transport Proteins / Q000502:physiology; D017434:Protein Structure, Tertiary; D051381:Rats; D017386:Sequence Homology, Amino Acid; D047270:Strongylocentrotus purpuratus / Q000196:embryology* / Q000502:physiology; D020394:Vault Ribonucleoprotein Particles / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure*; D000099187:Major Vault Protein
D029543:Nucleocytoplasmic Transport Proteins; D020394:Vault Ribonucleoprotein Particles; D000099187:Major Vault Protein