Formation of nuclear matrix filaments by p27(BBP)/eIF6.
p27(BBP)/eIF6 is an evolutionarily conserved protein necessary for ribosome biogenesis which was cloned in mammals for its ability to bind the cytodomain of beta 4 integrin. In cultured cells, a conspicuous fraction of p27(BBP)/eIF6 is associated with the intermediate filaments/nuclear matrix (IF/NM) cytoskeleton. The mechanism of this association is not known. Here we show that in epidermis p27(BBP)/eIF6 is naturally associated with IF/NM. To analyze the intrinsic capability of p27(BBP)/eIF6 to generate cytoskeletal networks, the properties of the pure, recombinant, untagged protein were studied. Recombinant p27(BBP)/eIF6 binds beta 4 integrin. Upon dialysis against IF buffer, p27(BBP)/eIF6 forms polymers which, strikingly, have a morphology identical to NM filaments. Cross-linking experiments suggested that polymerization is favored by the formation of disulphide bridges. These data suggest that p27(BBP)/eIF6 is associated with the cytoskeleton, and contributes to formation of NM filaments. These findings help to settle the controversy on nuclear matrix.
Ceci
Marcello
M
University Vita-Salute San Raffaele School of Medicine, Milan, Italy.
Offenhäuser
Nina
N
Marchisio
Pier Carlo
PC
Biffo
Stefano
S
D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism*; D007381:Intermediate Filament Proteins / Q000378:metabolism*; D051379:Mice; D015530:Nuclear Matrix / Q000378:metabolism* / Q000648:ultrastructure; D010448:Peptide Initiation Factors; D011994:Recombinant Proteins / Q000378:metabolism
D002352:Carrier Proteins; D007381:Intermediate Filament Proteins; C115811:Itgb4bp protein, mouse; D010448:Peptide Initiation Factors; D011994:Recombinant Proteins