Phosphorylation of p27(BBP)/eIF6 and its association with the cytoskeleton are developmentally regulated in Xenopus oogenesis.
p27BBP/eIF6 is an evolutionarily conserved regulator of ribosomal function. It is necessary for 60S biogenesis and impedes improper joining of 40S and 60S subunits, regulated by protein kinase C or Efl1p. No data on p27BBP/eIF6 during early development of Metazoa are available. We studied the distribution, post-translational changes and association with the cytoskeleton of p27BBP/ eIF6 during Xenopus oogenesis and early development. Results indicate that p27BBP/eIF6 is present throughout oogenesis, partly associated with 60S subunits, partly free and with little cytoskeleton bound. During prophase I, p27BBP/eIF6 is detected as a single band of 27-kDa. Upon maturation induced by progesterone or protein kinase C, a serine-phosphorylated 29 kDa isoform appears and is kept throughout development to the neurula stage. Confocal microscopy showed that the distribution of p27BBP/eIF6 and its association with the cytoskeleton varies according to oogenesis stages. Briefly, in stage 6 oocytes, p27BBP/eIF6 has a limited dot-like distribution, and does not co-localize with cytokeratin, whereas upon maturation it spreads throughout the cytoplasm. After fertilization, a large fraction coalesces around cytomembranes and a cytochalasin B-sensitive co-localization with cytokeratin occurs. RNAse removes p27BBP/eIF6 from the cytokeratin fibres. Developmental data suggest a role of p27BBP/eIF6 in controlling ribosomal availability or regulating cross-talk between ribosomes and the cytoskeleton.
Dipartimento di Biologia Strutturale e Funzionale, Università di Napoli Federico II, Napoli, Italy.
R
R
Carotenuto
N
N
De Marco
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S
Biffo
M
M
Wilding
M C
MC
Vaccaro
P C
PC
Marchisio
T
T
Capriglione
G L
GL
Russo
C
C
Campanella
D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D039642:Eukaryotic Initiation Factors; D005260:Female; D007150:Immunohistochemistry; D007381:Intermediate Filament Proteins / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D008540:Meiosis; D018613:Microscopy, Confocal; D008970:Molecular Weight; D009865:Oocytes / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D009866:Oogenesis; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D011374:Progesterone / Q000494:pharmacology; D011485:Protein Binding; D012270:Ribosomes / Q000378:metabolism; D013997:Time Factors; D029867:Xenopus Proteins / Q000737:chemistry / Q000378:metabolism*; D014982:Xenopus laevis; D015053:Zygote / Q000378:metabolism
D002352:Carrier Proteins; C109284:EIF6 protein, human; D039642:Eukaryotic Initiation Factors; D007381:Intermediate Filament Proteins; D029867:Xenopus Proteins; C504182:eIF6 protein, Xenopus; D010768:Phosphoserine; D011374:Progesterone; D010744:Phosphoric Monoester Hydrolases