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A predominant basic α‐tubulin isoform present in prophase Xenopus oocyte decreases during meiotic maturation
Author(s) -
Thibier Catherine,
Denoulet Philippe,
Jessus Catherine,
Ozon René
Publication year - 1992
Publication title -
biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 85
eISSN - 1768-322X
pISSN - 0248-4900
DOI - 10.1016/0248-4900(92)90138-q
Subject(s) - xenopus , biology , prophase , gene isoform , tubulin , oocyte , meiosis , microbiology and biotechnology , metaphase , microtubule , maturation promoting factor , mitosis , cytoskeleton , biochemistry , cyclin dependent kinase 1 , cell cycle , embryo , gene , cell , chromosome
Summary— Xenopus oocytes are blocked in prophase of the first meiotic division. During the G2/M transition drastic changes occur both in the cytoskeletal organization and in the capacity of tubulin to polymerize. Posttranslational modification of tubulin isoforms might be one of the factors that control the dynamic properties of microtubules. We have therefore analysed, by two‐dimensional polyacrylamide gel electrophoresis, the isotubulins purified from Xenopus oocytes, and we show that tubulin is resolved into at least four α‐isoforms and four β‐isoforms. We have identified a basic α (α b )‐tubulin isoform which is specific to prophase arrested oocyte and that progressively disappears during meiotic maturation; its decrease is initiated when the nuclear envelope breaks down and is controlled by the nucleus. Using 35S methionine labelled oocytes we demonstrate that the disappearance of the α b isotubulin results from both an arrest of its biosynthesis after maturation, and from posttranslational modification which induces a shift of this α‐isoform to a more acidic p I . Moreover, in vitro experiments using 35S prelabelled tubulin purified from prophase oocytes show that metaphase extracts containing MPF activity are able to induce the acidification of the α b ‐isoform, suggesting that the observed post‐translational modification might be regulated by p34 cdc2 . However, the nature of this modification remains to be elucidated.