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pEg7, a new Xenopus protein required for mitotic chromosome condensation in egg extracts.

Cubizolles F, Legagneux V, Le Guellec R, Chartrain I, Uzbekov R, Ford C, Le Guellec K - J. Cell Biol. (1998)

Bottom Line: This maternal mRNA encodes a protein, pEg7, whose expression is strongly increased during oocyte maturation.A similar localization of pEg7 is observed when sperm chromatin is allowed to form mitotic chromosomes in cytostatic factor-arrested egg extracts.Biochemical experiments show that pEg7 associates with Xenopus chromosome-associated polypeptides C and E, two components of the 13S condensin.

View Article: PubMed Central - PubMed

Affiliation: Biologie et Génétique du Développement, CNRS UPR 41, Université de Rennes I, Campus de Beaulieu, 35042 Rennes cedex, France.

ABSTRACT
We have isolated a cDNA, Eg7, corresponding to a Xenopus maternal mRNA, which is polyadenylated in mature oocytes and deadenylated in early embryos. This maternal mRNA encodes a protein, pEg7, whose expression is strongly increased during oocyte maturation. The tissue and cell expression pattern of pEg7 indicates that this protein is only readily detected in cultured cells and germ cells. Immunolocalization in Xenopus cultured cells indicates that pEg7 concentrates onto chromosomes during mitosis. A similar localization of pEg7 is observed when sperm chromatin is allowed to form mitotic chromosomes in cytostatic factor-arrested egg extracts. Incubating these extracts with antibodies directed against two distinct parts of pEg7 provokes a strong inhibition of the condensation and resolution of mitotic chromosomes. Biochemical experiments show that pEg7 associates with Xenopus chromosome-associated polypeptides C and E, two components of the 13S condensin.

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Related in: MedlinePlus

pEg7 is required for  assembly of mitotic chromosomes in vitro. (Left) Samples  from high-speed mitotic extracts  (1 μl) were separated by SDS-PAGE, transferred to a nitrocellulose filter, and probed with  nonimmune immunoglobulins,  purified anti–pEg7 P1 or purified anti–pEg7 G antibodies as  indicated. (Right) Chromosomes were assembled in the  presence of IgG (a–c), purified  anti–pEg7 G antibodies (d–f),  or purified anti–pEg7 P1 antibodies (g–i). Samples were taken  at different time points and  fixed. DNA was stained with  ethidium bromide: (a, d, and g)  30 min, (b, e, and h) 60 min, (c, f,  and i) 120 min. Bar, 5 μm.
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Figure 5: pEg7 is required for assembly of mitotic chromosomes in vitro. (Left) Samples from high-speed mitotic extracts (1 μl) were separated by SDS-PAGE, transferred to a nitrocellulose filter, and probed with nonimmune immunoglobulins, purified anti–pEg7 P1 or purified anti–pEg7 G antibodies as indicated. (Right) Chromosomes were assembled in the presence of IgG (a–c), purified anti–pEg7 G antibodies (d–f), or purified anti–pEg7 P1 antibodies (g–i). Samples were taken at different time points and fixed. DNA was stained with ethidium bromide: (a, d, and g) 30 min, (b, e, and h) 60 min, (c, f, and i) 120 min. Bar, 5 μm.

Mentions: The immunolocalization of pEg7 on condensed chromatin suggests that the protein could be involved in the process of chromosome condensation. This issue was addressed by immunoblocking experiments using purified anti–pEg7 antibodies. We first verified the pattern of the proteins revealed by these antibodies in high-speed mitotic extracts. The Fig. 5 (left) shows that the purified G and P1 antibodies recognized essentially one 150-kD polypeptide in these extracts. This 150-kD protein was not detected by nonimmune immunoglobulins.


pEg7, a new Xenopus protein required for mitotic chromosome condensation in egg extracts.

Cubizolles F, Legagneux V, Le Guellec R, Chartrain I, Uzbekov R, Ford C, Le Guellec K - J. Cell Biol. (1998)

pEg7 is required for  assembly of mitotic chromosomes in vitro. (Left) Samples  from high-speed mitotic extracts  (1 μl) were separated by SDS-PAGE, transferred to a nitrocellulose filter, and probed with  nonimmune immunoglobulins,  purified anti–pEg7 P1 or purified anti–pEg7 G antibodies as  indicated. (Right) Chromosomes were assembled in the  presence of IgG (a–c), purified  anti–pEg7 G antibodies (d–f),  or purified anti–pEg7 P1 antibodies (g–i). Samples were taken  at different time points and  fixed. DNA was stained with  ethidium bromide: (a, d, and g)  30 min, (b, e, and h) 60 min, (c, f,  and i) 120 min. Bar, 5 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2132990&req=5

Figure 5: pEg7 is required for assembly of mitotic chromosomes in vitro. (Left) Samples from high-speed mitotic extracts (1 μl) were separated by SDS-PAGE, transferred to a nitrocellulose filter, and probed with nonimmune immunoglobulins, purified anti–pEg7 P1 or purified anti–pEg7 G antibodies as indicated. (Right) Chromosomes were assembled in the presence of IgG (a–c), purified anti–pEg7 G antibodies (d–f), or purified anti–pEg7 P1 antibodies (g–i). Samples were taken at different time points and fixed. DNA was stained with ethidium bromide: (a, d, and g) 30 min, (b, e, and h) 60 min, (c, f, and i) 120 min. Bar, 5 μm.
Mentions: The immunolocalization of pEg7 on condensed chromatin suggests that the protein could be involved in the process of chromosome condensation. This issue was addressed by immunoblocking experiments using purified anti–pEg7 antibodies. We first verified the pattern of the proteins revealed by these antibodies in high-speed mitotic extracts. The Fig. 5 (left) shows that the purified G and P1 antibodies recognized essentially one 150-kD polypeptide in these extracts. This 150-kD protein was not detected by nonimmune immunoglobulins.

Bottom Line: This maternal mRNA encodes a protein, pEg7, whose expression is strongly increased during oocyte maturation.A similar localization of pEg7 is observed when sperm chromatin is allowed to form mitotic chromosomes in cytostatic factor-arrested egg extracts.Biochemical experiments show that pEg7 associates with Xenopus chromosome-associated polypeptides C and E, two components of the 13S condensin.

View Article: PubMed Central - PubMed

Affiliation: Biologie et Génétique du Développement, CNRS UPR 41, Université de Rennes I, Campus de Beaulieu, 35042 Rennes cedex, France.

ABSTRACT
We have isolated a cDNA, Eg7, corresponding to a Xenopus maternal mRNA, which is polyadenylated in mature oocytes and deadenylated in early embryos. This maternal mRNA encodes a protein, pEg7, whose expression is strongly increased during oocyte maturation. The tissue and cell expression pattern of pEg7 indicates that this protein is only readily detected in cultured cells and germ cells. Immunolocalization in Xenopus cultured cells indicates that pEg7 concentrates onto chromosomes during mitosis. A similar localization of pEg7 is observed when sperm chromatin is allowed to form mitotic chromosomes in cytostatic factor-arrested egg extracts. Incubating these extracts with antibodies directed against two distinct parts of pEg7 provokes a strong inhibition of the condensation and resolution of mitotic chromosomes. Biochemical experiments show that pEg7 associates with Xenopus chromosome-associated polypeptides C and E, two components of the 13S condensin.

Show MeSH
Related in: MedlinePlus