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Rae1 is an essential mitotic checkpoint regulator that cooperates with Bub3 to prevent chromosome missegregation.

Babu JR, Jeganathan KB, Baker DJ, Wu X, Kang-Decker N, van Deursen JM - J. Cell Biol. (2003)

Bottom Line: Here we show that haplo-insufficiency of either Rae1 or Bub3 results in a similar phenotype involving mitotic checkpoint defects and chromosome missegregation.We also show that overexpression of Rae1 can correct for Rae1 haplo-insufficiency and, surprisingly, Bub3 haplo-insufficiency.Thus, our data demonstrate a novel function for Rae1 and characterize Rae1 and Bub3 as related proteins with essential, overlapping, and cooperating roles in the mitotic checkpoint.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN 55905, USA.

ABSTRACT
The WD-repeat proteins Rae1 and Bub3 show extensive sequence homology, indicative of functional similarity. However, previous studies have suggested that Rae1 is involved in the mRNA export pathway and Bub3 in the mitotic checkpoint. To determine the in vivo roles of Rae1 and Bub3 in mammals, we generated knockout mice that have these genes deleted individually or in combination. Here we show that haplo-insufficiency of either Rae1 or Bub3 results in a similar phenotype involving mitotic checkpoint defects and chromosome missegregation. We also show that overexpression of Rae1 can correct for Rae1 haplo-insufficiency and, surprisingly, Bub3 haplo-insufficiency. Rae1- and Bub3- mice are embryonic lethal, although cells from these mice did not have a detectable defect in nuclear export of mRNA. Unlike mice, compound haplo-insufficient Rae1/Bub3 mice are viable. However, cells from these mice exhibit much greater rates of premature sister chromatid separation and chromosome missegregation than single haplo-insufficient cells. Finally, we show that mice with mitotic checkpoint defects are more susceptible to dimethylbenzanthrene-induced tumorigenesis than wild-type mice. Thus, our data demonstrate a novel function for Rae1 and characterize Rae1 and Bub3 as related proteins with essential, overlapping, and cooperating roles in the mitotic checkpoint.

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DMBA-induced tumor formation in checkpoint-defective mice. (A) Gross photograph of lung tumors of a DMBA-treated Rae1+/−/Bub3+/− mouse (left), and a section of a Rae1+/−/Bub3+/− lung tumor (right; 10×, hematoxylin + eosin). Arrows point out the tumors. (B) The occurrence of lung tumors in 5-mo-old mice plotted as percentage incidence. The asterisk indicates P < 0.05 compared with wild-type mice by Chi-squared test. We note that the tumor incidence of the checkpoint-defective group of mice as a whole is significantly increased relative to wild-type mice (P < 0.05 by Chi-squared test). (C) The average number of lung adenomas per mouse (±SEM). The asterisks indicate P < 0.05 compared with wild-type mice by Wilcoxon rank sum test.
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fig9: DMBA-induced tumor formation in checkpoint-defective mice. (A) Gross photograph of lung tumors of a DMBA-treated Rae1+/−/Bub3+/− mouse (left), and a section of a Rae1+/−/Bub3+/− lung tumor (right; 10×, hematoxylin + eosin). Arrows point out the tumors. (B) The occurrence of lung tumors in 5-mo-old mice plotted as percentage incidence. The asterisk indicates P < 0.05 compared with wild-type mice by Chi-squared test. We note that the tumor incidence of the checkpoint-defective group of mice as a whole is significantly increased relative to wild-type mice (P < 0.05 by Chi-squared test). (C) The average number of lung adenomas per mouse (±SEM). The asterisks indicate P < 0.05 compared with wild-type mice by Wilcoxon rank sum test.

Mentions: To determine whether single and double haplo-insufficient mice have increased susceptibility to carcinogen-induced tumorigenesis, we gave pups from Rae1+/− x Bub3+/− intercrosses a single application of 50 μl of a solution of 0.5% DMBA in acetone to the dorsal surface on post-natal day 5 (Serrano et al., 1996). 5 mo after DMBA treatment, the mice were killed and screened for tumor formation. Irrespective of the mouse genotype, tumors were exclusively detectable in the lungs (Fig. 9 A). In Rae1+/−, Bub3+/−, and Rae1+/−/Bub3+/− mice, the incidence of lung tumors was increased compared with their wild-type counterparts (Fig. 9 B), as was the average number of tumors per treated animal (Fig. 9 C). As controls, we examined 10 nontreated 5-mo-old mice per genotype for spontaneous tumors. No tumors were found in the wild-type, Rae1+/−, or Bub3+/− mice, whereas 1 of the 10 Rae1+/−/Bub3+/− mice had a lung tumor. Taken together, the above data indicate that mitotic checkpoint–defective mice are predisposed to chemical-induced lung tumorigenesis. We are monitoring over 50 mice per genotype (currently ranging in age from 2 to 7 mo) for possible development of spontaneous tumors as they age.


Rae1 is an essential mitotic checkpoint regulator that cooperates with Bub3 to prevent chromosome missegregation.

Babu JR, Jeganathan KB, Baker DJ, Wu X, Kang-Decker N, van Deursen JM - J. Cell Biol. (2003)

DMBA-induced tumor formation in checkpoint-defective mice. (A) Gross photograph of lung tumors of a DMBA-treated Rae1+/−/Bub3+/− mouse (left), and a section of a Rae1+/−/Bub3+/− lung tumor (right; 10×, hematoxylin + eosin). Arrows point out the tumors. (B) The occurrence of lung tumors in 5-mo-old mice plotted as percentage incidence. The asterisk indicates P < 0.05 compared with wild-type mice by Chi-squared test. We note that the tumor incidence of the checkpoint-defective group of mice as a whole is significantly increased relative to wild-type mice (P < 0.05 by Chi-squared test). (C) The average number of lung adenomas per mouse (±SEM). The asterisks indicate P < 0.05 compared with wild-type mice by Wilcoxon rank sum test.
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fig9: DMBA-induced tumor formation in checkpoint-defective mice. (A) Gross photograph of lung tumors of a DMBA-treated Rae1+/−/Bub3+/− mouse (left), and a section of a Rae1+/−/Bub3+/− lung tumor (right; 10×, hematoxylin + eosin). Arrows point out the tumors. (B) The occurrence of lung tumors in 5-mo-old mice plotted as percentage incidence. The asterisk indicates P < 0.05 compared with wild-type mice by Chi-squared test. We note that the tumor incidence of the checkpoint-defective group of mice as a whole is significantly increased relative to wild-type mice (P < 0.05 by Chi-squared test). (C) The average number of lung adenomas per mouse (±SEM). The asterisks indicate P < 0.05 compared with wild-type mice by Wilcoxon rank sum test.
Mentions: To determine whether single and double haplo-insufficient mice have increased susceptibility to carcinogen-induced tumorigenesis, we gave pups from Rae1+/− x Bub3+/− intercrosses a single application of 50 μl of a solution of 0.5% DMBA in acetone to the dorsal surface on post-natal day 5 (Serrano et al., 1996). 5 mo after DMBA treatment, the mice were killed and screened for tumor formation. Irrespective of the mouse genotype, tumors were exclusively detectable in the lungs (Fig. 9 A). In Rae1+/−, Bub3+/−, and Rae1+/−/Bub3+/− mice, the incidence of lung tumors was increased compared with their wild-type counterparts (Fig. 9 B), as was the average number of tumors per treated animal (Fig. 9 C). As controls, we examined 10 nontreated 5-mo-old mice per genotype for spontaneous tumors. No tumors were found in the wild-type, Rae1+/−, or Bub3+/− mice, whereas 1 of the 10 Rae1+/−/Bub3+/− mice had a lung tumor. Taken together, the above data indicate that mitotic checkpoint–defective mice are predisposed to chemical-induced lung tumorigenesis. We are monitoring over 50 mice per genotype (currently ranging in age from 2 to 7 mo) for possible development of spontaneous tumors as they age.

Bottom Line: Here we show that haplo-insufficiency of either Rae1 or Bub3 results in a similar phenotype involving mitotic checkpoint defects and chromosome missegregation.We also show that overexpression of Rae1 can correct for Rae1 haplo-insufficiency and, surprisingly, Bub3 haplo-insufficiency.Thus, our data demonstrate a novel function for Rae1 and characterize Rae1 and Bub3 as related proteins with essential, overlapping, and cooperating roles in the mitotic checkpoint.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN 55905, USA.

ABSTRACT
The WD-repeat proteins Rae1 and Bub3 show extensive sequence homology, indicative of functional similarity. However, previous studies have suggested that Rae1 is involved in the mRNA export pathway and Bub3 in the mitotic checkpoint. To determine the in vivo roles of Rae1 and Bub3 in mammals, we generated knockout mice that have these genes deleted individually or in combination. Here we show that haplo-insufficiency of either Rae1 or Bub3 results in a similar phenotype involving mitotic checkpoint defects and chromosome missegregation. We also show that overexpression of Rae1 can correct for Rae1 haplo-insufficiency and, surprisingly, Bub3 haplo-insufficiency. Rae1- and Bub3- mice are embryonic lethal, although cells from these mice did not have a detectable defect in nuclear export of mRNA. Unlike mice, compound haplo-insufficient Rae1/Bub3 mice are viable. However, cells from these mice exhibit much greater rates of premature sister chromatid separation and chromosome missegregation than single haplo-insufficient cells. Finally, we show that mice with mitotic checkpoint defects are more susceptible to dimethylbenzanthrene-induced tumorigenesis than wild-type mice. Thus, our data demonstrate a novel function for Rae1 and characterize Rae1 and Bub3 as related proteins with essential, overlapping, and cooperating roles in the mitotic checkpoint.

Show MeSH
Related in: MedlinePlus