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Australin: a chromosomal passenger protein required specifically for Drosophila melanogaster male meiosis.

Gao S, Giansanti MG, Buttrick GJ, Ramasubramanyan S, Auton A, Gatti M, Wakefield JG - J. Cell Biol. (2008)

Bottom Line: Here we find that Drosophila melanogaster encodes two Borealin paralogues, Borealin-related (Borr) and Australin (Aust).We analyzed aust mutant spermatocytes to assess the effects of fully inactivating the Aust-dependent functions of the CPC.Our results indicate that Aust is required for sister chromatid cohesion, recruitment of the CPC to kinetochores, and chromosome alignment and segregation but not for meiotic histone phosphorylation or spindle formation.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, University of Oxford, OX1 3PS Oxford, England, UK.

ABSTRACT
The chromosomal passenger complex (CPC), which is composed of conserved proteins aurora B, inner centromere protein (INCENP), survivin, and Borealin/DASRA, localizes to chromatin, kinetochores, microtubules, and the cell cortex in a cell cycle-dependent manner. The CPC is required for multiple aspects of cell division. Here we find that Drosophila melanogaster encodes two Borealin paralogues, Borealin-related (Borr) and Australin (Aust). Although Borr is a passenger in all mitotic tissues studied, it is specifically replaced by Aust for the two male meiotic divisions. We analyzed aust mutant spermatocytes to assess the effects of fully inactivating the Aust-dependent functions of the CPC. Our results indicate that Aust is required for sister chromatid cohesion, recruitment of the CPC to kinetochores, and chromosome alignment and segregation but not for meiotic histone phosphorylation or spindle formation. Furthermore, we show that the CPC is required earlier in cytokinesis than previously thought; cells lacking Aust do not initiate central spindle formation, accumulate anillin or actin at the cell equator, or undergo equatorial constriction.

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CG17009 encodes aust, a paralogue of borr. (A) RT-PCR of aust candidate genes using cDNA from wild-type or aust testes. (B) Representation of CG17009 and its neighboring gene CG4454 (borr). Regions corresponding to the proximal and distal exons of borr show homology with the two CG17009 exons (broken lines). Sequencing from two independent aust alleles identified point mutations in CG17009. (C) Alignment of Aust and Borr protein sequences using ClustalW (Thompson et al., 1994). Arrows denote amino acids. Black asterisks, conserved residues; red asterisks, point mutations present in the aust alleles. (D) Phylogenetic tree of aust and borr for Drosophila species using the XP_309424 gene from Anopheles gambiae as the outgroup. Significance was assessed via bootstrapping with 1,000 replicates. Bootstrap values are shown.
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fig2: CG17009 encodes aust, a paralogue of borr. (A) RT-PCR of aust candidate genes using cDNA from wild-type or aust testes. (B) Representation of CG17009 and its neighboring gene CG4454 (borr). Regions corresponding to the proximal and distal exons of borr show homology with the two CG17009 exons (broken lines). Sequencing from two independent aust alleles identified point mutations in CG17009. (C) Alignment of Aust and Borr protein sequences using ClustalW (Thompson et al., 1994). Arrows denote amino acids. Black asterisks, conserved residues; red asterisks, point mutations present in the aust alleles. (D) Phylogenetic tree of aust and borr for Drosophila species using the XP_309424 gene from Anopheles gambiae as the outgroup. Significance was assessed via bootstrapping with 1,000 replicates. Bootstrap values are shown.

Mentions: Using complementation analysis to a series of deficiency chromosomes and individual mutants, we mapped the aust locus to one of six genes (see Materials and methods and Fig. S1). To define which of these corresponded to the aust locus, we both assessed the expression of each gene in wild-type or aust1 testes using RT-PCR and sequenced each gene from genomic DNA extracted from wild-type or aust1 flies. For five of the six genes, the expression and the DNA sequence were identical between wild-type and aust1 flies (Fig. 2 A). However, aust1 testes failed to express CG17009, and sequencing of the gene from aust1 individuals identified a point mutation in the splice donor site at the exon–intron boundary (Fig. 2, A and B). Sequencing of genomic DNA isolated from a second aust allele identified during the course of our studies, aust2, also identified a single point mutation in the CG17009-coding region, resulting in an Ile–Ser amino acid substitution toward the C terminus of the protein (Fig. 2 B and not depicted). Together, these results confirm CG17009 as the aust locus.


Australin: a chromosomal passenger protein required specifically for Drosophila melanogaster male meiosis.

Gao S, Giansanti MG, Buttrick GJ, Ramasubramanyan S, Auton A, Gatti M, Wakefield JG - J. Cell Biol. (2008)

CG17009 encodes aust, a paralogue of borr. (A) RT-PCR of aust candidate genes using cDNA from wild-type or aust testes. (B) Representation of CG17009 and its neighboring gene CG4454 (borr). Regions corresponding to the proximal and distal exons of borr show homology with the two CG17009 exons (broken lines). Sequencing from two independent aust alleles identified point mutations in CG17009. (C) Alignment of Aust and Borr protein sequences using ClustalW (Thompson et al., 1994). Arrows denote amino acids. Black asterisks, conserved residues; red asterisks, point mutations present in the aust alleles. (D) Phylogenetic tree of aust and borr for Drosophila species using the XP_309424 gene from Anopheles gambiae as the outgroup. Significance was assessed via bootstrapping with 1,000 replicates. Bootstrap values are shown.
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fig2: CG17009 encodes aust, a paralogue of borr. (A) RT-PCR of aust candidate genes using cDNA from wild-type or aust testes. (B) Representation of CG17009 and its neighboring gene CG4454 (borr). Regions corresponding to the proximal and distal exons of borr show homology with the two CG17009 exons (broken lines). Sequencing from two independent aust alleles identified point mutations in CG17009. (C) Alignment of Aust and Borr protein sequences using ClustalW (Thompson et al., 1994). Arrows denote amino acids. Black asterisks, conserved residues; red asterisks, point mutations present in the aust alleles. (D) Phylogenetic tree of aust and borr for Drosophila species using the XP_309424 gene from Anopheles gambiae as the outgroup. Significance was assessed via bootstrapping with 1,000 replicates. Bootstrap values are shown.
Mentions: Using complementation analysis to a series of deficiency chromosomes and individual mutants, we mapped the aust locus to one of six genes (see Materials and methods and Fig. S1). To define which of these corresponded to the aust locus, we both assessed the expression of each gene in wild-type or aust1 testes using RT-PCR and sequenced each gene from genomic DNA extracted from wild-type or aust1 flies. For five of the six genes, the expression and the DNA sequence were identical between wild-type and aust1 flies (Fig. 2 A). However, aust1 testes failed to express CG17009, and sequencing of the gene from aust1 individuals identified a point mutation in the splice donor site at the exon–intron boundary (Fig. 2, A and B). Sequencing of genomic DNA isolated from a second aust allele identified during the course of our studies, aust2, also identified a single point mutation in the CG17009-coding region, resulting in an Ile–Ser amino acid substitution toward the C terminus of the protein (Fig. 2 B and not depicted). Together, these results confirm CG17009 as the aust locus.

Bottom Line: Here we find that Drosophila melanogaster encodes two Borealin paralogues, Borealin-related (Borr) and Australin (Aust).We analyzed aust mutant spermatocytes to assess the effects of fully inactivating the Aust-dependent functions of the CPC.Our results indicate that Aust is required for sister chromatid cohesion, recruitment of the CPC to kinetochores, and chromosome alignment and segregation but not for meiotic histone phosphorylation or spindle formation.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, University of Oxford, OX1 3PS Oxford, England, UK.

ABSTRACT
The chromosomal passenger complex (CPC), which is composed of conserved proteins aurora B, inner centromere protein (INCENP), survivin, and Borealin/DASRA, localizes to chromatin, kinetochores, microtubules, and the cell cortex in a cell cycle-dependent manner. The CPC is required for multiple aspects of cell division. Here we find that Drosophila melanogaster encodes two Borealin paralogues, Borealin-related (Borr) and Australin (Aust). Although Borr is a passenger in all mitotic tissues studied, it is specifically replaced by Aust for the two male meiotic divisions. We analyzed aust mutant spermatocytes to assess the effects of fully inactivating the Aust-dependent functions of the CPC. Our results indicate that Aust is required for sister chromatid cohesion, recruitment of the CPC to kinetochores, and chromosome alignment and segregation but not for meiotic histone phosphorylation or spindle formation. Furthermore, we show that the CPC is required earlier in cytokinesis than previously thought; cells lacking Aust do not initiate central spindle formation, accumulate anillin or actin at the cell equator, or undergo equatorial constriction.

Show MeSH
Related in: MedlinePlus