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A novel mammalian, mitotic spindle-associated kinase is related to yeast and fly chromosome segregation regulators.

Gopalan G, Chan CS, Donovan PJ - J. Cell Biol. (1997)

Bottom Line: In cells recovering from nocodazole treatment and in taxol-treated mitotic cells, IAK1 is associated with microtubule organizing centers.We suggest that IAK1 is a new member of an emerging subfamily of the serine/threonine kinase superfamily.The members of this subfamily may be important regulators of chromosome segregation.

View Article: PubMed Central - PubMed

Affiliation: Cell Biology of Development and Differentiation Group, ABL Basic Research Program, National Cancer Institute, Frederick Cancer Research and Development Center, Frederick, Maryland 21702-1201, USA.

ABSTRACT
We describe a novel mammalian protein kinase related to two newly identified yeast and fly kinases-Ipl1 and aurora, respectively-mutations in which cause disruption of chromosome segregation. We have designated this kinase as Ipl1- and aurora-related kinase 1 (IAK1). IAK1 expression in mouse fibroblasts is tightly regulated temporally and spatially during the cell cycle. Transcripts first appear at G1/S boundary, are elevated at M-phase, and disappear rapidly after completion of mitosis. The protein levels and kinase activity of IAK1 are also cell cycle regulated with a peak at M-phase. IAK1 protein has a distinct subcellular and temporal pattern of localization. It is first identified on the centrosomes immediately after the duplicated centrosomes have separated. The protein remains on the centrosome and the centrosome-proximal part of the spindle throughout mitosis and is detected weakly on midbody microtubules at telophase and cytokinesis. In cells recovering from nocodazole treatment and in taxol-treated mitotic cells, IAK1 is associated with microtubule organizing centers. A wild-type and a mutant form of IAK1 cause mitotic spindle defects and lethality in ipl1 mutant yeast cells but not in wild-type cells, suggesting that IAK1 interferes with Ipl1p function in yeast. Taken together, these data strongly suggest that IAK1 may have an important role in centrosome and/ or spindle function during chromosome segregation in mammalian cells. We suggest that IAK1 is a new member of an emerging subfamily of the serine/threonine kinase superfamily. The members of this subfamily may be important regulators of chromosome segregation.

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Amino acid sequence alignment of IAK1 with those of  the STK1, Eg2, Ipl1, and aurora kinases. Identical amino acids  are shaded. Where amino acids are conserved in three or more of  these related kinases, shading is in black. Where amino acids are  conserved in only two members, shading is in gray. To maximize  alignment, gaps represented by dots were introduced. Amino  acid alignments were carried out using the University of Wisconsin Genetics Computer Group Program PILEUP.
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Figure 2: Amino acid sequence alignment of IAK1 with those of the STK1, Eg2, Ipl1, and aurora kinases. Identical amino acids are shaded. Where amino acids are conserved in three or more of these related kinases, shading is in black. Where amino acids are conserved in only two members, shading is in gray. To maximize alignment, gaps represented by dots were introduced. Amino acid alignments were carried out using the University of Wisconsin Genetics Computer Group Program PILEUP.

Mentions: Southern blot analysis of genomic DNA isolated from a variety of organisms indicates that IAK1 is highly evolutionarily conserved. We were able to detect hybridization of the IAK1 cDNA to genomic DNA isolated from human, chicken, Xenopus, and budding yeast (data not shown). Comparison of IAK1 sequence to other kinases in the database revealed that IAK1 is related to PKA and protein kinase C families. However, IAK1 is more closely related to Ipl1 and aurora, and they form a distinct subfamily of the serine/threonine kinases. The Ipl1 gene was originally isolated in studies designed to identify genes involved in chromosome disjunction in Saccharomyces cerevisiae (Chan and Botstein, 1993). Temperature-sensitive (ts) ipl1 mutant cells missegregate chromosomes severely and die at elevated temperatures. Subsequent isolation and characterization of the Ipl1 gene revealed that Ipl1 encodes a putative serine/threonine kinase and, furthermore, that abolition of Ipl1 gene function results in severe nondisjunction (Francisco et al., 1994). aurora was isolated in a search for mutations that affect the centrosome cycle in Drosophila. The loss of function of the kinase encoded by aurora results in failure of centrosome separation leading to the formation of monopolar spindles (Glover et al., 1995). Fig. 2 shows a comparison of the amino acid sequence between IAK1, Ipl1p, and aurora and two other related kinases. The sequence homology between these kinases extends beyond the highly conserved COOH-terminal catalytic domain. Ipl1p shows an overall identity of 47% over the entire protein and 49% identity in the kinase domain to IAK1. Similarly, aurora is 56% identical to IAK1 over the entire protein and 58% identical in the kinase domain. IAK1 also shows a high degree of homology (74%) to a newly described cell cycle–regulated kinase of unknown function, STK1, identified from mouse testis (Niwa et al., 1996). It also shares 75% homology with Eg2, a frog homologue also of unknown function, whose sequence data are available from GenBank/EMBL/DDBJ under accession number Z17207 (Fig. 2).


A novel mammalian, mitotic spindle-associated kinase is related to yeast and fly chromosome segregation regulators.

Gopalan G, Chan CS, Donovan PJ - J. Cell Biol. (1997)

Amino acid sequence alignment of IAK1 with those of  the STK1, Eg2, Ipl1, and aurora kinases. Identical amino acids  are shaded. Where amino acids are conserved in three or more of  these related kinases, shading is in black. Where amino acids are  conserved in only two members, shading is in gray. To maximize  alignment, gaps represented by dots were introduced. Amino  acid alignments were carried out using the University of Wisconsin Genetics Computer Group Program PILEUP.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2141637&req=5

Figure 2: Amino acid sequence alignment of IAK1 with those of the STK1, Eg2, Ipl1, and aurora kinases. Identical amino acids are shaded. Where amino acids are conserved in three or more of these related kinases, shading is in black. Where amino acids are conserved in only two members, shading is in gray. To maximize alignment, gaps represented by dots were introduced. Amino acid alignments were carried out using the University of Wisconsin Genetics Computer Group Program PILEUP.
Mentions: Southern blot analysis of genomic DNA isolated from a variety of organisms indicates that IAK1 is highly evolutionarily conserved. We were able to detect hybridization of the IAK1 cDNA to genomic DNA isolated from human, chicken, Xenopus, and budding yeast (data not shown). Comparison of IAK1 sequence to other kinases in the database revealed that IAK1 is related to PKA and protein kinase C families. However, IAK1 is more closely related to Ipl1 and aurora, and they form a distinct subfamily of the serine/threonine kinases. The Ipl1 gene was originally isolated in studies designed to identify genes involved in chromosome disjunction in Saccharomyces cerevisiae (Chan and Botstein, 1993). Temperature-sensitive (ts) ipl1 mutant cells missegregate chromosomes severely and die at elevated temperatures. Subsequent isolation and characterization of the Ipl1 gene revealed that Ipl1 encodes a putative serine/threonine kinase and, furthermore, that abolition of Ipl1 gene function results in severe nondisjunction (Francisco et al., 1994). aurora was isolated in a search for mutations that affect the centrosome cycle in Drosophila. The loss of function of the kinase encoded by aurora results in failure of centrosome separation leading to the formation of monopolar spindles (Glover et al., 1995). Fig. 2 shows a comparison of the amino acid sequence between IAK1, Ipl1p, and aurora and two other related kinases. The sequence homology between these kinases extends beyond the highly conserved COOH-terminal catalytic domain. Ipl1p shows an overall identity of 47% over the entire protein and 49% identity in the kinase domain to IAK1. Similarly, aurora is 56% identical to IAK1 over the entire protein and 58% identical in the kinase domain. IAK1 also shows a high degree of homology (74%) to a newly described cell cycle–regulated kinase of unknown function, STK1, identified from mouse testis (Niwa et al., 1996). It also shares 75% homology with Eg2, a frog homologue also of unknown function, whose sequence data are available from GenBank/EMBL/DDBJ under accession number Z17207 (Fig. 2).

Bottom Line: In cells recovering from nocodazole treatment and in taxol-treated mitotic cells, IAK1 is associated with microtubule organizing centers.We suggest that IAK1 is a new member of an emerging subfamily of the serine/threonine kinase superfamily.The members of this subfamily may be important regulators of chromosome segregation.

View Article: PubMed Central - PubMed

Affiliation: Cell Biology of Development and Differentiation Group, ABL Basic Research Program, National Cancer Institute, Frederick Cancer Research and Development Center, Frederick, Maryland 21702-1201, USA.

ABSTRACT
We describe a novel mammalian protein kinase related to two newly identified yeast and fly kinases-Ipl1 and aurora, respectively-mutations in which cause disruption of chromosome segregation. We have designated this kinase as Ipl1- and aurora-related kinase 1 (IAK1). IAK1 expression in mouse fibroblasts is tightly regulated temporally and spatially during the cell cycle. Transcripts first appear at G1/S boundary, are elevated at M-phase, and disappear rapidly after completion of mitosis. The protein levels and kinase activity of IAK1 are also cell cycle regulated with a peak at M-phase. IAK1 protein has a distinct subcellular and temporal pattern of localization. It is first identified on the centrosomes immediately after the duplicated centrosomes have separated. The protein remains on the centrosome and the centrosome-proximal part of the spindle throughout mitosis and is detected weakly on midbody microtubules at telophase and cytokinesis. In cells recovering from nocodazole treatment and in taxol-treated mitotic cells, IAK1 is associated with microtubule organizing centers. A wild-type and a mutant form of IAK1 cause mitotic spindle defects and lethality in ipl1 mutant yeast cells but not in wild-type cells, suggesting that IAK1 interferes with Ipl1p function in yeast. Taken together, these data strongly suggest that IAK1 may have an important role in centrosome and/ or spindle function during chromosome segregation in mammalian cells. We suggest that IAK1 is a new member of an emerging subfamily of the serine/threonine kinase superfamily. The members of this subfamily may be important regulators of chromosome segregation.

Show MeSH