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Dictyostelium IQGAP-related protein specifically involved in the completion of cytokinesis.

Adachi H, Takahashi Y, Hasebe T, Shirouzu M, Yokoyama S, Sutoh K - J. Cell Biol. (1997)

Bottom Line: These results indicate that the GAPA protein is specifically involved in the completion of cytokinesis.Recently, it was reported that IQGAPs are putative effectors for Rac and CDC42, members of the Rho family of GTPases, and participate in reorganization of the actin cytoskeleton.Thus, it is possible that Dictyostelium GAPA participates in the severing of the midbody by regulating the actin cytoskeleton through an interaction with a member of small GTPases.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153. f37771@m-unix.cc.u-tokyo.ac.jp

ABSTRACT
The gapA gene encoding a novel RasGTPase-activating protein (RasGAP)-related protein was found to be disrupted in a cytokinesis mutant of Dictyostelium that grows as giant and multinucleate cells in a dish culture. The predicted sequence of the GAPA protein showed considerable homology to those of Gap1/Sar1 from fission yeast and the COOH-terminal half of mammalian IQGAPs, the similarity extending beyond the RasGAP-related domain. In suspension culture, gapA- cells showed normal growth in terms of the increase in cell mass, but cytokinesis inefficiently occurred to produce spherical giant cells. Time-lapse recording of the dynamics of cell division in a dish culture revealed that, in the case of gapA- cells, cytokinesis was very frequently reversed at the step in which the midbody connecting the daughter cells should be severed. Earlier steps of cytokinesis in the gapA- cells seemed to be normal, since myosin II was accumulated at the cleavage furrow. Upon starvation, gapA- cells developed and formed fruiting bodies with viable spores, like the wild-type cells. These results indicate that the GAPA protein is specifically involved in the completion of cytokinesis. Recently, it was reported that IQGAPs are putative effectors for Rac and CDC42, members of the Rho family of GTPases, and participate in reorganization of the actin cytoskeleton. Thus, it is possible that Dictyostelium GAPA participates in the severing of the midbody by regulating the actin cytoskeleton through an interaction with a member of small GTPases.

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Related in: MedlinePlus

DNA sequence of the Dictyostelium gapA gene and the  deduced amino acid sequence of the GAPA protein. The coding  DNA sequences (exons) are indicated by capital letters, and the  5′ and 3′ flanking sequences as well as introns are shown in lowercase letters. (Boxed region) RasGAP-related domain (GRD).  In cytokinesis mutant D42-2, the tag was inserted into the underlined GATC sequence in the fourth exon. These sequence data  are available from EMBL/GenBank/DDBJ under accession number D88027.
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Figure 4: DNA sequence of the Dictyostelium gapA gene and the deduced amino acid sequence of the GAPA protein. The coding DNA sequences (exons) are indicated by capital letters, and the 5′ and 3′ flanking sequences as well as introns are shown in lowercase letters. (Boxed region) RasGAP-related domain (GRD). In cytokinesis mutant D42-2, the tag was inserted into the underlined GATC sequence in the fourth exon. These sequence data are available from EMBL/GenBank/DDBJ under accession number D88027.

Mentions: DNA sequencing of the HindIII–ClaI fragment revealed an open reading frame interrupted by three putative introns with typical features of Dictyostelium introns (Figs. 1 and 4). The intron–exon boundaries were confirmed by sequence analysis of cDNA clones prepared from the vegetative mRNA (data not shown). It was found that the tag was inserted into the fourth exon of the gene in the D42-2 DNA (Figs. 1 and 4), and that the open reading frame is 2,580 bp in length and codes for a protein of 860 amino acids (molecular mass = 98.8 kD).


Dictyostelium IQGAP-related protein specifically involved in the completion of cytokinesis.

Adachi H, Takahashi Y, Hasebe T, Shirouzu M, Yokoyama S, Sutoh K - J. Cell Biol. (1997)

DNA sequence of the Dictyostelium gapA gene and the  deduced amino acid sequence of the GAPA protein. The coding  DNA sequences (exons) are indicated by capital letters, and the  5′ and 3′ flanking sequences as well as introns are shown in lowercase letters. (Boxed region) RasGAP-related domain (GRD).  In cytokinesis mutant D42-2, the tag was inserted into the underlined GATC sequence in the fourth exon. These sequence data  are available from EMBL/GenBank/DDBJ under accession number D88027.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2139833&req=5

Figure 4: DNA sequence of the Dictyostelium gapA gene and the deduced amino acid sequence of the GAPA protein. The coding DNA sequences (exons) are indicated by capital letters, and the 5′ and 3′ flanking sequences as well as introns are shown in lowercase letters. (Boxed region) RasGAP-related domain (GRD). In cytokinesis mutant D42-2, the tag was inserted into the underlined GATC sequence in the fourth exon. These sequence data are available from EMBL/GenBank/DDBJ under accession number D88027.
Mentions: DNA sequencing of the HindIII–ClaI fragment revealed an open reading frame interrupted by three putative introns with typical features of Dictyostelium introns (Figs. 1 and 4). The intron–exon boundaries were confirmed by sequence analysis of cDNA clones prepared from the vegetative mRNA (data not shown). It was found that the tag was inserted into the fourth exon of the gene in the D42-2 DNA (Figs. 1 and 4), and that the open reading frame is 2,580 bp in length and codes for a protein of 860 amino acids (molecular mass = 98.8 kD).

Bottom Line: These results indicate that the GAPA protein is specifically involved in the completion of cytokinesis.Recently, it was reported that IQGAPs are putative effectors for Rac and CDC42, members of the Rho family of GTPases, and participate in reorganization of the actin cytoskeleton.Thus, it is possible that Dictyostelium GAPA participates in the severing of the midbody by regulating the actin cytoskeleton through an interaction with a member of small GTPases.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153. f37771@m-unix.cc.u-tokyo.ac.jp

ABSTRACT
The gapA gene encoding a novel RasGTPase-activating protein (RasGAP)-related protein was found to be disrupted in a cytokinesis mutant of Dictyostelium that grows as giant and multinucleate cells in a dish culture. The predicted sequence of the GAPA protein showed considerable homology to those of Gap1/Sar1 from fission yeast and the COOH-terminal half of mammalian IQGAPs, the similarity extending beyond the RasGAP-related domain. In suspension culture, gapA- cells showed normal growth in terms of the increase in cell mass, but cytokinesis inefficiently occurred to produce spherical giant cells. Time-lapse recording of the dynamics of cell division in a dish culture revealed that, in the case of gapA- cells, cytokinesis was very frequently reversed at the step in which the midbody connecting the daughter cells should be severed. Earlier steps of cytokinesis in the gapA- cells seemed to be normal, since myosin II was accumulated at the cleavage furrow. Upon starvation, gapA- cells developed and formed fruiting bodies with viable spores, like the wild-type cells. These results indicate that the GAPA protein is specifically involved in the completion of cytokinesis. Recently, it was reported that IQGAPs are putative effectors for Rac and CDC42, members of the Rho family of GTPases, and participate in reorganization of the actin cytoskeleton. Thus, it is possible that Dictyostelium GAPA participates in the severing of the midbody by regulating the actin cytoskeleton through an interaction with a member of small GTPases.

Show MeSH
Related in: MedlinePlus