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Cortical Num1p interacts with the dynein intermediate chain Pac11p and cytoplasmic microtubules in budding yeast.

Farkasovsky M, Küntzel H - J. Cell Biol. (2001)

Bottom Line: The bud tip location of Num1p depends on Bni1p but does not require Kar9p, Dyn1p, or cMTs, whereas cMT contacts with polar Num1p dots are reduced in cells lacking Dyn1p.Num1p also forms a complex with Bni1p and Kar9p, although Num1p is not required for Bni1p- and Kar9p-dependent nuclear migration to the bud neck in preanaphase cells.In addition, Num1p may transiently cooperate with an associated Bni1p-Kar9p complex at the bud tip of early anaphase cells.

View Article: PubMed Central - PubMed

Affiliation: Max-Planck Institute for Experimental Medicine, D-37075 Göttingen, Germany.

ABSTRACT
Num1p, a cortical 313-kD protein, controls cytoplasmic microtubule (cMT) functions and nuclear migration through the bud neck in anaphase cells. A green fluorescent protein (GFP)-Num1p fusion protein localizes at the bud tip and the distal mother pole of living cells, apparently forming cMT capture sites at late anaphase. In addition, galactose-induced GFP-Num1p is seen at the bud neck and in lateral regions of the mother cortex. The bud tip location of Num1p depends on Bni1p but does not require Kar9p, Dyn1p, or cMTs, whereas cMT contacts with polar Num1p dots are reduced in cells lacking Dyn1p. Num1p associates with the dynein intermediate chain Pac11p in the presence of Dyn1p, and with the alpha-tubulin Tub3p, as shown by coimmune precipitation of tagged proteins. Num1p also forms a complex with Bni1p and Kar9p, although Num1p is not required for Bni1p- and Kar9p-dependent nuclear migration to the bud neck in preanaphase cells. Our data suggest that Num1p controls nuclear migration during late anaphase by forming dynein-interacting cortical cMT capture sites at both cellular poles. In addition, Num1p may transiently cooperate with an associated Bni1p-Kar9p complex at the bud tip of early anaphase cells.

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Quantification of cMT–cortex interactions in WT (FMY519) and dyn1Δ (FMY872) anaphase cells expressing galactose-induced GFP-Num1p. The percentage of cells with indicated cMT–cortex contacts was determined for early anaphase cells (short spindle entering the bud), mid anaphase cells (partially elongated spindle spanning the neck), and late anaphase cells (fully elongated spindle). (n) Number of cells analyzed. For details see legend to Fig. 2.
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Figure 4: Quantification of cMT–cortex interactions in WT (FMY519) and dyn1Δ (FMY872) anaphase cells expressing galactose-induced GFP-Num1p. The percentage of cells with indicated cMT–cortex contacts was determined for early anaphase cells (short spindle entering the bud), mid anaphase cells (partially elongated spindle spanning the neck), and late anaphase cells (fully elongated spindle). (n) Number of cells analyzed. For details see legend to Fig. 2.

Mentions: The interactions of cMTs with galactose-induced cortical Num1p dots at the poles of anaphase cells (Fig. 2C and Fig. D) are summarized in Fig. 4. A contact of cMTs to both polar Num1p dots is not observed in early anaphase cells, but is seen in 9% of mid anaphase and in 64% of late anaphase cells (Fig. 4, column A). cMTs appear to contact Num1p at the bud tip but not at the opposite mother pole in 23% of early anaphase, 65% of mid anaphase, and 28% of late anaphase cells (Fig. 4, column B). cMTs contacting lateral regions of the bud and mother cortex, instead of touching the cellular poles, are seen in 72% of early anaphase, 26% of mid anaphase, and 8% of late anaphase cells (Fig. 4, column C).


Cortical Num1p interacts with the dynein intermediate chain Pac11p and cytoplasmic microtubules in budding yeast.

Farkasovsky M, Küntzel H - J. Cell Biol. (2001)

Quantification of cMT–cortex interactions in WT (FMY519) and dyn1Δ (FMY872) anaphase cells expressing galactose-induced GFP-Num1p. The percentage of cells with indicated cMT–cortex contacts was determined for early anaphase cells (short spindle entering the bud), mid anaphase cells (partially elongated spindle spanning the neck), and late anaphase cells (fully elongated spindle). (n) Number of cells analyzed. For details see legend to Fig. 2.
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Related In: Results  -  Collection

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Figure 4: Quantification of cMT–cortex interactions in WT (FMY519) and dyn1Δ (FMY872) anaphase cells expressing galactose-induced GFP-Num1p. The percentage of cells with indicated cMT–cortex contacts was determined for early anaphase cells (short spindle entering the bud), mid anaphase cells (partially elongated spindle spanning the neck), and late anaphase cells (fully elongated spindle). (n) Number of cells analyzed. For details see legend to Fig. 2.
Mentions: The interactions of cMTs with galactose-induced cortical Num1p dots at the poles of anaphase cells (Fig. 2C and Fig. D) are summarized in Fig. 4. A contact of cMTs to both polar Num1p dots is not observed in early anaphase cells, but is seen in 9% of mid anaphase and in 64% of late anaphase cells (Fig. 4, column A). cMTs appear to contact Num1p at the bud tip but not at the opposite mother pole in 23% of early anaphase, 65% of mid anaphase, and 28% of late anaphase cells (Fig. 4, column B). cMTs contacting lateral regions of the bud and mother cortex, instead of touching the cellular poles, are seen in 72% of early anaphase, 26% of mid anaphase, and 8% of late anaphase cells (Fig. 4, column C).

Bottom Line: The bud tip location of Num1p depends on Bni1p but does not require Kar9p, Dyn1p, or cMTs, whereas cMT contacts with polar Num1p dots are reduced in cells lacking Dyn1p.Num1p also forms a complex with Bni1p and Kar9p, although Num1p is not required for Bni1p- and Kar9p-dependent nuclear migration to the bud neck in preanaphase cells.In addition, Num1p may transiently cooperate with an associated Bni1p-Kar9p complex at the bud tip of early anaphase cells.

View Article: PubMed Central - PubMed

Affiliation: Max-Planck Institute for Experimental Medicine, D-37075 Göttingen, Germany.

ABSTRACT
Num1p, a cortical 313-kD protein, controls cytoplasmic microtubule (cMT) functions and nuclear migration through the bud neck in anaphase cells. A green fluorescent protein (GFP)-Num1p fusion protein localizes at the bud tip and the distal mother pole of living cells, apparently forming cMT capture sites at late anaphase. In addition, galactose-induced GFP-Num1p is seen at the bud neck and in lateral regions of the mother cortex. The bud tip location of Num1p depends on Bni1p but does not require Kar9p, Dyn1p, or cMTs, whereas cMT contacts with polar Num1p dots are reduced in cells lacking Dyn1p. Num1p associates with the dynein intermediate chain Pac11p in the presence of Dyn1p, and with the alpha-tubulin Tub3p, as shown by coimmune precipitation of tagged proteins. Num1p also forms a complex with Bni1p and Kar9p, although Num1p is not required for Bni1p- and Kar9p-dependent nuclear migration to the bud neck in preanaphase cells. Our data suggest that Num1p controls nuclear migration during late anaphase by forming dynein-interacting cortical cMT capture sites at both cellular poles. In addition, Num1p may transiently cooperate with an associated Bni1p-Kar9p complex at the bud tip of early anaphase cells.

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