Biomedical subjects

Nicholas J Quintyne

Publications and source records attributed to Nicholas J Quintyne.

4 recordsLinked to original sources

PubMed2006

A microtubule-binding domain in dynactin increases dynein processivity by skating along microtubules.

Microtubule-associated proteins (MAPs) use particular microtubule-binding domains that allow them to interact with microtubules in a manner specific to their individual cellular functions. Here, we have identified a highly basic microtubule-binding domain in the p150 subunit of dynactin that is only present in the dynactin members of the CAP-Gly family of proteins. Using single-particle microtubule-binding assays, we found that the basic domain of dynactin moves progressively along microtubules in the absence of molecular motors - a process we term 'skating'. In contrast, the previously described CAP-Gly domain of dynactin remains firmly attached to a single point on microtubules. Further analyses showed that microtubule skating is a form of one-dimensional diffusion along the microtubule. To determine the cellular function of the skating phenomenon, dynein and the dynactin microtubule-binding domains were examined in single-molecule motility assays. We found that the basic domain increased dynein processivity fourfold whereas the CAP-Gly domain inhibited dynein motility. Our data show that the ability of the basic domain of dynactin to skate along microtubules is used by dynein to maintain longer interactions for each encounter with microtubules.

Amino Acid Sequence↗

PubMed2005

Spindle multipolarity is prevented by centrosomal clustering.

Most tumor cells are characterized by increased genomic instability and chromosome segregational defects, often associated with hyperamplification of the centrosome and the formation of multipolar spindles. However, extra centrosomes do not always lead to multipolarity. Here, we describe a process of centrosomal clustering that prevented the formation of multipolar spindles in noncancer cells. Noncancer cells needed to overcome this clustering mechanism to allow multipolar spindles to form at a high frequency. The microtubule motor cytoplasmic dynein was a critical part of this coalescing machinery, and in some tumor cells overexpression of the spindle protein NuMA interfered with dynein localization, promoting multipolarity.

Antigens, Nuclear↗

PubMed2003

Analysis of the dynein-dynactin interaction in vitro and in vivo.

Cytoplasmic dynein and dynactin are megadalton-sized multisubunit molecules that function together as a cytoskeletal motor. In the present study, we explore the mechanism of dynein-dynactin binding in vitro and then extend our findings to an in vivo context. Solution binding assays were used to define binding domains in the dynein intermediate chain (IC) and dynactin p150Glued subunit. Transient overexpression of a series of fragments of the dynein IC was used to determine the importance of this subunit for dynein function in mammalian tissue culture cells. Our results suggest that a functional dynein-dynactin interaction is required for proper microtubule organization and for the transport and localization of centrosomal components and endomembrane compartments. The dynein IC fragments have different effects on endomembrane localization, suggesting that different endomembranes may bind dynein via distinct mechanisms.

Animals↗

PubMed2002

Distinct cell cycle-dependent roles for dynactin and dynein at centrosomes.

Centrosomal dynactin is required for normal microtubule anchoring and/or focusing independently of dynein. Dynactin is present at centrosomes throughout interphase, but dynein accumulates only during S and G2 phases. Blocking dynein-based motility prevents recruitment of dynactin and dynein to centrosomes and destabilizes both centrosomes and the microtubule array, interfering with cell cycle progression during mitosis. Destabilization of the centrosomal pool of dynactin does not inhibit dynein-based motility or dynein recruitment to centrosomes, but instead causes abnormal G1 centriole separation and delayed entry into S phase. The correct balance of centrosome-associated dynactin subunits is apparently important for satisfaction of the cell cycle mechanism that monitors centrosome integrity before centrosome duplication and ultimately governs the G1 to S transition. Our results suggest that, in addition to functioning as a microtubule anchor, dynactin contributes to the recruitment of important cell cycle regulators to centrosomes.

Animals↗