Anjon Audhya et al. (2005) International Worm Meeting "The Scd6p family protein CAR-1 is a component of a complex of RNA-binding proteins required for cytokinesis in C. elegans"

Ian MacLeod, Anjon Audhya, Francie Hyndman, Amy Maddox, Karen Oegema

[International Worm Meeting, 2005]

Cytokinesis completes cell division by partitioning the intracellular constituents of one cell to form two topologically distinct daughter cells. Here we describe the characterization of CAR-1, a predicted RNA binding protein whose depletion results in a specific defect in cytokinesis. Consistent with a role in RNA metabolism, CAR-1 localizes to germline-specific RNA-containing P-granules and co-purifies with the essential RNA helicase CGH-1, which controls its localization. The atypical Sm domain of CAR-1, which is predicted to mediate an association with RNA, is dispensable for CAR-1 localization but critical for its function. The failure of cytokinesis in CAR-1 depleted embryos likely results from a pronounced defect in the structure of the anaphase spindle, which normally interacts with the cortex to promote the completion of cytokinesis. In CAR-1 depleted embryos, inter-zonal microtubule bundles that recruit Aurora B kinase and the kinesin ZEN-4 fail to form. Depletion of CGH-1 results in sterility, but partially depleted worms produce embryos that exhibit a nearly identical phenotype to that resulting from depletion of CAR-1. Cumulatively, these results suggest that CAR-1 and CGH-1 function together to regulate RNAs important for anaphase spindle structure and point to a connection between RNA metabolism and cytokinesis.

Paul Maddox et al. (2007) International Worm Meeting "Functional genomics identifies a Myb domain-containing protein family required for assembly of CENP-A chromatin."

Joost Monen, Arshad Desai, Francie Hyndman, Karen Oegema, Paul Maddox

[International Worm Meeting, 2007]

Nucleosomes containing the centromere-specific histone H3 variant centromere protein A (CENP-A) create the chromatin foundation for kinetochore assembly. To understand the mechanisms that selectively target CENP-A to centromeres, we took a functional genomics approach in the nematode Caenorhabditis elegans, in which failure to load CENP-A results in a signature kinetochore-null (KNL) phenotype. We identified a single protein, KNL-2, that is specifically required for CENP-A incorporation into chromatin. KNL-2 and CENP-A localize to centromeres throughout the cell cycle in an interdependent manner and coordinately direct chromosome condensation, kinetochore assembly, and chromosome segregation. The isolation of KNL-2-associated chromatin coenriched CENP-A, indicating their close proximity on DNA. KNL-2 defines a new conserved family of Myb DNA-binding domain-containing proteins. The human homologue of KNL-2 is also specifically required for CENP-A loading and kinetochore assembly but is only transiently present at centromeres after mitotic exit. These results implicate a new protein class in the assembly of centromeric chromatin and suggest that holocentric and monocentric chromosomes share a common mechanism for CENP-A loading.