Hutterer A et al. (2006) Dev Cell "Mitotic activation of the kinase Aurora-A requires its binding partner Bora."

Zigman M, Hutterer A, Schleiffer A, Wirtz-Peitz F, Knoblich JA, Berdnik D

[Dev Cell, 2006]

The protein kinase Aurora-A is required for centrosome maturation, spindle assembly, and asymmetric protein localization during mitosis. Here, we describe the identification of Bora, a conserved protein that is required for the activation of Aurora-A at the onset of mitosis. In the Drosophila peripheral nervous system, bora mutants have defects during asymmetric cell division identical to those observed in aurora-A. Furthermore, overexpression of bora can rescue defects caused by mutations in aurora-A. Bora is conserved in vertebrates, and both Drosophila and human Bora can bind to Aurora-A and activate the kinase in vitro. In interphase cells, Bora is a nuclear protein, but upon entry into mitosis, Bora is excluded from the nucleus and translocates into the cytoplasm in a Cdc2-dependent manner. We propose a model in which activation of Cdc2 initiates the release of Bora into the cytoplasm where it can bind and activate Aurora-A.

Kreutzer MA et al. (1995) J Cell Sci "Caenorhabditis elegans cyclin A- and B-type genes: a cyclin A multigene family, an ancestral cyclin B3 and differential germline expression."

De Silva-Udawatta MN, Kreutzer MA, Knoblich JA, Richards JP, Lehner CF, Temenak JJ, Bennett KL

[J Cell Sci, 1995]

We have cloned cDNAs for Caenorhabditis elegans cyclins A1, B and B3. While cyclins A1 and B are most closely related to either A- or B-type cyclins of other species, cyclin B3 is less related to these cyclins. However, this cyclin is most similar to the recently identified chicken cyclin B3. Our identification of a Caenorhabditis homolog demonstrates that cyclin B3 has been conserved in evolution. Cyclin A1 is a member of an A-type multigene family; however the cyclin A1 cDNA only recognizes a single band on northern blots. A single-sized RNA is also observed for the cyclin B3 cDNA. In contrast, three different transcripts are observed for the cyclin B cDNA. Based on our analyses using RNAs from germline-defective mutants and from populations enriched for males, one cyclin B transcript is specific to the paternal germline. The two other cyclin B transcripts, as well as the cyclin A1 and cyclin B3 transcripts, are most abundant in the maternal germline and are only present at low levels in other tissues. Moreover, the 3' untranslated regions of each Caenorhabditis cyclin cDNA possess several copies of potential translational control elements shown in Xenopus and Drosophila maternal cyclin mRNAs to function during oogenesis and early embryogenesis.

Zhang H et al. (2008) Mol Biol Cell "RAB-11 permissively regulates spindle alignment by modulating metaphase microtubule dynamics in Caenorhabditis elegans early embryos."

Zhang H, White JG, Squirrell JM

[Mol Biol Cell, 2008]

Monitoring Editor: Sean Munro Alignment of the mitotic spindle along a pre-formed axis of polarity is crucial for generating cell diversity in many organisms (Segal and Bloom, 2001; Betschinger and Knoblich, 2004), yet little is known about the role of the endomembrane system in this process. RAB-11 is a small GTPase enriched in recycling endosomes. When we depleted RAB-11 by RNAi in C. elegans, the spindle of the one-cell embryo failed to align along the axis of polarity in metaphase and underwent violent movements in anaphase. The distance between astral microtubules ends and the anterior cortex was significantly increased in rab-11(RNAi) embryos specifically during metaphase, possibly accounting for the observed spindle alignment defects. Additionally, we found that normal ER morphology requires functional RAB-11, particularly during metaphase. We hypothesize that RAB-11, in conjunction with the ER, acts to regulate cell cycle specific changes in astral microtubule length to ensure proper spindle alignment in C. elegans early embryos.