Alternative titles; symbolsCOILED-COIL DOMAIN-CONTAINING PROTEIN 99; CCDC99SPINDLY, DROSOPHILA, HOMOLOG OFHGNC Approved Gene Symbol: SPDL1Cytogenetic location: 5...
Alternative titles; symbols
HGNC Approved Gene Symbol: SPDL1
Cytogenetic location: 5q35.1 Genomic coordinates (GRCh38): 5:169,583,660-169,604,777 (from NCBI)
Mitotic spindle formation and chromosome segregation depends on kinetochore-microtubule interactions. SPDL1 transiently interacts with a protein complex on kinetochores and promotes recruitment of dynein microtubule motor proteins (see 600112) for chromosome attachment to microtubules and formation of the metaphase plate (summary by Barisic et al., 2010).
▼ Cloning and Expression
By searching databases for sequences similar to a conserved 32-amino acid motif in insect Spindly proteins, Griffis et al. (2007) identified human SPDL1, which they called Spindly. The deduced 605-amino acid human protein has the conserved 32-amino acid motif between 2 coiled-coil domains. Drosophila Spindly is longer than the human protein, and the proteins share only 14% identity overall. However, human and Drosophila Spindly share 56% identity in their conserved 32-amino acid motifs and have similar coiled-coil organizations. Immunohistochemical analysis of HeLa cells showed colocalization of Spindly with CENPA (117139) on kinetochores during mitosis. Database analysis revealed orthologs of Spindly in insects, but not in more distant species.
By immunohistochemical analysis of mitotic HeLa cells, Chan et al. (2009) found that Spindly localized to kinetochores in early prometaphase, relocalized to spindle poles before metaphase, and was lost in anaphase and telophase. Spindly colocalized with BUBR1 (BUB1B; 602860), indicating that it is an outer kinetochore protein. Western blot analysis of HeLa cells detected endogenous Spindly at an apparent molecular mass of 70 kD, consistent with its calculated molecular mass.
Barisic et al. (2010) reported that the human Spindly protein has 2 coiled-coil domains separated by a conserved Spindly box, as well as a QQ motif at the C terminus. Spindly also has several sites for serine phosphorylation. In synchronized HeLa and U2OS cells, Spindly expression oscillated during the cell cycle and peaked in mitosis.
▼ Gene Function
Griffis et al. (2007) found that small interfering RNA (siRNA)-mediated knockdown of Spindly in HeLa cells resulted in an increased ratio of metaphase cells to anaphase cells, misaligned chromosomes, reduced stretch between paired centromeres, and reduced colocalization of dynein with CENPA.
Using coimmunoprecipitation analysis and gradient centrifugation of HeLa cell proteins, Chan et al. (2009) determined that Spindly intermittently interacted with the RZZ kinetochore protein complex made up of ROD (KNTC1; 607363), ZW10 (603954), and ZWILCH (609984). Spindly stability was reduced by depletion of ZW10 or by depletion or inhibition of the mitotic kinase Aurora B (AURKB; 604970). Depletion of Spindly in mitotic HeLa cells via siRNA resulted in elongated spindles, severe chromosome misalignment, and mitotic delay. Knockdown of Spindly interfered with loading of dynein intermediate subunit (see 603772) and dynactin subunit p150(Glued) (DCTN1; 601143) onto kinetochores and reduced kinetochore tension. Chan et al. (2009) concluded that Spindly forms transient and dynamic interactions with the RZZ complex on kinetochores and recruits the dynein/dynactin complex to complete kinetochore-microtubule interactions during mitosis.
Barisic et al. (2010) presented findings similar to those of Griffis et al. (2007) and Chan et al. (2009). In addition, they identified multiple regions of human Spindly that mediated its kinetochore or mitotic spindle localization. Knockdown of Spindly in HeLa cells induced MAD2 (MAD2L1; 601467)-dependent prometaphase arrest, in addition to causing multiple spindle defects. Codepletion of the RZZ subunit ZW10 rescued chromosome congression defects in Spindly-knockdown cells. Barisic et al. (2010) concluded that Spindly is a kinetochore tether for dynein and is also involved in coordinating microtubule attachment and mitotic checkpoint signaling.
Hartz (2015) mapped the SPDL1 gene to chromosome 5q35.1 based on an alignment of the SPDL1 sequence (GenBank AK000371) with the genomic sequence (GRCh38).