Tousled-like kinases (TLKs) constitute a family of serine/threonine kinases conserved in multi-cellular organisms and have important functions during cell-cycle progression. Altering TLK activity in loss or gain-of-function experiments caused aberrant chromosome morphology and arrested nuclear divisions. Human and fly TLKs appear to function in chromosome assembly and nuclear division, at least in part, through phosphorylation of histone H3 and histone chaperone protein Asf-1 (anti-silencing function protein 1) (Li Y. et al, 2001; Carrera P. et al, 2003). Our studies of the
tlk-1 gene by RNAi showed that
tlk-1 is important for DNA condensation and segregation during mitosis. In
tlk-1(RNAi) embryos, mitotic DNA was not condensed normally and DNA segregation defects were observed. The phosphorylation of histone H3 has been implicated in mitotic DNA condensation. However, histone H3 was still phosphorylated in tlk(RNAi) mutants as detected by immuno-staining using the antibody against phospho-histone H3 (Han Z. et al, 2003).To understand how TLK-1 functions, we performed a yeast two-hybrid screen using TLK-1 as bait. In a pilot screen, we obtained TLK-1-interacting proteins with previously identified roles in translation, ubiquitination, signal transduction, cell-cycle regulation or cytoplasmic cargo translocation. We are currently testing the physiological significance of the interactions and performing a large-scale yeast two-hybrid screen for more TLK-1 interacting candidates. In parallel, we are establishing a TLK-1 kinase assay using the TLK-1 protein expressed in the baculovirus system. References 1.Carrera, P., Moshkin, Y.M., Gronke, S., Sillje, H.H.W., Nigg, E.A., Jackle, H., and Karch, F. (2003) Genes & Dev., 17, 2578-2590. 2.Han, Z., Saam J.R., Adams, H.P., Mango S.E., and Schumacher, J.M. (2003) Curr. Biol., 13, 1921-1929. 3.Li, Y., DeFatta, R., Anthony, C., Sunavala, G., and DeBenedetti, A. (2001) Oncogene, 20, 726-738.