Ase1A

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The provisional identification of this gene as Ase1 is supported by its threefold overexpression in a Dicty strain lacking the Dicty retinoblastoma-like gene rblA (Doquang et al, in preparation). Most genes whose products are involved in cell cycle progression are overexpressed in this strain.

Ase1 is a microtubule associated protein, resident in the midbody of the mitotic spindle; it is phosphorylated by cdk1 during mitotic entry, dephosphorylated by the mitotic-exit specific phosphatase cdc14, and degraded by the anaphase promoting complex (see Khmelinskii and Schiebel, Cell Cycle 7, 283-6 (2008). In budding yeast, ase1 is required for spindle elongation and stabilization.

Harry MacWilliams, May 2009

Dicty actually has two Ase1 family genes. The other one, DDB_G0284219 is not retinoblastoma-regulated (overexpression factor 1.09). Comparison of the two genes in a cell cycle synchronization experiment shows that DDB_G0280249 is mainly expressed shortly before cells enter mitosis/Sphase. The roughly 2.5 to 3-fold increase at T1, over the level in unsychronized cells, is comparable to the 2.9-fold maximal increase in BrdU labelling. This gene may thus be expressed near-exclusively in a short pre-mitotic period. The cell-cycle modulation of DDB_G0280249 seems greater than one would expect from its retinoblastoma regulation alone, and additional factors may be involved.

DDB_G0284219, in contrast, shows a flat expression profile throughout the cell cycle. In DictyExpress, DDB_G0280249 shows the developmental profile typical of cell cycle genes in both Dd and Dp, while the developmental trajectory of DDB_G0284219 is flat in both species. The differing expression profiles of the two genes thus suggest that DDB_G0280249 functions in mitosis, while DDB_G0284219 has mainly interphase functions.

HKM July 2010

Image:ase1 family genes.tif



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