Premium
Functional analyses of mouse ASK, an activation subunit for Cdc7 kinase, using conditional ASK knockout ES cells
Author(s) -
Yamashita Nobuyuki,
Kim JungMin,
Koiwai Osamu,
Arai Kenichi,
Masai Hisao
Publication year - 2005
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1111/j.1365-2443.2005.00857.x
Subject(s) - biology , ask price , kinase , autophosphorylation , microbiology and biotechnology , mutant , protein subunit , biochemistry , protein kinase a , gene , economy , economics
ASK (activator of S phase kinase) is an activation subunit for mammalian Cdc7 kinase. We have generated mutant ES cell lines in which ASK can be conditionally inactivated. Upon loss of the ASK genes, the mutant ES cells rapidly cease cell growth. In keeping with its expected roles in activation of the essential S phase kinase, DNA synthesis is arrested and significant cell death is eventually induced in ASK‐deficient cells, demonstrating essential roles of ASK for viability of ES cells. Using these mutant cells, we have set up a system where ASK molecules can be functionally dissected. In keeping with previous results from yeasts, conserved motif‐M and motif‐C were shown to be essential for in vivo functions of ASK, whereas a long C‐terminal tail, found only in ASK‐related molecules in higher eukaryotes, is not required. Unexpectedly, the motif‐N, related to the BRCT motif and dispensable for viability in yeasts, is essential for the viability of ES cells. Further characterization reveals that motif‐N is required for the maximum phosphorylation of MCM in cells, whereas the autophosphorylation activity of Cdc7 is not significantly affected by its loss. These results may suggest that motif‐N of ASK may facilitate recruitment of substrates for Cdc7 kinase.