| Abstrakt: |
The ssp1gene encodes a protein kinase involved in alteration of cell polarity in Schizosaccharomyces pombe. ssp1deletion causes stress sensitivity, reminiscent of defects in the stress-activated MAP kinase, Spc1; however, the two protein kinases do not act through the same pathway. Ssp1 is localized mainly in the cytoplasm, but after a rise in external osmolarity it is rapidly recruited to the plasma membrane, preferentially to active growth zones and septa. Loss of Ssp1 function inhibits actin relocalization during osmotic stress, incdc3and cdc8mutant backgrounds, and in the presence of latrunculin A, implicating Ssp1 in promotion of actin depolymerization. We propose a model in which Ssp1 can be activated independently of Spc1 and can partially compensate for its loss. Thessp1deletion mutant exhibited monopolar actin distribution, but new end take-off (NETO) could be induced in these cells by exposure to KCl or to latrunculin A pulse treatment. This treatment induced NETO in cdc10cells arrested in G1 but not in tea1cells. This suggests that cells that contain intact cell end markers are competent to undergo NETO throughout interphase, and Ssp1 is involved in generating the NETO stimulus by enlarging the actin monomer pool. |
