The endo-β-1,3-glucanase eng1p is required for dissolution of the primary septum during cell separation in Schizosaccharomyces pombe
2003
Schizosaccharomyces pombe cells divide by medial fission
throughout contraction of an actomyosin ring and deposition of a multilayered
division septum that must be cleaved to release the two daughter cells.
Although many studies have focused on the actomoysin ring and septum assembly,
little information is available concerning the mechanism of cell separation.
Here we describe the characterization of eng1 + , a new gene
that encodes a protein with detectable endo-β-1,3-glucanase activity and
whose deletion is not lethal to the cells but does interfere in their
separation. Electron microscopic observation of mutant cells indicated that
this defect is mainly due to the failure of the cells to degrade the primary
septum, a structure rich in β-1,3-glucans, that separates the two sisters
cells. Expression of eng1 + varies during the cell cycle,
maximum expression being observed before septation, and the protein localizes
to a ring-like structure that surrounds the septum region during cell
separation. This suggests that it could also be involved in the cleavage of
the cylinder of the cell wall that covers the division septum. The expression
of eng1 + during vegetative growth is regulated by a C2H2
zinc-finger protein (encoded by the SPAC6G10.12c ORF), which shows significant
sequence similarity to the Saccharomyces cerevisiae ScAce2p,
especially in the zinc-finger region. Mutants lacking this transcriptional
regulator (which we have named ace2 + ) show a severe cell
separation defect, hyphal growth being observed. Thus, ace2p may regulate the
expression of the eng1 + gene together with that of other
genes whose products are also involved in cell separation.
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