Transmitting meiotic signals in yeast: lipases, lipid anchors,
checkpoint controls.
Gela Tevzadze, Rochelle Easton
Esposito
Molecular Genetics & Cell Biol, University of Chicago, 920
East 58th Street, Chicago, IL 60637, USA
The spindle pole body (SPB)
plays a unique role during yeast meiosis initiating both spindle
assembly and spore wall synthesis. Spo1, a meiosis-specific
phospholipase B (PLB) homolog, is required for SPB morphogenesis during
meiosis and spore formation in yeast (Tevzadze et al.; 2000
Chromosoma 109: 72). Since PLB enzymes can act upon lipid
molecules to generate lysophospholipids that function as second
messengers, we have suggested Spo1 may be part of a novel meiosis-specific signaling pathway controlling the dual roles of the SPB during
gametogenesis. Several lines of evidence suggest that Spo1 utilizes
phosphatidylinositol (PI) as a substrate, including high-copy
suppression of spo1 by glycosylphosphatidyl-inositol(GPI) lipid-anchored proteins (e.g., Cwp1 and Spo19), partial suppression by
PLB3 (PI-specific PLB) under the SPO1 promoter, and recent
genome-wide analysis of PI-binding proteins (Zhu et al.; 2001
Science 293: 2101). Mutant suppressors allowing
sporulation of spo1 were obtained in a screen for downstream
targets of Spo1 signaling. One of these is allelic to SPO73, a
meiosis-specific gene required for spore wall formation and encoding a
protein containing a Fe-S domain, also found in PI-specific kinases.
Wild-type SPO73 has both positive and negative functions in
meiosis, suggesting Spo73p acts as a transmitter of a Spo1-generated
signal, allowing the progression of meiosis in the presence of Spo1 and
acting as a novel checkpoint when SPB development is abnormal.
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