Adenylyl cyclase is dispensable for vegetative cell growth in the fission yeast Schizosaccharomyces pombe.

Abstract

Disruption of the cyri gene of Schizosaccharomyces pombe, which encodes adenylyl cyclase, did not confer lethality to fission yeast cells, although they grew 40% slower than wild-type strains in complete medium. These cells contained no measurable amount of cAMP and no adenylyl cyclase activity. When h' and h-cyri disruptants were mixed, they underwent mating even in rich medium. Propagation of homothallic cyri disruptants was difficult, probably because such cells readily mate and produce asci and thus stop growing. A >10-fold increase in the amount of cyri mRNA was observed when cloned cyrl+ was introduced into Sch. pombe cells on a multicopy plasmid. The total adenylyl cyclase activity was similarly high in these transformants. However, the level of intracellular cAMP was hardly affected. Evidence suggests that this was not due to increased phosphodiesterase activity. Thus, cAMP level in growing fission yeast cells appears to be regulated not by the amount of adenylyl cyclase protein but by a feedback mechanism at the enzyme level. The cAMP level fell by "50% under nitrogen starvation, which triggers sexual development in Sch. pombe. We suggest that fission yeast controls the level of intracellular cAMP primarily to regulate sexual development rather than to drive or arrest the cell cycle.

Promoter-driven splicing regulation in fission yeast

“…Uritani et al, 2006;Weisman et al, 2007). Nitrogen starvation results in the G1 arrest and the transcriptional activation of ste11 (Maeda et al, 1990;Mochizuki and Yamamoto, 1992;Sugimoto et al, 1991): a) Starvation-induced G1 arrest requires the inactivation of the Cdc2-Cig2 complex, which promotes S phase and the Cdc2-Cdc13 complex, which can take over Cig2 function in its absence (Fisher and Nurse, 1996). Degradation of Cig2 delays G1/S transition, which allows the accumulation of Rum1.…”

Ran1 functions to control the Cdc10/Sct1 complex through Puc1.

“…The loss of ranl can be suppressed by overexpression of sctl or pucl, by the loss of stel 1 or mei2, or by conditions that cause unregulated cAMP-dependent kinase (cAPK) activity (Sipiczki, 1988;Sugimoto et al, 1991;Tanaka et al, 1992;for review, see Nielsen et al, 1993;Forsburg and Nurse, 1994). Cells that carry a deletion of the sctl gene or inactivating mutations in ranl, adenylate cyclase (cyrl), or cAPK (pkal) undergo conjugation and subsequent meiosis regardless of nutritional conditions thereby bypassing the normal requirement for nitrogen limitation for activation of these pathways (Iino and Yamamoto, 1985;Nurse, 1985;Maeda et al, 1990;Caligiuri and Beach, 1993;Maeda et al, 1994). The cAMP signaling pathway functions to prevent conjugation and meiosis, whereas Ranl appears to regulate entry into meiosis exclusively.…”

Cyclin B Proteolysis and the Cyclin-dependent Kinase Inhibitor rum1p Are Required for Pheromone-induced G1Arrest in Fission Yeast

“…This genetic background is required to observe P-factor-induced G 1 arrest in exponentially growing cells. Elimination of the adenylate cyclase cyr1 ϩ gene leads to constitutive expression of nutritionally controlled genes, including components of the pheromone signal transduction cascade (Maeda et al, 1990;Kawamukai et al, 1991;; sxa2 ϩ encodes a P-factor-degrading protease (Imai and Yamamoto, 1992;Ladds et al, 1996). Control…”