Activation of Srk1 by the Mitogen-activated Protein Kinase Sty1/Spc1 Precedes Its Dissociation from the Kinase and Signals Its Degradation

López-Avilés, Sandra; Lambea, Eva; Moldón, Alberto; Grande, Maribel; Fajardo, Alba; Gabriel, M.; Hidalgo, Elena; Aligué, Rosa

doi:10.1091/mbc.e07-07-0639

Cited by 35 publications

(49 citation statements)

References 17 publications

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“…StyI MAPK, the Hog1 homologue in Schizosaccharomyces pombe, delays the cell cycle during the G 2 /M phase in response to osmostress by regulating Cdc25 localization (55). Interestingly, StyI regulation of Cdc25 is independent of Wee1 function, similar to the cell wall integrity checkpoint being independent of Swe1 (3,56).…”

Section: Discussionmentioning

confidence: 99%

The Late S-Phase Transcription Factor Hcm1 Is Regulated through Phosphorylation by the Cell Wall Integrity Checkpoint

Negishi

Veis

Hollenstein

et al. 2016

Molecular and Cellular Biology

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The cell wall integrity (CWI) checkpoint in the budding yeast Saccharomyces cerevisiae coordinates cell wall construction and cell cycle progression. In this study, we showed that the regulation of Hcm1, a late-S-phase transcription factor, arrests the cell cycle via the cell wall integrity checkpoint. Although the HCM1 mRNA level remained unaffected when the cell wall integrity checkpoint was induced, the protein level decreased. The overproduction of Hcm1 resulted in the failure of the cell wall integrity checkpoint. We identified 39 Hcm1 phosphorylation sites, including 26 novel sites, by tandem mass spectrometry analysis. A mutational analysis revealed that phosphorylation of Hcm1 at S61, S65, and S66 is required for the proper onset of the cell wall integrity checkpoint by regulating the timely decrease in its protein level. Hyperactivation of the CWI mitogen-activated protein kinase (MAPK) signaling pathway significantly reduced the Hcm1 protein level, and the deletion of CWI MAPK Slt2 resulted in a failure to decrease Hcm1 protein levels in response to stress, suggesting that phosphorylation is regulated by CWI MAPK. In conclusion, we suggest that Hcm1 is regulated negatively by the cell wall integrity checkpoint through timely phosphorylation and degradation under stress to properly control budding yeast proliferation. Critical events during cell cycle progression, such as DNA replication and mitosis, are regulated by cell cycle checkpoints to ensure the proper completion of cell division. The cell cycle in the budding yeast Saccharomyces cerevisiae is coordinated with bud growth to secure the morphological space for cell division (1). One of the cell cycle checkpoints required to monitor budding morphology is the morphogenesis checkpoint (2), and the other is the cell wall integrity (CWI) checkpoint (3). They function independently to coordinate bud growth and cell wall construction, respectively, with cell cycle progression (4). Without a supply of cell wall materials for bud growth, the budding yeast cell cycle is arrested before entry into M phase and cannot proceed to mitosis (3).Compared to the morphogenesis checkpoint that regulates Swe1 phosphorylation and its degradation to activate cyclin-dependent kinase (CDK) (5), the primary function of the cell wall integrity checkpoint is inhibiting cell cycle progression to mitosis, which is achieved essentially by downregulating M-phase cyclin CLB2 (3, 4). During functions of the active cell wall integrity checkpoint, cells accumulate at the small budded state. Budding starts as cells proceed to S phase; thus, the checkpoint must be activated during S phase to prevent later cell cycle events. However, the manner by which the regulatory signaling cascade induced by the cell wall integrity checkpoint feeds into the complex transcriptional network of cell cycle progression has not been fully investigated. Genome-wide transcriptional studies have revealed the transcription cascade of cell cycle-related transcription factors (6-9). Studies have shown major tr...

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Section: Discussionmentioning

confidence: 99%

The Late S-Phase Transcription Factor Hcm1 Is Regulated through Phosphorylation by the Cell Wall Integrity Checkpoint

Negishi

Veis

Hollenstein

et al. 2016

Molecular and Cellular Biology

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“…Phosphorylated Srk1 blocks mitotic onset by inhibiting the activity of the Cdc25 phosphatase that is required to activate maturation-promoting factor (MPF) (LopezAviles et al, 2005;Lopez-Aviles et al, 2008). Because Sty1 both promotes and delays mitotic onset, an extra layer of regulation is likely to be needed.…”

Section: Mapk Control Of Mitotic Onsetmentioning

confidence: 99%

“…This model would predict that Srk1 would need a high threshold of activation before it becomes phosphorylated. Interestingly, the site in Srk1 that is phosphorylated by Sty1 is ARTP (Lopez-Aviles et al, 2008) (amino acid shown in bold indicates phosphorylation site), which differs from the optimal MAPK consensus sites PX(S/T)P and so might require a high level of Sty1 activity for phosphorylation and thus inhibition of mitosis.…”

Section: Mapk Control Of Mitotic Onsetmentioning

confidence: 99%

Fission yeast Tor1 functions as part of TORC1 to control mitotic entry through the stress MAPK pathway following nutrient stress

Hartmuth

Petersen

2009

Journal of Cell Science

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TOR signalling coordinates growth and division to control cell size. Inhibition of Schizosaccharomyces pombe Tor1, in response to a reduction in the quality of the nitrogen source (nutrient stress), promotes mitotic onset through activation of the mitogen-activated protein kinase (MAPK) Sty1 (also known as Spc1). Here we show that `nutrient starvation' (complete withdrawal of nitrogen or leucine) blocks mitotic commitment by altering Sty1 signalling and that different degrees of Sty1 activation determine these differences in mitotic commitment decisions. Mammals contain one TOR kinase, whereas yeasts contain two. In each case, they comprise two distinct complexes: TORC1 and TORC2. We find that nutrient-stress-induced control of mitotic onset, through Tor1, is regulated through changes in TORC1 signalling. In minimal medium, Tor1 interacts with the TORC1 component Mip1 (raptor), and overexpression of tor1+ generates growth defects reminiscent of TORC1 mutants. Strains lacking the TORC2-specific components Sin1 and Ste20 (rictor) still advance mitotic onset in response to nutrient stress. By contrast, Mip1 and the downstream effector Gad8 (a S6K kinase homologue), like Tor1, are essential for nutrient stress to advance mitotic onset. We conclude that S. pombe Tor1 and Tor2 can both act in TORC1. However, it is the inhibition of Tor1 as part of TORC1 that promotes mitosis following nutrient stress.

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“…Spc1 also promotes meiosis by inducing the expression of the transcriptional factor Ste11, a regulator involved in sexual development (16). Under osmotic stress, Spc1 interacts with and phosphorylates the Ser/Thr kinase Srk1, which results in a transitory G 2 /M cell cycle arrest (17), while Srk1 overexpression inhibits the cell cycle arrest in G 1 , under nitrogen starvation. In addition, Srk1 has a regulatory role in meiosis, as null Srk1 mutants enter meiosis earlier than the wild-type strain (18).…”

mentioning

confidence: 99%

The SrkA Kinase Is Part of the SakA Mitogen-Activated Protein Kinase Interactome and Regulates Stress Responses and Development in Aspergillus nidulans

et al. 2015

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cFungi and many other eukaryotes use specialized mitogen-activated protein kinases (MAPK) of the Hog1/p38 family to transduce environmental stress signals. In Aspergillus nidulans, the MAPK SakA and the transcription factor AtfA are components of a central multiple stress-signaling pathway that also regulates development. Here we characterize SrkA, a putative MAPK-activated protein kinase, as a novel component of this pathway. ⌬srkA and ⌬sakA mutants share a derepressed sexual development phenotype. However, ⌬srkA mutants are not sensitive to oxidative stress, and in fact, srkA inactivation partially suppresses the sensitivity of ⌬sakA mutant conidia to H 2 O 2 , tert-butyl-hydroperoxide (t-BOOH), and menadione. In the absence of stress, SrkA shows physical interaction with nonphosphorylated SakA in the cytosol. We show that H 2 O 2 induces a drastic change in mitochondrial morphology consistent with a fission process and the relocalization of SrkA to nuclei and mitochondria, depending on the presence of SakA. SakA-SrkA nuclear interaction is also observed during normal asexual development in dormant spores. Using SakA and SrkA S-tag pulldown and purification studies coupled to mass spectrometry, we found that SakA interacts with SrkA, the stress MAPK MpkC, the PPT1-type phosphatase AN6892, and other proteins involved in cell cycle regulation, DNA damage response, mRNA stability and protein synthesis, mitochondrial function, and other stress-related responses. We propose that oxidative stress induces DNA damage and mitochondrial fission and that SakA and SrkA mediate cell cycle arrest and regulate mitochondrial function during stress. Our results provide new insights into the mechanisms by which SakA and SrkA regulate the remodelling of cell physiology during oxidative stress and development. W e have proposed that when life was confronted with oxidative stress, cells evolved mechanisms not only to defend against reactive oxygen species (ROS) but also to use this ancestral form of stress to regulate their own growth and differentiation (1, 2). Indeed, the regulated production of ROS by enzymes of the NADPH oxidase family (NOX) is essential for sexual differentiation in Aspergillus nidulans (3) and Neurospora crassa and for polar growth and cell fusion in N. crassa (4), and NOX enzymes play multiple signaling functions in other fungal (5-10), animal, and plant species (11). However, little is known about ROS perception and the mechanisms by which ROS exert their signaling functions.The use of phosphorelay systems to perceive oxidative stress and other types of environmental stress is conserved in bacteria, plants (12), and fungi (13). The fission yeast Schizosaccharomyces pombe uses a multistep phosphorelay composed of the Mak2/3 sensor histidine kinases, Mpr1 HPt protein, and Mcs4 response regulator to transmit H 2 O 2 stress signals to the Spc1 (also known as StyI) mitogen-activated protein kinase (MAPK) cascade (14,15). Spc1 is homologous to Saccharomyces cerevisiae Hog1 and mammalian p38 MAPKs, which are also...

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Activation of Srk1 by the Mitogen-activated Protein Kinase Sty1/Spc1 Precedes Its Dissociation from the Kinase and Signals Its Degradation

Cited by 35 publications

References 17 publications

The Late S-Phase Transcription Factor Hcm1 Is Regulated through Phosphorylation by the Cell Wall Integrity Checkpoint

The Late S-Phase Transcription Factor Hcm1 Is Regulated through Phosphorylation by the Cell Wall Integrity Checkpoint

Fission yeast Tor1 functions as part of TORC1 to control mitotic entry through the stress MAPK pathway following nutrient stress

The SrkA Kinase Is Part of the SakA Mitogen-Activated Protein Kinase Interactome and Regulates Stress Responses and Development in Aspergillus nidulans

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