Chemical genetic analysis of the regulatory role of Cdc2p in the<i>S. pombe</i>septation initiation network

Dischinger, Sandra; Krapp, Andrea; Xie, Linfeng; Paulson, James R.; Simanis, Viesturs

doi:10.1242/jcs.021584

Cited by 73 publications

(81 citation statements)

References 103 publications

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“…Our work confirms and extends previous work (17) showing that Clp1 dampens Cdk1 activity by dephosphorylating and inactivating Cdc25. Clp1 facilitates proper contractile ring dynamics and timely cytokinesis by antagonizing Cdk1 phosphorylations that negatively regulate the septation initiation network (SIN) and antagonize contractile ring formation (26,(32)(33)(34)(35). Our data show that abrogation of Clp1-Cdc25 feedback reduces the abruptness of cytokinesis.…”

Section: Discussionmentioning

confidence: 75%

Multisite phosphoregulation of Cdc25 activity refines the mitotic entrance and exit switches

Lu¹,

Domingo-Sananes

Huzarska³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Cyclin-dependent kinase 1 (Cdk1) kinase dephosphorylation and activation by Cdc25 phosphatase are essential for mitotic entry. Activated Cdk1 phosphorylates Cdc25 and other substrates, further activating Cdc25 to form a positive feedback loop that drives the abrupt G2/mitosis switch. Conversely, mitotic exit requires Cdk1 inactivation and reversal of Cdk1 substrate phosphorylation. This dephosphorylation is mediated, in part, by Clp1/Cdc14, a Cdk1-antagonizing phosphatase, which reverses Cdk1 phosphorylation of itself, Cdc25, and other Cdk1 substrates. Thus, Cdc25 phosphoregulation is essential for proper G2-M transition, and its contributions to cell cycle control have been modeled based on studies using Xenopus and human cell extracts. Because cell extract systems only approximate in vivo conditions where proteins interact within dynamic cellular environments, here, we use Schizosaccharomyces pombe to characterize, both experimentally and mathematically, the in vivo contributions of Cdk1-mediated phosphorylation of Cdc25 to the mitotic transition. Through comprehensive mapping of Cdk1 phosphosites on Cdc25 and characterization of phosphomutants, we show that Cdc25 hyperphosphorylation by Cdk1 governs Cdc25 catalytic activation, the precision of mitotic entry, and unvarying cell length but not Cdc25 localization or abundance. We propose a mathematical model that explains Cdc25 regulation by Cdk1 through a distributive and disordered phosphorylation mechanism that ultrasensitively activates Cdc25. We also show that Clp1/Cdc14 dephosphorylation of Cdk1 sites on Cdc25 controls the proper timing of cell division, a mechanism that is likely due to the double negative feedback loop between Clp1/Cdc14 and Cdc25 that controls the abruptness of the mitotic exit switch. mitotic bistability | multisite phosphorylation

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Section: Discussionmentioning

confidence: 75%

Multisite phosphoregulation of Cdc25 activity refines the mitotic entrance and exit switches

Lu¹,

Domingo-Sananes

Huzarska³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…In contrast, the data presented here and in previous studies clearly indicate that PP2A (directly or indirectly) inhibits the SIN, which is required for cytokinesis, the last step in the cell cycle. The reason for this difference in organization is unclear; however, we note that the SIN is inhibited by mitotic CDK (Dischinger et al 2008), so it is possible that the regulatory elements coordinating mitosis and cytokinesis are organized differently in S. pombe. For example, other phosphoprotein phosphatases, such as Flp1p/Clp1p and PP1 complexes may be more important for mitotic exit than PP2A.…”

Section: Pp2a and Sin Signalingmentioning

confidence: 89%

Section: Septation Initiation Networkmentioning

confidence: 99%

“…Analysis of the localization of SIN proteins and their activity in mutant backgrounds has led to the proposition that the order of action of the SIN proteins in the mitotic cell cycle is Cdc7p-Spg1p, then Sid1p-Cdc14p, and finally Sid2p-Mob1p (Sparks et al 1999;Guertin et al 2000). Active Cdc2p inhibits the SIN early in mitosis, and CDK inactivation is required for septum formation (Yamano et al 1996;He et al 1997;Guertin et al 2000;Chang et al 2001;Dischinger et al 2008).Components of the SIN have been conserved through evolution; in Saccharomyces cerevisiae, the equivalent signaling network is known as the mitotic exit network (MEN), which regulates mitotic exit and is also important for cytokinesis (reviewed by Bedhomme et al 2008;Meitinger et al 2012). The SIN/MEN protein kinases belong to the nuclear DBF-2-related (NDR) and Ste20 families, the mammalian counterparts of which are important in cell proliferation and growth control (Zhang et al 2009;Zhao et al 2011).…”

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confidence: 99%

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Characterization of ypa1 and ypa2, the Schizosaccharomyces pombe Orthologs of the Peptidyl Proyl Isomerases That Activate PP2A, Reveals a Role for Ypa2p in the Regulation of Cytokinesis

Goyal

2012

Genetics

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The Schizosaccharomyces pombe septation initiation network (SIN) regulates cytokinesis. Cdc7p is the first kinase in the core SIN; we have screened genetically for SIN regulators by isolating cold-sensitive suppressors of cdc7-24. Our screen yielded a mutant in SPAC1782.05, one of the two fission yeast orthologs of mammalian phosphotyrosyl phosphatase activator. We have characterized this gene and its ortholog SPAC4F10.04, which we have named ypa2 and ypa1, respectively. We find that Ypa2p is the major form of protein phosphatase type 2A activator in S. pombe. A double ypa1-D ypa2-D null mutant is inviable, indicating that the two gene products have at least one essential overlapping function. Individually, the ypa1 and ypa2 genes are essential for survival only at low temperatures. The ypa2-D mutant divides at a reduced cell size and displays aberrant cell morphology and cytokinesis. Genetic analysis implicates Ypa2p as an inhibitor of the septation initiation network. We also isolated a cold-sensitive allele of ppa2, the major protein phosphatase type 2A catalytic subunit, implicating this enzyme as a regulator of the septation initiation network. SCHIZOSACCHAROMYCES pombe cells take the form of a cylinder capped by hemispherical ends. During interphase, cells grow mainly at their tips. Cell elongation ceases after mitotic commitment, and the cytoskeleton is reorganized in preparation for nuclear and cell division (reviewed by McCully and Robinow 1971;Mitchison and Nurse 1985;Marks et al. 1986;Hagan and Hyams 1988;Hagan 1998). The cell divides by fission after forming a septum in the middle of the cell. The site of division is defined at the onset of mitosis (Daga and Chang 2005), by the formation of an actomyosin contractile ring (CAR), whose assembly continues throughout mitosis (Wu et al. 2003;Pollard 2008;Pollard and Wu 2010). At the end of anaphase, the CAR is thought to guide synthesis of the multilayered division septum (reviewed by (Ishiguro 1998;Sipiczki 2007). Septation Initiation NetworkThe S. pombe septation initiation network (SIN) is a network of protein kinases that is essential for cytokinesis in the mitotic cycle; reviewed by (Gould and Simanis 1997;Simanis 2003;Wolfe and Gould 2005;Goyal et al. 2011). It is tightly regulated through the mitotic cell cycle to assure proper coordination of mitosis and cytokinesis, and during meiosis, where it is essential for spore formation (Krapp et al. 2006). Signaling requires the activity of three protein kinases, each of which has a regulatory subunit (kinase regulator); Cdc7p-Spg1p (Fankhauser and Simanis 1994;Schmidt et al. 1997;Mehta and Gould 2006), Sid1p-Cdc14p (Fankhauser and Simanis 1993;Guertin et al. 2000;Guertin and McCollum 2001), and Sid2p-Mob1p (Sparks et al. 1999;Hou et al. 2000;Salimova et al. 2000). SIN signaling is modulated by the nucleotide status of the GTPase Spg1p (Schmidt et al. 1997;Sohrmann et al. 1998), which is determined by the balance of spontaneous nucleotide exchange, a putative GEF, Etd1p Garcia-Cortes and McCollu...

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“…The transition is inhibited by an active SAC. Previous studies have shown that Cdc2p inactivation promotes the transition to the asymmetric state of the SIN (Chang et al, 2001;Dischinger et al, 2008;Yamano et al, 1996), suggesting that the SAC effect results from delayed inactivation of Cdc2p.…”

Section: What Regulates the Early-late Transition?mentioning

confidence: 96%

Analysis ofS. pombeSIN protein SPB-association reveals two genetically separable states of the SIN

Wachowicz

Chasapi

Krapp

et al. 2014

Journal of Cell Science

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The Schizosaccharomyces pombe septation initiation network (SIN) regulates cytokinesis, and asymmetric association of SIN proteins with the mitotic spindle pole bodies (SPBs) is important for its regulation. Here, we have used semi-automated image analysis to study SIN proteins in large numbers of wild-type and mutant cells. Our principal conclusions are: first, that the association of Cdc7p with the SPBs in early mitosis is frequently asymmetric, with a bias in favour of the new SPB; second, that the early association of Cdc7p-GFP to the SPB depends on Plo1p but not Spg1p, and is unaffected by mutations that influence its asymmetry in anaphase; third, that Cdc7p asymmetry in anaphase B is delayed by Pom1p and by activation of the spindle assembly checkpoint, and is promoted by Rad24p; and fourth, that the length of the spindle, expressed as a fraction of the length of the cell, at which Cdc7p becomes asymmetric is similar in cells dividing at different sizes. These data reveal that multiple regulatory mechanisms control the SIN in mitosis and lead us to propose a two-state model to describe the SIN.

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Chemical genetic analysis of the regulatory role of Cdc2p in theS. pombeseptation initiation network

Cited by 73 publications

References 103 publications

Multisite phosphoregulation of Cdc25 activity refines the mitotic entrance and exit switches

Multisite phosphoregulation of Cdc25 activity refines the mitotic entrance and exit switches

Characterization of ypa1 and ypa2, the Schizosaccharomyces pombe Orthologs of the Peptidyl Proyl Isomerases That Activate PP2A, Reveals a Role for Ypa2p in the Regulation of Cytokinesis

Analysis ofS. pombeSIN protein SPB-association reveals two genetically separable states of the SIN

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