Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Saccharomyces cerevisiae mitotic exit network (MEN) is a conserved set of genes that mediate the transition from mitosis to G(1) by regulating mitotic cyclin degradation and the inactivation of cyclin-dependent kinase (CDK). Here, we demonstrate that, in addition to mitotic exit, S. cerevisiae MEN gene MOB1 is required for cytokinesis and cell separation. The cytokinesis defect was evident in mob1 mutants under conditions in which there was no mitotic-exit defect. Observation of live cells showed that yeast myosin II, Myo1p, was present in the contractile ring at the bud neck but that the ring failed to contract and disassemble. The cytokinesis defect persisted for several mitotic cycles, resulting in chains of cells with correctly segregated nuclei but with uncontracted actomyosin rings. The cytokinesis proteins Cdc3p (a septin), actin, and Iqg1p/ Cyk1p (an IQGAP-like protein) appeared to correctly localize in mob1 mutants, suggesting that MOB1 functions subsequent to actomyosin ring assembly. We also examined the subcellular distribution of Mob1p during the cell cycle and found that Mob1p first localized to the spindle pole bodies during mid-anaphase and then localized to a ring at the bud neck just before and during cytokinesis. Localization of Mob1p to the bud neck required CDC3, MEN genes CDC5, CDC14, CDC15, and DBF2, and spindle pole body gene NUD1 but was independent of MYO1. The localization of Mob1p to both spindle poles was abolished in cdc15 and nud1 mutants and was perturbed in cdc5 and cdc14 mutants. These results suggest that the MEN functions during the mitosis-to-G(1) transition to control cyclin-CDK inactivation and cytokinesis.
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PMID:Saccharomyces cerevisiae Mob1p is required for cytokinesis and mitotic exit. 1156 80

Candida albicans uses a network of multiple signaling pathways to control the yeast-->hypha transition. These include a mitogen-activated protein kinase pathway through Cph1, the cAMP-dependent protein kinase pathway via Efg1, a pH-responsive pathway through Rim101, the Tup1-mediated repression through Rfg1 and Nrg1, and pathways represented by transcription factors Cph2, Tec1 and Czf1. These pathways control the transcription of a common set of hypha-specific genes, many of which encode known virulence factors. The link between the signaling pathways and hyphal elongation is currently unknown, but there is evidence to suggest that Cdc42 likely plays a key role in hyphal morphogenesis. Unlike pseudohyphal growth in Saccharomyces cerevisiae, hyphal elongation is regulated independently of the cell cycle. Cellular differences between pseudohyphae and hyphae are further revealed by septin localization.
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PMID:Transcriptional control of dimorphism in Candida albicans. 1173 26

Filamentous fungi form multicellular hyphae that are partitioned by septa. In A. nidulans, septum formation requires the assembly of a septal band following the completion of mitosis. Recent observations show that this band is a dynamic structure composed of actin, a septin and a formin. In addition, assembly is dependent upon a conserved protein kinase cascade that regulates mitotic exit and septation in yeast. Hyphal differentiation may reflect the regulation of this cascade by cyclin-dependent kinase activity. In this review, the dynamics and regulation underlying the assembly of the septal band are discussed.
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PMID:Septum formation in Aspergillus nidulans. 1173 27

Studies are presented characterizing platelet CDCrel-1, a protein expressed to high levels by megakaryocytes and belonging to a family of conserved proteins, termed septin. Septin filaments originally were identified in yeast as essential for budding but have become increasingly associated with processes in higher eukaryotic cells involving active membrane movement such as cytokinesis and vesicle trafficking. Direct proof of an in vivo function for septins in higher eukaryotes is limited to the characterization of the Drosophila septin, termed PNUT. We present studies identifying platelet CDCrel-1 as a protein kinase substrate in the presence of known platelet agonists. The immunopurification of CDCrel-1 revealed it to be part of a macromolecular complex containing a protein involved in platelet secretion, syntaxin 4. Moreover, CDCrel-1 was localized in situ to areas surrounding platelet-storage granules. The relevance of CDCrel-1 to normal platelet function was established with the characterization of platelets from a CDCrel-1(Null) mouse. As compared with platelets from wild-type littermates, CDCrel-1(Null) platelets aggregate and release stored [14C]serotonin in the presence of subthreshold levels of collagen. These results provide new insights into the mechanisms regulating platelet secretion and identify platelet septins as a protein family contributing to membrane trafficking within the megakaryocyte and platelet.
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PMID:A prototypic platelet septin and its participation in secretion. 1188 Jun 46

The septins constitute a family of filament-forming proteins ubiquitous in eukaryotic species. We demonstrate here that the Saccharomyces cerevisiae septin, Cdc3, is a substrate of the cell cycle regulatory cyclin-dependent kinase (Cdk), Cdc28. Two serines near the C-terminus of Cdc3 are phosphorylated in a Cdc28-dependent manner. Analysis of a mutant allele that cannot be phosphorylated at these sites revealed an effect of Cdc28 phosphorylation of Cdc3 at the time of budding. Immunofluorescence analysis of wild-type and mutant Cdc3 indicated that prevention of phosphorylation at Cdc28-dependent sites impairs the disassembly of the old septin ring, which is inherited at mitosis but which usually disappears immediately prior to assembly of a new ring. Furthermore, immuno-fluorescence analysis of septin ring dynamics in a G1 cyclin (Cln) mutant suggests that G1 cyclin function is required for efficient ring disassembly. Thus, phosphorylation of Cdc3 by the Cdc28 kinase at the end of G1 may facilitate initiation of a new cell cycle by promoting disassembly of the obsolete septin ring from the previous cell cycle.
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PMID:Phosphorylation of the septin cdc3 in g1 by the cdc28 kinase is essential for efficient septin ring disassembly. 1242 5

Bni4 is a scaffold protein in the yeast Saccharomyces cerevisiae that tethers chitin synthase III to the bud neck by interacting with septin neck filaments and with Chs4, a regulatory subunit of chitin synthase III. We show herein that Bni4 is also a limiting determinant for the targeting of the type 1 serine/threonine phosphatase (Glc7) to the bud neck. Yeast cells containing a Bni4 variant that fails to associate with Glc7 fail to tether Chs4 to the neck, due in part to the failure of Bni4(V831A/F833A) to localize properly. Conversely, the Glc7-129 mutant protein fails to bind Bni4 properly and glc7-129 mutants exhibit reduced levels of Bni4 at the bud neck. Bni4 is phosphorylated in a cell cycle-dependent manner and Bni4(V831A/F833A) is both hyperphosphorylated and mislocalized in vivo. Yeast cells lacking the protein kinase Hsl1 exhibit increased levels of Bni4-GFP at the bud neck. GFP-Chs4 does not accumulate at the incipient bud site in either a bni4::TRP1 or a bni4(V831A/F833A) mutant but does mobilize to the neck at cytokinesis. Together, these results indicate that the formation of the Bni4-Glc7 complex is required for localization to the site of bud emergence and for subsequent targeting of chitin synthase.
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PMID:A Bni4-Glc7 phosphatase complex that recruits chitin synthase to the site of bud emergence. 1252 24

In the budding yeast S. cerevisiae, Swe1 delays the onset of mitosis by phosphorylation and inactivation of the cyclin-dependent kinase Cdc28, thereby relaying the morphogenetic signal to the cell cycle. Hsl1/Nik1, Kcc4 and Gin4 are structurally homologous protein kinases that localize to the bud neck and negatively regulate Swe1 by phosphorylation. We report here that Kcc4 and Gin4 have partially overlapping but essentially distinct cellular functions. Deletion of KCC4 had a similar effect to GIN4 deletion, causing moderate defects in bud formation at stationary phase; overexpression of Kcc4 inhibited cell growth. KCC4 showed functional interaction with GIN4 in cdc28 mutants, and both Kcc4 and Gin4 proteins physically interacted with Swe1 in vitro. However, unlike gin4delta cells, kcc4Delta cells were not elongated but multi-budded at stationary phase, and showed resistance to 0.04% SDS and 0.003% calcofluor white. In light of the observation that Kcc4 and Gin4 specifically associate with distinct septin proteins, we propose that the observed functional distinction between Kcc4 and Gin4 is due to differences in septin association partners.
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PMID:The Saccharomyces cerevisiae bud-neck proteins Kcc4 and Gin4 have distinct but partially-overlapping cellular functions. 1277 12

CLA4, encoding a protein kinase of the PAK type, and CDC11, encoding a septin, were isolated in a screen for synthetic lethality with CHS3, which encodes the chitin synthase III catalytic moiety. Although Ste20p shares some essential function with Cla4p, it did not show synthetic lethality with Chs3p. cla4 and cdc11 mutants exhibited similar morphological and septin localization defects, including aberrant and ectopic septa. Myo1p, which requires septins for localization, formed abnormally wide rings in cla4 mutants. In cultures started with unbudded cells, an inhibitor of Chs3p activity, nikkomycin Z, aggravated the abnormalities of cla4 and cdc11 mutants and gave rise to enlarged necks at the mother-bud junction, leading to cell death. It is concluded that Cla4p is required for the correct localization and/or assembly of the septin ring and that both the septin ring and the Chs3p-requiring chitin ring at the mother-bud neck cooperate in maintaining the neck constricted throughout the cell cycle, a vital function in budding yeast.
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PMID:Septins, under Cla4p regulation, and the chitin ring are required for neck integrity in budding yeast. 1280 80

The assembly of cytoskeletal structures is coupled to other cellular processes. We have studied the molecular mechanism by which assembly of the yeast septin cytoskeleton is monitored and coordinated with cell cycle progression by analyzing a key regulatory protein kinase, Hsl1, that becomes activated only when the septin cytoskeleton is properly assembled. We first identified a regulatory region of Hsl1 that physically associates with the kinase domain and found that it performs an autoinhibitory function both in vivo and in vitro. Several septin binding domains lie near and overlap the inhibitory domain; these are important for Hsl1 function, and binding of two septins, Cdc11 and Cdc12, relieves the autoinhibition imposed by the kinase inhibitory domain in vitro. Our results suggest that binding to multiple septins activates Hsl1 kinase activity, thereby promoting cell cycle progression. The high conservation of Hsl1 indicates that similar mechanisms may monitor cytoskeletal organization in other eukaryotes.
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PMID:Cytoskeletal activation of a checkpoint kinase. 1452 12

The accurate spatial and temporal coordination of cell polarization with DNA replication and segregation guarantees the fidelity of genetic transmission. Here we report that in Saccharomyces cerevisiae, a build-up or burst of G1 cyclin-dependent kinase (CDK) activity through activation of the cyclin genes CLN1,2 and PCL1,2 is essential for cell morphogenesis, but not for other events associated with the G1-S-phase transition, including DNA replication. Strains lacking a burst of late-G1 cyclin-CDK activity (LG1C(-)) undergo a catastrophic morphogenesis and halt the nuclear cycle at the morphogenesis checkpoint in G2 phase. Consistent with a role in morphogenesis, the Pho85 G1 cyclins Pcl1 and Pcl2 show a unique pattern of localization to sites of polarized cell growth, and strains lacking PCL1 and PCL2 show genetic interactions with the cell polarity GTPase Cdc42, its regulators and downstream effectors. Our data suggest that inability to assemble a septin ring and localize the GTP exchange factor Cdc24 at the incipient bud site may be the primary morphogenetic defects in LG1C-depleted cells. We conclude that a burst of late G1 cyclin-CDK activity is essential for establishing cell polarity and development of the cleavage apparatus.
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PMID:Late-G1 cyclin-CDK activity is essential for control of cell morphogenesis in budding yeast. 1468 90


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