High impact information on GIN4

• Enhancement of microtubule shrinkage at the bud neck required the Par-1-related, septin-dependent kinases (SDK) Hsl1 and Gin4 [1].
• Members of the septin family bind directly to Gin4, demonstrating that the functions of Gin4 and the septins must be closely linked within the cell [2].
• In budding yeast, a protein kinase called Gin4 is specifically activated during mitosis and functions in a pathway initiated by the Clb2 cyclin to control bud growth [2].
• Loss of septin function produces a phenotype that is very similar to the phenotype caused by loss of Gin4 function, and the septins are required early in mitosis to activate Gin4 kinase activity [2].
• Affinity chromatography experiments demonstrate that Gin4 binds tightly to Nap1, indicating that the functions of these two proteins are closely tied within the cell [3].

Biological context of GIN4

• 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 [4].
• Hsl1/Nik1, Kcc4 and Gin4 are structurally homologous protein kinases that localize to the bud neck and negatively regulate Swe1 by phosphorylation [4].
• Overexpression of the GIN4 and GIN12 sequences induced elongated buds and a G2/M arrest-like phenotype, respectively [5].
• Gin4 becomes hyperphosphorylated when cells enter mitosis, leading to activation of Gin4 kinase activity [6].
• We have used genetics and biochemistry to identify additional proteins that function with Gin4 in this pathway, and both of these approaches have identified members of the septin family [2].

Associations of GIN4 with chemical compounds

• GIN4 encodes a protein with strong homology to the Snflp serine/threonine kinase [7].

Physical interactions of GIN4

• Nis1 was found to bind Gin4 and Kcc4 in the two-hybrid assay [8].

Enzymatic interactions of GIN4

• Thus, Elm1 regulates the septin assembly-dependent cellular events by directly phosphorylating and activating the Gin4-dependent pathway(s) [9].
• In vitro studies with purified recombinant proteins demonstrated that Elm1 directly phosphorylates and activates Gin4, which in turn phosphorylates Shs1 [9].

Regulatory relationships of GIN4

• Taken together, these findings suggest that highly regulated protein-binding events ensure that the Gin4 kinase is activated only during mitosis and only in association with Shs1, a likely in vivo substrate of Gin4 [6].
• Evidence is presented which suggests that the hyperphosphorylated form of Cla4 is responsible for relaying the signal to activate Gin4 [10].

Other interactions of GIN4

• Moreover, Hsl1, Kcc4, and Gin4 have homologs in higher eukaryotes, suggesting that the regulation of Swe1/Wee1 by this class of kinases is highly conserved [11].
• Kcc4, like Hsl1 and Gin4, was found to localize to the bud neck in a septin-dependent fashion [11].
• Genetic data support the idea that Shs1 is an important target of Gin4 kinase activity [6].
• In this pathway, Clb2 initiates a series of events that lead to the mitosis-specific activation of the Gin4 protein kinase [10].
• In Saccharomyces cerevisiae, additional functions have been ascribed to Nap1, as it has been shown to interact with Clb2 (B type cyclin) and Gin4 (septum formation) [12].

References