Morphogenesis signaling components influence cell cycle regulation by cyclin dependent kinase

The regulation of the yeast cell cycle is primarily governed by cyclin-dependent kinase (CDK) Cdc28. It was already known that Cdc28 interacts with Swe1, an inhibitory kinase that modulates its activity. However, how morphogenesis signaling affects CDK function remains unclear. Under nutrient-limited conditions, yeast undergoes a dimorphic switch from round to filamentous morphology. This process is linked to delayed mitotic progression. Prior research has shown that Ras2 activates PKA and MAPK pathways, which are involved in this morphological change. Yet, the specific role of Swe1 and Cks1 in this context is not fully understood. No prior work had resolved how these regulatory components interact during filamentation. This gap motivated the current investigation into how morphogenesis signaling influences cell cycle regulation. The study aimed to clarify the interplay between Ras2, Swe1, and Cks1 in controlling Cdc28 activity.

This study aimed to determine how morphogenesis signaling influences cell cycle regulation through cyclin-dependent kinase (Cdc28). The researchers focused on yeast dimorphism and its impact on mitotic progression. They sought to clarify the role of Swe1 and Cks1 in modulating Cdc28 activity during filamentous growth. The study also aimed to identify the signaling pathways involved in this process. By using temperature-sensitive cdc28 mutants, the team examined how morphogenesis affects CDK regulation. The goal was to understand how Ras2 signaling interacts with Swe1 and Cks1 to control Cdc28. The researchers hypothesized that Ras2-mediated PKA signaling plays a key role in this regulation. This approach allowed them to explore the dynamic balance between morphogenesis and cell cycle timing.

The researchers used temperature-sensitive cdc28 mutants that exhibit constitutive filamentation. These mutants were subjected to epistasis analyses with RAS2 signaling effectors. The study focused on Swe1 and Cks1, two CDK regulatory components. The team examined the phosphorylation of Cdc28 by Swe1 during filamentous growth. They tested whether Ras2 activates PKA or Kss1-MAPK pathways to influence Swe1 activity. The study also assessed the role of Cks1 in CDK regulation. By comparing signaling outcomes in different mutant strains, the researchers identified pathway dependencies. This approach allowed them to dissect the interplay between morphogenesis and cell cycle control.

The study found that Swe1-mediated tyrosine phosphorylation of Cdc28 during filamentous growth is partially regulated by Ras2 activation of PKA signaling. This effect was not observed in the Kss1-MAPK pathway. The researchers observed that Cks1 influences CDK regulation through multiple mechanisms. Cks1 is involved in CDK activation, transcriptional regulation, and ubiquitin-mediated proteasome degradation. The dynamic balance between Cks1 and Swe1 determines the timing of mitosis during yeast dimorphism. Ras2/cAMP-mediated PKA signaling was identified as a key regulator of this balance. The findings suggest that morphogenesis signaling directly affects CDK function. These results highlight the role of Ras2 in modulating Swe1 and Cks1 activity.

The authors propose that morphogenesis signaling influences cell cycle regulation through cyclin-dependent kinase (Cdc28). They found that Swe1-mediated phosphorylation of Cdc28 is partially regulated by Ras2-activated PKA signaling. The study suggests that Cks1 plays a role in CDK regulation through multiple mechanisms. The dynamic balance between Cks1 and Swe1 determines mitotic timing during yeast dimorphism. The researchers conclude that Ras2/cAMP-mediated PKA signaling is a key pathway in this process. These findings suggest that morphogenesis and cell cycle regulation are interconnected. The authors do not assign essentiality to any single component. Their results provide insights into how signaling pathways modulate CDK activity during dimorphic transitions.