G2Mövergången

G2Mövergången is a term used to describe the transition from the G2 phase to mitosis in the cell cycle. This critical checkpoint ensures that the cell is properly prepared to divide, preventing errors that could lead to aneuploidy or other genetic abnormalities. The G2 phase is a period of growth and preparation for mitosis, where the cell duplicates its organelles and synthesizes proteins necessary for cell division. Before entering mitosis, the cell must pass the G2/M checkpoint.

The G2/M checkpoint is regulated by a complex network of proteins, primarily cyclin-dependent kinases (CDKs) and their regulatory subunits, cyclins. Specifically, the cyclin B-CDK1 complex plays a crucial role in triggering the transition. During the G2 phase, cyclin B levels rise, and it binds to CDK1. This complex is then activated through phosphorylation by specific kinases, such as the CAK (CDK-activating kinase). Once active, the cyclin B-CDK1 complex initiates a cascade of events that lead to the condensation of chromosomes, breakdown of the nuclear envelope, and formation of the mitotic spindle.

Errors in the G2/M transition can have severe consequences. If a cell with damaged DNA proceeds into mitosis, it can result in daughter cells with incomplete or duplicated chromosomes. This can lead to cell death or the development of diseases like cancer. Therefore, the G2/M checkpoint is tightly controlled, with mechanisms in place to halt progression if DNA damage is detected. This allows time for DNA repair before cell division. The efficient and accurate execution of the G2Mövergången is fundamental to maintaining genomic stability.