Cyclin B is a protein that normally serves as a cell-cycle checkpoint protein. In cancer cells, what post-translational change to cyclin B alters its function and lets cells bypass checkpoints?

1. Cyclin B is a protein that controls progression of a cell through the cell cycle and serves as a checkpoint protein. 2. In cancer, increased phosphorylation of cyclin B is one example of a modification that alters the growth rate. 3. This phosphorylation, a post-translational event, alters cyclin B's function and prevents it from properly controlling the cell cycle. 4. As a result, cells can progress through the cell cycle unimpeded even if mutations exist that should halt growth. 5. Complete removal of the protein and DNA methylation of its gene are different mechanisms from the phosphorylation change described here. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 16 "Gene Expression", section 16.7 Cancer and Gene Regulation_