The mitogen-activated protein kinases, ERK1 and ERK2.

The MAP kinases are ubiquitous enzymes that are activated in a complex fashion and inactivated by multiple phosphatases including a dedicated dual specificity enzyme. These kinases have a diverse array of substrates with important functions that result in their substantial regulatory impact. The ERK/MAP kinase cascade displays not only downstream but also upstream interactions as well as cross talk with other signaling pathways which fine tunes the cascade in a cell type-specific fashion. Transforming agents utilize this cascade in inducing cell proliferation.