the proper differentiation of T-cells in the thymus. The long c- terminal is responsible for thymic differentiation. Role in cancer ERK3/MAPK6 interacts with and phosphorylated steroid receptor coactivator 3 (SRC-3) This coreceptor is an oncogenic protein which when overexpressed at serine 857 leads to cancer. After the phosphorylation of SRC-3 results in the upregulation of MMP activity ERK3-mediated phosphorylation at S857 was essential for interaction of SRC-3 with the ETS transcription factor PEA3, which promotes upregulation of MMP gene expression and proinvasive activity. References Further reading External links MAP Kinase Resource . EC 2.7.11