References
Negative feedback: MAPK1/ERK2 phosphorylates RAF1 on Ser 29, 43, 289, 296, 301, 642, generating an inactive kinase.
PIN1, a prolyl isomerase converts pSer and pThr residues from the cis to the trans conformation, which is preferentially recognized and dephosphorylated by PPP2R1A.