Somatic hypermutation. Physiologic SHM targets regulatory sequences of the IgV gene and the additional GC genes, BCL6 and FAS (CD95). Aberrant SHM targets additional GC genes including PIM1, cMYC, PAX5 RhoH/TTF as well as BCL6, and, possibly, FAS. Figure modified from R. Dalla-Favera, Institute of Genetics, Columbia University, New York, NY.