Five proteins share the same structural organization and a high degree of sequence homology in this group: four and a half LIM domain protein (FHL) 1, FHL2, FHL3, FHL4, and activator of cAMP-responsive element (CRE) modulator (CREM) in testis (ACT). LIM domains are constituted by a conserved cysteine- and histidine-rich structure shaped in two repeated zinc fingers first identified in the proteins encoded by the Lin-11, Isl-1, and Mec-3 genes. The LIM domain has been shown to function as a protein