Four And A Half LIM Domains Protein 5 (FHL5)

FHL5 is coordinately expressed with activator of cAMP-responsive element modulator (CREM). It is associated with CREM and confers a powerful transcriptional activation function. CREM acts as a transcription factor essential for the differentiation of spermatids into mature spermatozoa. There are multiple polyadenylation sites found in this gene.

The LIM domain is a cysteine-rich, double-zinc finger structural motif involved in protein-protein interactions. Act bypasses the classic requirements for CREM activation, namely phosphorylation of ser117 and interaction with CREB-binding protein (CREBBP). Northern blot analysis revealed that expression of Act is restricted to testis. Western blot analysis determined that Act colocalizes in purified spermatids with CREM.