ELF1 belongs to the ETS family. It is a transcription factor that activates the LYN and BLK promoters. ELF1 appears to be required for the T-cell-receptor-mediated trans activation of HIV-2 gene expression. It binds specifically to two purine-rich motifs in the HIV-2 enhancer. ELF1 has a repellent axon guidance function for temporal, but apparently not for nasal, axons. The antibody is specific to ELF1.