A tale of three fingers: the family of mammalian Sp/XKLF transcription factors

One of the most common regulatory elements is the GC box and the related GT /CACC box, which are widely distributed in promoters, enhancers and locus c ontrol regions of housekeeping as well as tissue-specific genes, For long i t was generally thought that Sp1 is the major factor acting through these m otifs, Recent discoveries have shown that Sp1 is only one of many transcrip tion factors binding and acting through these elements. Sp1 simply represen ts the first identified and cloned protein of a family of transcription fac tors characterised by a highly conserved DNA-binding domain consisting of t hree zinc fingers. Currently this new family of transcription factors has a t least 16 different mammalian members, Here, we will summarise and discuss recent advances that have been directed towards understanding the biologic al role of these proteins.