The Sp-family of transcription factors

GC-boxes and related motifs are frequently occurring DNA-elements present i n many promoters and enhancers. In contrast to other elements it was genera lly thought that the transcription factor Spl is the only factor acting thr ough these motifs. The cloning of paralogous genes of the Spl factor uncove red the existence of a small protein family consisting of Sp1, Sp2, Sp3 and Sp4. All four proteins exhibit very similar structural features. They cont ain a highly conserved DNA-binding domain composed of three zinc fingers cl ose the C-terminus and serine/threonine- and glutamine-rich domains in thei r N-terminal regions. The high degree of structural conservation between th ese four proteins suggested that they do exert similar functions. Molecular , genetic and biochemical analyses, however, demonstrated that Sp2, Sp3 and Sp4 are not simply functional equivalents of Spl. Here, I will summarize a nd discuss recent advances which have been made towards understanding the m ode of action and biological function of individual family members. (C) 199 9 Elsevier Science B.V. All rights reserved.