TRANSCRIPTIONAL REGULATION BY THE SP FAMILY PROTEINS

Sp1 is one of the very first cellular transcription factors to be iden tified and cloned in virtue of its binding to a G-rich motif in the SV 40 early promoter, Spl protein binds to the G-rich sequences present i n a variety of cellular and viral promoters and stimulates their trans criptional activity. Recently, a number of other GC and/or GT box-bind ing factors homologous to Spl have been isolated, namely Sp2, Sp3 and Sp4, and the two more distantly related factors, BTEB and BTEB2, The d iscovery of this family highlights a previously unknown level of compl exity of transcriptional regulation of promoters containing GC and/or GT box motifs, This review focuses primarily on strategies aimed to el ucidate the transcription properties of the Spl-like factors and discu sses the experimental problems inherent in the attempt to define their respective functions. (C) 1997 Elsevier Science Ltd. All rights reser ved.