Sp1 and its likes: biochemical and functional predictions for a growing family of zinc finger transcription factors.

The discovery and functional characterization of Sp1 as a GC-rich binding zinc finger protein provided a useful paradigm for understanding mechanisms mediating transcriptional activation in eukaryotic cells. This early paradigm suggested that promoters carrying GC-rich sequences are activated by Sp1 through its interaction with proteins from the basal transcriptional machinery to upregulate gene expression. Since the time of this seminal work, studies from several laboratories have led to the discovery of many Sp1-like transcription factors containing highly homologous DNA binding motifs that bind to similar sequences. Consequently, this knowledge poses many important questions regarding whether these related proteins have similar or antagonistic biochemical and functional properties to Sp1. The goal of this article is to use available database information and recent experimental evidence to describe the current repertoire of Sp1-like zinc finger transcription factors in mammalian cells. Furthermore, we discuss structural and functional studies that reveal that these proteins may share a role in morphogenetic pathways. Altogether, this information is aimed at better understanding how this growing family of transcription factors work to regulate gene expression and morphogenesis.