Specific protein 1 (Sp1) is a transcription regulator that has a transactivation domain at the N-terminus and a DNA-binding domain at the C-terminus, that contain three zinc fingers (ZF). This transcription factor selectively binds to the hexanucleotide sequence, GGGCGG (GC-box). It belongs to transcription factor family and is located on human chromosome 12q13.
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Sp1 was first detected in HeLa cells on the basis of its ability to activate the SV40 early promoter transcription. Subsequently it was shown to recognize and bind selectively to a GC-rich consensus sequence (GC-box: GGGCGG or CACCC) that presents in the promoter of several important cellular genes, including SV40 early, HIV-1, PDGF-B etc. Sp1 was the first transcription factor to be cloned. Analysis of structure and function has revealed that Sp1 can be separated into discrete functional domains. The DNA-binding domain consists of three zinc fingers that specifically bind to the GC-box element. Sp1 contains at least four separate transcriptional activation domains. Two of these domains are glutamine-rich, a well-characterized motif found in several other transcription factors. In addition to transcription, Sp1 function has been linked to cell growth, cancer, Huntington disease and other disorders through transcriptional regulation or specific protein-protein interactions. The function of Sp1 can be regulated by phosphorylation and glycosylation.
Specific protein 1 (Sp1) controls the up- and down-regulation of hCtr1 (human high-affinity copper transporter 1). It controls the expression of several genes that participates in differentiation, cell cycle and oncogenesis.It has the ability to bind GC/GT-rich promoter elements with the help of C(2)H(2)-type zinc fingers at the C-terminal domains.