Transcription of protein coding genes in metazoans involves the concerted action 
of enhancer binding proteins and the RNA polymerase II apparatus. The cross talk 
between these two classes of transcription factors is mediated by an elaborate 
set of cofactor complexes. For the activation of transcription by the promoter 
specificity protein 1 (Sp1), TATA binding protein-associated factors in the 
TFIID complex originally were identified as necessary coactivators, but the 
identity of additional cofactors required for activated transcription was 
unknown. Recently, we have reported the isolation and properties of a cofactor 
complex, CRSP (cofactor required for Sp1), which functions in conjunction with 
the TATA binding protein-associated factors to promote efficient activation of 
transcription by Sp1. CRSP contains unique subunits as well as polypeptides that 
are shared with other cofactor complexes. Here, we report a detailed 
purification protocol for the isolation of CRSP from human HeLa cells. Our 
purification strategy takes advantage of the ability of CRSP to bind 
Ni2+-nitrilotriacetic acid-agarose resin as well as other conventional 
chromatographic resins. We also describe a streamlined purification protocol 
that allows a more rapid and efficient means to isolate active CRSP.