Transcription factors Sp1 and Sp4 are bound in vivo to the GC-box region of P2-promoter in DRG chromatin. Composite ethidium bromide-stained agarose gel showing evidence of PCR amplified products directed by oligodeoxynucleotide primers spanning TRPV1 GC-box "a" and "b" (top) using template DNA provided as: control input chromatin DNA without immunoprecipitation (Inp), chromatin immunoprecipitated with antisera against transcription factors (Sp1) or (Sp4), chromatin immunoprecipitated with non-immune (IgG), absence of chromatin template - primers only (Pr). Plus sign (+) denotes successful amplification of expected PCR product (arrow). There was no evidence in vivo of Sp3 binding (not shown). Each lane represents 1 of at least 3 independent ChIP assays. Molecular size ladder: kilobase (kb).