SOCS1 is a direct transcriptional target of GLI.

<p><b>A</b>) Graphical overview of the cloned SOCS1 promoter region containing 5 putative GLI binding sites. Numbers refer to the transcription start site (RefSeq NM_003745.1). Sequences of putative GLI binding sites are listed on the right. Bases differing from GLI consensus sequence are underlined. <b>B</b>) Luciferase assay of a 1822bp fragment of the human SOCS1 promoter (SOCS1prom, see A) and deletion construct SOCS1promdel (see A). HaCaT cells were co-transfected with SOCS1 reporter and GLI expression plasmids as indicated. +/-SD refers to quadruplicate samples. <b>C</b>) Chromatin immunoprecipitation shows specific binding of GLI2 to the SOCS1 promoter. Chromatin isolated from doxycycline (DOX) treated GLI2act-HaCaT cells was precipitated with either GLI2 specific antibody (αGLI2) or unspecific (normal IgG) antibody as control. Two fragments (F1 and F2) spanning BS2, BS3, and BS4 or BS5 were amplified from the SOCS1 promoter by PCR. As positive control a 148-bp fragment (PTCHprom) from the PTCH promoter was used [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075317#B49" target="_blank">49</a>] and a 284-bp fragment (RPLP0prom) from the human RPLP0 promoter served as negative control [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075317#B70" target="_blank">70</a>]. * P < 0.001.