Interaction between HSI,II and the activated hGH-N promoter is HSI dependent and pituitary specific. (A) The BglII map of the hGH/P1 transgene. Each BglII site is indicted below the locus map by a tick mark. The position of each of the PCR primers is also shown (arrowheads); the GH/CS primer, common to all four GH-related genes (large arrowheads), functioned as the anchor primer in these studies. The four upstream primers detect individual BglII fragments that contain HSV, p4, HSII, CD79b or p1 regions. (B) Summary of the 3C analyses in hGH/P1(TerF) pituitary (Pit) chromatin. 3C assays were performed on pituitaries (black bars) or livers (white bars) of mice representing two hGH/P1 transgenic lines and on pituitaries of mice representing two hGH/P1(ΔHSI) lines (grey bars). GH/CS, the anchor primer for these studies, was paired with each of the four 5′ primers in the PCR analysis of the ligation products. The panels below the histogram show representative ethidium bromide-stained agarose gels containing the indicated PCR amplification products; the distinct bands representing the hGH-N- and hGH-V/hCS-specific ligation products are indicated by arrowheads at the left of the top panel. The intensities of the bands were quantified. Lane C (control) contains the PCR amplifications of the ligation products of a BglII-digested hGH/P1 plasmid DNA. Lane marked − contains the products of the assay performed using the hGH/P1 pituitary chromatin preparation in the absence of T4 DNA ligase. The band in the CD79b (−) sample represents a background amplification product that is insensitive to BglII. The histogram values represent ratios of the signal of the hGH-N-specific ligation product to the combined placental gene-specific ligation products (supplementary Figs 1,2 online). Each histogram bar represents the mean±s.d. of four or more independent studies on each of the two transgenic lines. In comparison of the value obtained from hGH/P1 pituitary chromatin to the indicated value, a single asterisk indicates P<0.01 and a double asterisk indicates P<0.001. 3C, chromosome conformation capture; hGH, human growth hormone; LCR, locus control region.