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Fig. 3. HOXA13 activates transcription from the Bmp2 and Bmp7
enhancer regions, and associates with these enhancers in vivo. Co-transfection
of NG108-15 cells with luciferase reporter plasmids containing forward or
reverse orientations of the Bmp2 enhancer sequence (A,C), or the
Bmp7 enhancer sequence (B,C), and pCMV-A13 resulted in 2.5- and
1.8-fold (Bmp2), and 1.8- and 2.0-fold (Bmp7), increases in
RLA, when compared with identical transfections with the control pCMV vector.
Luciferase activity was normalized for transfection efficiency using a Renilla
Luciferase control plasmid in all co-transfection assays. Bars represent the
standard deviation of results derived from four transfection assays. (D)
Western blot analysis of protein lysates derived from Hoxa13
wild-type (+/+), heterozygous mutant (+/) and homozygous mutant
(/) tissues confirms that the Hoxa13 antibody
recognizes proteins of the correct molecular weight for wild-type HOXA13 (43
kDa) and mutant HOXA13-GFP (64 kDa). (E) The Hoxa13 antibody
immunoprecipitates HA-tagged full-length HOXA13. (F-I) Immunostaining of
cultured limb mesenchyme from HOXA13-GFP mutant mice, using the
Hoxa13 antibody, reveals strong nuclear co-localization (H, yellow,
arrows) between the endogenous HOXA13-GFP protein (F) and the Hoxa13
antibody (G,H). Nuclei are stained with DAPI (I). (J-L) Chromatin
immunoprecipitation using the Hoxa13 antibody confirms that wild-type
(+/+) HOXA13 binds the Bmp2 (J) and Bmp7s1 (K) enhancer
regions in the developing limb, whereas immunoprecipitates from mutant limbs
(/) lacking the HOXA13 DNA-binding domain did not contain the
Bmp2 and Bmp7s1 enhancer regions. (L) The absence of
Bmp7s2 sequences in wild-type immunoprecipitates confirms HOXA13
specificity for the TAAT-containing sequences in Bmp2 and
Bmp7s1. The TAAT-containing sequences present in the Bmp2,
Bmp7s1 and Bmp7s2 regions are listed below panels J, K, and L.
NC, negative PCR control; PC, positive PCR control.