FIG. 1.

Generation of STAT3^fl/+ ES cells and of MX⁺ or MX⁻ STAT3^fl/fl mice. (A) The structure of the replacement targeting vector along with the structures of the wild-type, replaced, floxed, and deleted alleles, the position of the probe used, and the predicted sizes of the restriction fragments are depicted. The replaced allele was detected by Southern blotting on EcoRV-digested genomic DNA using as a probe a cDNA fragment spanning exons 15 to 24. Cre-mediated deletion was expected to generate STAT3 floxed and deleted alleles and was diagnosed by Southern blotting using the intronic probe 2.1. (B, C, and D) Southern blot analysis of genomic DNA from targeted ES cells either before (B and C) or after (D) Cre-mediated deletion. The probes used and the relevant alleles detected are indicated (wt, wild type; repl, replaced; fl, floxed; del, deleted). (E and F) Western blot of liver extracts from poly(I · C)-treated mice. MX⁺ or MX⁻ STAT3^fl/fl mice were injected once i.p. with poly(I · C) followed 4 days later by either LPS or apyrogenic saline solution. The livers from the indicated mice were collected after 4.5 and 9 h (F) or after 24 h (E), and total extracts were subjected to Western blot analysis with anti-STAT3 (E) or anti-phospho-(Tyr 705) STAT3 (P-STAT3) (F) antibodies. The blots were stripped and reprobed with anti-STAT1 (E) or anti-STAT3 (F) antibodies. C, STAT3-enriched control extract.