FIG. 4.

Expression of a TCR transgene fails to abolish Vβ13 cleavages in promoter-mutant mice. (A and B) Comparison of the levels of Vβ13 SE in wild-type and promoter-mutant mice. The levels of Vβ13 SE were assayed by LM-PCR in thymocyte DNA from +/+, P13^−/−, and P13^R/R mice with or without the TCR transgene. DNA was either undiluted (undil) or serially diluted (every threefold) and then amplified. PCR products were separated on agarose gels and hybridized with an oligonucleotide probe. JAK3 was amplified as in Fig. 2B and then hybridized with an oligonucleotide probe. Numbers indicate the band intensities normalized to that of JAK3. The level of Vβ13 SE in wild-type DNA was arbitrarily defined as 1. Shown are representative data using two sets of independently isolated DNA samples of each genotype. (C) Vβ13 cleavages in TCR transgenic promoter-mutant mice are RAG1 dependent. Vβ13 SE were assayed by LM-PCR in thymocyte DNA of RAG2^−/− mice, +/+, P13^+/−, and P13^−/− mice with or without the 2C TCR transgene and 2C⁺ P13^−/− RAG1^−/− and 2C⁺ P13^+/− RAG1^−/− mice. Lanes 13 and 14 are DNA from purified DN thymocytes of 2C⁺ P13^−/− and P13^−/− mice, respectively. One set of PCR assays was carried out for 27 cycles, and the other set was carried out for 40 cycles. Shown are representative data from three experiments.