FIG. 4.

Germ line expression of TCRβ miniloci correlates with DβJβ recombination. Total cellular RNAs were harvested from individual transfectants maintained in the presence (without tTAk) or absence (with tTAk) of tetracycline (TET) for 3 days. The resultant RNAs were subjected to RT-PCR amplification with primers C and D (Fig. 1), and the reaction products were analyzed by Southern blotting using an oligonucleotide probe derived from Jβ1 coding sequences (top panel). The relative positions of amplification products corresponding to germ line transcripts that were processed at either Jβ1 (DβJβ1Cμ) or Jβ2 (DβJβ2Cμ) 3′ splice sites are shown at the left. Total cDNA levels were controlled in each sample by using a PCR assay specific for β-actin transcripts (bottom panel). The linearity of each assay was confirmed with serial dilutions of cDNA (lanes 21 to 26) derived from the 5′Dβ/iEκ transfectant shown in lane 1.