FIG. 4.
Protein synthesis is required for destabilization of coreceptor RNAs in signaled DP thymocytes. Purified DP thymocytes from B6 (left panel) and CD8.1α-transgenic (Tg) (right panel) mice were placed in signaling cultures for 7 h with either medium or TCR- and CD2-specific plate-bound MAbs. Where indicated, the culture also contained the protein synthesis inhibitor CHX (10 μg/ml). Total RNA from harvested cells was subjected to Northern blot analysis with the indicated probes. The number under each lane indicates the relative amount of RNA encoding the indicated protein quantitated by densitometry and expressed in arbitrary units normalized to the value for 18S rRNA. The amount of 18S rRNA was unchanged by culture under these conditions. Endogenously encoded CD8.2α mRNA and transgene-encoded CD8.1α mRNA were of different sizes and so could be distinguished from one another.