string: To test whether short antisense TSSa-RNAs previously described (5) are derived from longer transcripts and to determine the structure of their 5′ termini, we used rapid amplification of 5′ complementary DNA ends (5′-RACE) to characterize divergent upstream antisense RNAs from the Isg20l1, Tcea1, Txn1, and Sf3b1 genes in V6.