RT extension of tRNAs NC-annealed to complementary and noncomplementary PBS sequences using the HIV-1 HXB2 template. (A) Agarose gel (2%) showing PCR-amplified primer extension products. The tRNA primers were extended by 400 nM RT. The presence (+) or absence (−) of a tRNA primer in the reactions is indicated. PCR-negative controls were carried out with the DNA primers specific for the tRNALys-3-primed product (lanes 11) or the tRNAPro-primed product (lane 12). The RNA templates used contain a PBS complementary to either human tRNALys-3 (Lys) or human tRNAPro (Pro). In addition to a Pro-PBS, the Tag-Pro template contains a 4-nt signature tag near the 5′ end. (B) DNA sequences of PCR products obtained in A. Sets 1–4b, the portion of each ladder shown includes the nucleotide sequence of the tRNA primer and the PBS (nucleotides explicitly shown). The choice of sequencing primer resulted in obtaining the sense and antisense sequence of the RNA template and tRNA primer, respectively. The small arrow indicates the 5′ end of the tRNA sequence. Set 4c, sequence information to confirm the presence of the signature tag in the PCR product obtained from RT extension of tRNALys-3 annealed onto the Pro-PBS (A, lane 9). The inserted sequence (5′-AATT-3′) is italicized.