Transposition of Two Different Intracisternal A Particle Elements into an Immunoglobulin Kappa-Chain Gene

Abstract

Each of two severely defective mouse κ-chain genes has acquired a different intracisternal A particle (IAP) element within one of its introns. One IAP element generated 6-base-pair direct repeats upon insertion. In contrast, the other IAP element was not flanked by direct repeats and was missing a single nucleotide from its 3′ terminus. Sequence analysis of the latter IAP element demonstrated that its long terminal repeats were not identical. Nevertheless, the long terminal repeats were organized like proviral long terminal repeats, and this IAP element did contain two regions that were analogous to retroviral priming sites for RNA-directed DNA synthesis. The region that corresponded to a retroviral tRNA primer binding site was complementary to the 3′ ends of all mammalian phenylalanine tRNAs. These findings are discussed in the context of the presumed mode of transposition of IAP elements involving the reverse transcription of IAP RNA.