Transposition of two different intracisternal A particle elements into an immunoglobulin kappa-chain gene.

Abstract

Each of two severely defective mouse K-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 LAP RNA.Transposable elements were first genetically identified in maize by McClintock because of their ability to affect gene expression and induce a multitude of chromosomal aberrations (34). Subsequently, transposable elements have been found in a variety of procaryotic and eucaryotic organisms (for reviews see reference 45), and it is now assumed that they are ubiquitous.Intracisternal A particles (IAPs) are retrovirus-like entities that are present in many embryonic and transformed cells of Mus musculus (3,4,7,12,57). Similar to retroviruses, IAPs contain a high-molecular-weight RNA species (30, 38) and a reverse transcriptase-like activity (56,59). However, unlike retroviruses, IAPs have no known extracellular phase (12,36). Approximately 1,000 DNA sequences homologous to IAP RNA (IAP elements) are scattered throughout the mouse genome (28,29). Like many of the repeated sequences in lower eucaryotes (41, 42), mouse IAP elements have a gross structural organization similar to that of the proviral forms of vertebrate retroviruses (10,26,54). Recently, transpositions of IAP elements have been observed in several transformed mouse cells (6, 9, 48) and in some cell lines derived from them (17). Because the cells in which the transpositions occurred contain IAPs, a reverse transcription mode of transposition of IAP elements is suggested.We first discovered the transposition of IAP sequences during the analysis of two mutant mouse hybridoma cell lines that were selected on the basis of defective expression of their immunoglobulin kappa (K)-chain genes (24). Characterization of molecular clones of portions of the K-chain genes from these mutant hybridomas revealed that each gene contained IAP sequences within one of its introns (17). We cloned the regions spanning both of these loci. Different IAP elements have inserted into the two K-chain genes. Here we present the nucleotide sequences at the junctions of both insertion sites and at the termini of one IAP element. These studies demonstrate that, although IAP elements resemble retroviral proviruses in many respects, they differ from provir...

Intracisternal A-type particle-mediated activations of cytokine genes in a murine myelomonocytic leukemia: generation of functional cytokine mRNAs by retroviral splicing events.

“…Transposition of IAP sequences are well documented in the literature, such sequences ranging in length from isolated LTRs (10) to full-length 7.2-kb IAP proviral sequences (20). Such examples may involve stable alterations to the germ line DNA, transmitted vertically in the context of activated (5) or disrupted and inactivated (20,32) cellular genes.…”

“…Such examples may involve stable alterations to the germ line DNA, transmitted vertically in the context of activated (5) or disrupted and inactivated (20,32) cellular genes. Non-germ line IAP transpositions may be detected by virtue of subsequent alterations of cell growth and neoplastic transformation.…”

Identification of a Novel Posttranscriptional Regulatory Element by Using a rev- and RRE-Mutated Human Immunodeficiency Virus Type 1 DNA Proviral Clone as a Molecular Trap

“…IAP proviral elements can act as endogenous mutagens by transposition to new locations in the genome, both at the somatic cell (8,20,24,40,43) and germ line levels (7). Transposition of IAP elements is occasionally associated with cellular transformation because they can activate the genes located near the transposition site (2,3,8,11,38,71).…”

Activation of the mouse mdr3 gene by insertion of retroviruses in multidrug-resistant P388 tumor cells.

“…Integration of this element in the vicinity of certain genes was found to up-or downregulate their normal level or pattern of expression. LAP integrated in the K light-chain immunoglobulin gene disrupted the expression of that gene (32), whereas IAPs integrated upstream or downstream of c-mos (16), hox-2.4 (5), or the interleukin-3 (1, 78) or interleukin-6 (4) gene caused the overexpression of these genes either by transcriptional activation (4,5,16,78) or by stabilization of the gene transcript (1). In vitro studies have clearly established that the promoters of some IAPs can be bidirectional, working in both the sense and antisense orientations, whereas promoters of other IAPs work only in the sense orientation (12).…”