Nucleic Acids Research Advance Access originally published online on December 10, 2007
Nucleic Acids Research 2008 36(2):648-665; doi:10.1093/nar/gkm1045
Nucleic Acids Research, 2008, Vol. 36, No. 2 648-665
© 2007 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Molecular Biology |
Functional endogenous LINE-1 retrotransposons are expressed and mobilized in rat chloroleukemia cells
1Max-Planck-Institut für Zellbiologie, Rosenhof, D-68526 Ladenburg and 2Paul-Ehrlich-Institut, Section PR2/Retroelements, Paul-Ehrlich-Strasse 51-59, D-63225 Langen, Germany
*To whom correspondence should be addressed. Tel: +49 6103 773 105; Fax: +49 6103 771 265; Email: schgr{at}pei.de Correspondence may also be addressed to Peter Traub. Tel: +49 228 739 573; Fax: +49 228 739 004; Email: p.traub{at}uni-bonn.de; Genrich V. Tolstonog. Tel: +49 4048 051 235; Fax: +49 4048 051 117; Email: genrich.tolstonog{at}hpi.uni-hamburg.de
Received March 24, 2007. Revised November 1, 2007. Accepted November 2, 2007.
LINE-1 (L1) is a highly successful autonomous non-LTR retrotransposon and a major force shaping mammalian genomes. Although there are about 600 000 L1 copies covering 23% of the rat genome, full-length rat L1s (L1Rn) with intact open reading frames (ORFs) representing functional master copies for retrotransposition have not been identified yet. In conjunction with studies to elucidate the role of L1 retrotransposons in tumorigenesis, we isolated and characterized 10 different cDNAs from transcribed full-length L1Rn elements in rat chloroleukemia (RCL) cells, each encoding intact ORF1 proteins (ORF1p). We identified the first functional L1Rn retrotransposon from this pool of cDNAs, determined its activity in HeLa cells and in the RCL cell line the cDNAs originated from and demonstrate that it is mobilized in the tumor cell line in which it is expressed. Furthermore, we generated monoclonal antibodies directed against L1Rn ORF1 and ORF2-encoded recombinant proteins, analyzed the expression of L1-encoded proteins and found ORF1p predominantly in the nucleus. Our results support the hypothesis that the reported explosive amplification of genomic L1Rn sequences after their transcriptional activation in RCL cells is based on L1 retrotransposition. Therefore, L1 activity might be one cause for genomic instability observed during the progression of leukemia.
Present addresses: Alexander Kirilyuk, Georgetown University, Lombardi Cancer Center, Washington, DC 20007, USA. Genrich V. Tolstonog, Heinrich-Pette Institut für Experimentelle Virologie und Immunologie an der Universität Hamburg, D-20251 Hamburg, Germany. Peter Traub, Institut für Zelluläre und Molekulare Botanik, Universität Bonn, D-53115 Bonn, Germany.
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors.