Unusual expression of LINE-1 transposable element in the MRL autoimmune lymphoproliferative syndrome-prone strain.
LINE-1 are endogenous mobile genetic elements that have dispersed and accumulated in the genomes of eukaryotes via germline transposition, with up to 100,000 copies in mammalian genomes. LINE-1 elements transpose by reverse transcription of their own transcript. Transposition requires synthesis of a full-length, sense-strand transcripts and proteins encoded by open reading frame (ORF) 1 and ORF2. Although severely repressed in most normal tissues, LINE-1 occasionally leads to disease by insertional mutagenesis. In the present study, Northern blot and in situ hybridization analyses revealed a template-strand transcription of LINE-1 ORF2 (encoding reverse transcriptase, RT) in lymphoid organs and the liver from MRL-+/+ and Fas-deficient MRL/lpr strains and their normal ancestors. While these sense transcripts are restricted to the nucleus in hepatocytes, they are also found in the cytoplasm in splenocytes. In contrast to transcription, ORF2 translation was detected only in MRL strains, as shown by the cytoplasmic labelling of splenic cells obtained with a monoclonal antibody recognizing the LINE-1 RT. This antibody coprecipitated two proteins of 45 and 12 kDa from MRL/lpr lymphoid organ lysates that were removed by pretreatment with anti-beta2-microglobulin antiserum, suggesting a structural association between a LINE-1 product and a major histocompatibility complex class I or class I-like molecule.
Benihoud
Karim
K
INSERM U 267, 14, avenue Paul-Vaillant-Couturier, 94807 Villejuif, France.
Bonardelle
Danielle
D
Soual-Hoebeke
Emmanuelle
E
Durand-Gasselin
Ingrid
I
Emilie
Dominique
D
Kiger
Nicole
N
Bobé
Pierre
P
D000818:Animals; D001327:Autoimmune Diseases / Q000235:genetics* / Q000378:metabolism; D015152:Blotting, Northern; D002213:Capsid / Q000235:genetics / Q000378:metabolism; D036022:Capsid Proteins; D004251:DNA Transposable Elements; D000939:Epitopes / Q000235:genetics; D015870:Gene Expression; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D007124:Immunoenzyme Techniques; D008099:Liver / Q000378:metabolism; D020084:Long Interspersed Nucleotide Elements / Q000235:genetics*; D008221:Lymphoid Tissue / Q000378:metabolism; D008232:Lymphoproliferative Disorders / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008806:Mice, Inbred AKR; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008811:Mice, Inbred DBA; D019463:Mice, Inbred MRL lpr; D012333:RNA, Messenger / Q000378:metabolism; D013154:Spleen / Q000378:metabolism
D036022:Capsid Proteins; D004251:DNA Transposable Elements; D000939:Epitopes; D006023:Glycoproteins; D015395:Histocompatibility Antigens Class I; D012333:RNA, Messenger