Isolation and characterization of cDNA encoding the antigenic protein of the human tRNP(Ser)Sec complex recognized by autoantibodies from patients withtype-1 autoimmune hepatitis.
We previously described autoantibodies against a UGA serine tRNA-protein complex (tRNP(Ser)Sec) in patients with type-1 autoimmune hepatitis [1] and now define the specificity and frequency of this autoantibody and the DNA sequence encoding the tRNA(Ser)Sec-associated antigenic protein. The presence of anti-tRNP(Ser)Sec antibodies was highly specific for type-1 autoimmune hepatitis, as 47.5% of patients were positive compared with none of the control subjects. To characterize the antigenic protein(s), we immunoscreened a human cDNA library with anti-tRNP(Ser)Sec-positive sera. Two clones (19 and 13) were isolated. Clone 19 encodes a protein with a predicted molecular mass of 48.8 kD. Clone 13 is a shorter cDNA, almost identical to clone 19, which encodes a 35.9-kD protein. Expression of both cDNAs was accomplished in Escherichia coli as His-tagged recombinant proteins. Antibodies eluted from both purified recombinant proteins were able to immunoprecipitate the tRNA(Ser)Sec from a HeLa S3 cell extract, demonstrating their cross-reactivity with the mammalian antigenic complex. Recent cloning data relating to the target antigen(s) of autoantibodies in autoimmune hepatitis patients that react with a soluble liver antigen (SLA) and a liver-pancreas antigen (LP) have revealed that these two autoantibodies are identical and that the cloned antigen shows 99% amino acid sequence homology with tRNP(Ser)Sec.
Costa
M
M
Department of Immunology, Sant Pau Hospital, Barcelona, Spain, and Department of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN, USA.
Rodríguez-Sánchez
J L
JL
Czaja
A J
AJ
Gelpí
C
C
D000293:Adolescent; D000328:Adult; D000368:Aged; D000595:Amino Acid Sequence; D000918:Antibody Specificity; D001323:Autoantibodies / Q000276:immunology*; D001324:Autoantigens / Q000235:genetics* / Q000276:immunology; D001327:Autoimmune Diseases / Q000276:immunology*; D001483:Base Sequence; D015153:Blotting, Western; D018076:DNA, Complementary / Q000235:genetics* / Q000302:isolation & purification; D005796:Genes; D016153:Genes, Suppressor; D006367:HeLa Cells / Q000737:chemistry; D019693:Hepatitis, Autoimmune / Q000276:immunology*; D006801:Humans; D008099:Liver / Q000276:immunology; D008107:Liver Diseases / Q000276:immunology; D046911:Macromolecular Substances; D008875:Middle Aged; D008969:Molecular Sequence Data; D010179:Pancreas / Q000276:immunology; D012333:RNA, Messenger / Q000235:genetics*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000276:immunology; D012680:Sensitivity and Specificity
D001323:Autoantibodies; D001324:Autoantigens; D018076:DNA, Complementary; D046911:Macromolecular Substances; D012333:RNA, Messenger; D012346:RNA, Transfer, Amino Acyl; D011993:Recombinant Fusion Proteins; C112705:selenocysteinyl-tRNA