Molecular cloning of a human homologue of Drosophila heterochromatin protein HP1 using anti-centromere autoantibodies with anti-chromo specificity.
We have identified a novel autoantibody specificity in scleroderma that we term anti-chromo. These antibodies recognize several chromosomal antigens with apparent molecular mass of between 23 and 25 kDa, as determined by immunoblots. Anti-chromo autoantibodies occur in 10-15% of sera from patients with anti-centromere antibodies (ACA). We used anti-chromo antibodies to screen a human expression library and obtained cDNA clones encoding a 25 kDa chromosomal autoantigen. DNA sequence analysis reveals this protein to be a human homologue of HP1, a heterochromatin protein of Drosophila melanogaster. We designate our cloned protein HP1Hs alpha. Epitope mapping experiments using both human and Drosophila HP1 reveal that anti-chromo antibodies target a region at the amino terminus of the protein. This region contains a conserved motif, the chromo domain (or HP1/Pc box), first recognized by comparison of Drosophila HP1 with the Polycomb gene product. Both proteins are thought to play a role in creating chromatin structures in which gene expression is suppressed. Anti-chromo thus defines a novel type of autoantibody that recognizes a conserved structural motif found on a number of chromosomal proteins.
Department of Cell Biology and Anatomy, Johns Hopkins School of Medicine, MD 21205.
W S
WS
Saunders
C
C
Chue
M
M
Goebl
C
C
Craig
R F
RF
Clark
J A
JA
Powers
J C
JC
Eissenberg
S C
SC
Elgin
N F
NF
Rothfield
W C
WC
Earnshaw
D000595:Amino Acid Sequence; D000818:Animals; D000974:Antibodies, Antinuclear / Q000276:immunology; D001483:Base Sequence; D002503:Centromere / Q000737:chemistry*; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000096:biosynthesis* / Q000737:chemistry / Q000276:immunology; D003001:Cloning, Molecular; D017124:Conserved Sequence; D004331:Drosophila melanogaster / Q000235:genetics; D006367:HeLa Cells; D006570:Heterochromatin / Q000737:chemistry*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011994:Recombinant Proteins / Q000096:biosynthesis* / Q000276:immunology; D012595:Scleroderma, Systemic / Q000276:immunology; D017386:Sequence Homology, Amino Acid
D000974:Antibodies, Antinuclear; D002868:Chromosomal Proteins, Non-Histone; D006570:Heterochromatin; D011994:Recombinant Proteins; D000090266:Chromobox Protein Homolog 5