Molecular definition and sequence motifs of the 52-kD component of human SS-A/Ro autoantigen.

Abstract

Serum SS-A/Ro autoantibodies are commonly found in patients with Sjogren's syndrome, systemic lupus erythematosus, neonatal lupus, and subacute cutaneous lupus. Two proteins of 60 and 52 kD have been described as targets for these autoantibodies. To define the 52-kD component unambiguously, cDNA clones were isolated from buman HepG2 and MOLT4 cell cDNA libraries. The identity of cDNA was established by (a) the specificity of the antibody affinity purified from the recombinant protein, (b) the reactivity of the purified recombinant protein with prototype SS-A/Ro sera in immunoblot and ELISA, and (c) two-dimensional gel comigration of MOLT-4 cell 52-kD protein and the recombinant protein. A 1.9-kb cDNA encoded the complete 52-kD protein containing 475 amino acids (M, 54,082). Putative zinc-finger domains and a leucine zipper motif were identified in the amino-terminal half of the 52-kD protein, implicating its possible association with DNA/RNA. Sequence homology detected between the 52-kD protein and human ret transforming protein, and mouse T cell gene expression down-regulatory protein rpt-1, may provide leads to the functional role of the 52-kD protein in addition to the possibility that these proteins might constitute members of a subfamily of finger proteins. (J. Clin. Invest. 1991. 87:68-76.)

Identification of mothers at risk for congenital heart block and other neonatal lupus syndromes in their children. comparison of enzyme‐linked immunosorbent assay and immunoblot for measurement of anti–ss‐a/ro and anti–ss‐b/la antibodies

“…Another polypeptide in the SS-A/Ro complex, identified as a S2-kd species (1 l), is antigenically and structurally distinct from the 60-kd protein (12). The 52-kd SS-A/Ro protein has a high degree of homology with the ret finger protein, rfp, which is a cellular homolog of a human transforming protein ret and raises the question of whether the 52-kd SS-A/Ro protein might have similar transforming potential (12). Commercially available assays, including enzyme-linked immunosorbent assay (ELISA) and immunodiffusion, do not distinguish between antibodies against the 52-kd and the 60-kd SS-AIR0 antigens.…”

Characterisation of a novel cysteine/histidine‐rich metal binding domain from Xenopus nuclear factor XNF7

“…PML and T18 possess two B-box like domains which appear to form a subgrouping of the B-box family as highlighted by the presence of an extra potential cysteine metal ligand [16]. The other members of the family include RPT-I [23], SS-A/R0 [24], XNF7 [25] and PwA33 [26]. In order to understand the function of the B-box domain, both within this diverse family of proteins, and in relation to the RING finger and a-helical coiled-coil domains of the conserved tripartite motif, we have synthesised and purified a peptide corresponding to the B-box motif from the Xenopus protein XNF7.…”

Neonatal lupus syndrome: the heart as a target of the immune system

“…The 52kD polypeptide is alternatively spliced, yielding an isoform that lacks aminoacids 169-245 of the full-length protein (Chan et al 1995). Although their function is not yet known, both the 60 and the 52 kD Ro have zinc finger motifs capable of binding DNA and regulating gene expression (Chan et al 1991, Itoh et al 1991. The anti-La/SSB is another auto-antibody found in the serum of mothers and affected children.…”