Purification of antigenically intact Ro ribonucleoproteins; biochemical and immunological evidence that the 52-kD protein is not a Ro protein

Clin Exp Immunol. 1995 Jun;100(3):489-98. doi: 10.1111/j.1365-2249.1995.tb03728.x.


Anti-Ro sera immunoprecipitate Ro ribonucleoproteins (RNPs) from human cell extracts. Ro RNPs are biochemically heterogeneous particles whose functions are unknown and whose exact composition remains controversial. In addition to 60-kD Ro and to La proteins, a 52-kD polypeptide (p52) has been proposed to be a stable component of the Ro RNPs. To confirm the immunological studies supporting this hypothesis, we have biochemically purified Ro RNPs from HeLa cells using non-denaturing conditions. Ro RNPs segregated into three distinct populations, one of which only contained hY5 RNA (RohY5 RNPs). No p52 co-purified with Ro RNPs. Despite the absence of p52, purified Ro RNPs had biochemical and immunological properties identical to those of unfractionated Ro RNPs. Many anti-Ro sera only recognize p52 in immunoblots, and are said to be monospecific anti-p52. Preincubation with purified RohY5 RNPs (free of p52) of all human anti-Ro (including so-called monospecific anti-p52) sera abolished their capacity to immunoprecipitate Ro RNPs from unfractionated HeLa cell extracts. Conversely, preincubation of anti-Ro sera with purified p52 protein specifically inhibited recognition of p52 in immunoblots, but did not interfere with immunoprecipitation of Ro RNPs. Our data demonstrate that anti-p52 antibodies do not target intact Ro RNPs, nor do they target the native 60-kD Ro protein. Contrary to previous reports, p52 protein is not a stable component of antigenically intact Ro RNPs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Autoantibodies / immunology
  • Autoantigens / chemistry*
  • Autoantigens / isolation & purification
  • Base Sequence
  • Blotting, Western
  • Cloning, Molecular
  • DNA Primers / chemistry
  • HeLa Cells
  • Humans
  • Molecular Sequence Data
  • Molecular Weight
  • Precipitin Tests
  • RNA, Small Cytoplasmic*
  • Rabbits
  • Ribonucleoproteins / chemistry*
  • Ribonucleoproteins / immunology*
  • Ribonucleoproteins / isolation & purification


  • Autoantibodies
  • Autoantigens
  • DNA Primers
  • RNA, Small Cytoplasmic
  • RO60 protein, human
  • Ribonucleoproteins
  • SS-A antigen