ALTERNATE NAMES :
protein, X chromosome
Heterogenous nuclear ribonucleoprotein G
RNA-binding motif protein, X chromosome
RBM has an ancient X-chromosome homologue called hnRNPG (also called RBMX). hnRNPG is expressed in all cells. Our hypothesis
is that RBM might have become specialised to fulfil a special function in germ cells, while hnRNPG may play a somewhat similar
role in other cells in the body. We are trying to using various approaches to address this function.
The University of Newcastle, Institute of Human Genetics
Autoimmune antibodies to hnRNPG protein in dogs with systemic lupus erythematosus: epitope mapping of the
Soulard M, Della Valle V, Larsen CJ.
Centre de Biologie Veterinaire de
l'Arche, 110 rue Jean Jaures, 92800, Puteaux, France.
We previously reported the presence of circulating autoantibodies
to hnRNPG protein in dogs with systemic lupus erythematosus (Soulard et al. 1993, 1994). These antibodies appeared to be specifically
limited to German shepherd dog species. In the present report, we have analysed the nature of the hnRNPG epitopes responsible
for autoantibody specificity. By using a set of 11 dog sera selected for their strong reactivity to hnRNPG protein, we have
found that these sera had the ability to recognize two epitopes: (1) within a stretch of 33 amino acids located around the
central part of protein, that is readily detected by immunoblotting; (2) a N-terminal conformation of the protein close to
the RNA binding domain (RBD), that is revealed by immunoprecipitation. Our data strongly support the notion that the dog autoimmune
response against hnRNPG protein is antigen-driven.
A large set of proteins has been identified that binds to pre-mRNA.These proteins have been named hnRNP proteins (hnRNA
is a historic name for RNA in the cell nucleus, much of which is pre-mRNA). Several different hnRNP-proteins bind to the
same pre-mRNA immediately as the RNA is transcribed and an RNA-protein complex is formed.
Many of the hnRNP proteins share the same type of RNA binding domain. This concensus RNA binding domain can also be
found in many other proteins that interact with mRNA, or other kinds of RNA. There are also other types of RNA binding domains
found in other hnRNP proteins.
The hnRNP proteins presumably have several different functions, but these are not well known yet. It has been assumed
that hnRNP proteins help package the pre-mRNA into functional complexes. For example, hnRNP proteins may be involved in
presenting the pre-mRNA to the splicing machinery. It is known that hnRNP A1 protein can influence the choice of splice
sites in pre-mRNA. Three hnRNP-proteins have been shown to be involved in the transport of mRNA to the cytoplasm. The hnRNP
C protein contains a retention sequence that appears to prevent mRNA from being transported out of the nucleus and hnRNP
A1 and hnRNP K each contain an export signal as part of their amino acid chain.
It is further possible that hnRNP proteins play a role also in the cytoplasm. The hnRNP A1 protein has been shown to
accompany the mRNA into the cytoplasm and is present during translation.