The 72/74-kDa polypeptides of the 70-110 S large heterogeneous nuclear ribonucleoprotein complex (LH-nRNP) represent a discrete subset of the hnRNP M protein family.
Pre-mRNA processing in eukaryotes is thought to take place on a multitude of nuclear ribonucleoprotein (RNP) complexes, the most abundant of them being the heterogeneous nuclear (hn) RNP complexes. The identification in mammalian nuclear extracts of a novel, less-abundant 70-110 S heterogeneous RNP, named large heterogeneous nuclear RNP (LH-nRNP), has previously been reported by Aidinis, Sekeris and Guialis (1995) Nucleic Acids Res. 23, 2742-2753. The structural composition of the LH-nRNP complex has been determined following the production of polyclonal antibodies against the major protein constituents of the complex, the pair of the 72/74-kDa polypeptides. In the present study evidence is shown to prove that the 72/74-kDa proteins are members of the hnRNP M protein family, hereafter referred to as 72/74(M) polypeptides. The extensive application of two-dimensional gel electrophoresis, combined with specific immunoprecipitation and immunoblotting assays, has allowed the assignment of the 72/74(M) proteins to a subset of the hnRNP M family, characteristic of the presence of the LH-nRNP complex and distinct from the hnRNP-associated M1-M4 components. Moreover, the immunoselection of the LH-nRNP complex from [(32)P]orthophosphate-labelled HeLa cells, with the parallel application of UV irradiation, has permitted the identification of the 72/74(M) polypeptides as the sole protein constituents of the complex in direct contact with the RNA. It is proposed that LH-nRNP constitutes a discrete subset of hnRNP complexes, having a possible role in establishing specific interactions between hnRNP and nuclear-matrix protein components.
Kafasla
P
P
Laboratory of Molecular Biology, Institute of Biological Research and Biotechnology, The National Hellenic Research Foundation, 48 Vas. Constantinou Avenue, Athens 11635, Greece.
Patrinou-Georgoula
M
M
Guialis
A
A
D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D008969:Molecular Sequence Data; D005810:Multigene Family; D010455:Peptides / Q000737:chemistry; D011233:Precipitin Tests; D051381:Rats; D012261:Ribonucleoproteins / Q000737:chemistry* / Q000145:classification / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D014466:Ultraviolet Rays
D010455:Peptides; D012261:Ribonucleoproteins