title: Structure of nuclear ribonucleoprotein: identification of proteins in contact with poly(A)+ heterogeneous nuclear RNA in living HeLa cells.
abstract: The processing of heterogeneous nuclear RNA into messenger RNA takes place in special nuclear ribonucleoprotein particles known as hnRNP. We report here the identification of proteins tightly complexed with poly(A)+ hnRNA in intact HeLa cells, as revealed by a novel in situ RNA-protein cross-linking technique. The set of cross-linked proteins includes the A, B, and C "core" hnRNP proteins, as well as the greater than 42,000 mol wt species previously identified in noncross-linked hnRNP. These proteins are shown to be cross-linked by virtue of remaining bound to the poly(A)+ hnRNA in the presence of 0.5% sodium dodecyl sulfate, 0.5 M NaCl, and 60% formamide, during subsequent oligo(dT)-cellulose chromatography, and in isopycnic banding in Cs2SO4 density gradients. These results establish that poly(A)+ hnRNA is in direct contact with a moderately complex set of nuclear proteins in vivo. This not only eliminates earlier models of hnRNP structure that were based upon the concept of a single protein component but also suggests that these proteins actively participate in modulating hnRNA structure and processing in the cell.
mesh_terms: D002500:Centrifugation, Isopycnic; D055598:Chemical Phenomena; D002621:Chemistry; D005559:Formamides; D006367:HeLa Cells; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D006801:Humans; D008970:Molecular Weight; D009698:Nucleoproteins / Q000032:analysis*; D011061:Poly A / Q000378:metabolism*; D012313:RNA / Q000378:metabolism*; D012332:RNA, Heterogeneous Nuclear / Q000032:analysis / Q000378:metabolism*; D012333:RNA, Messenger; D012261:Ribonucleoproteins / Q000032:analysis* / Q000378:metabolism; D012965:Sodium Chloride; D012967:Sodium Dodecyl Sulfate
chemical_list: D005559:Formamides; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D009698:Nucleoproteins; D012332:RNA, Heterogeneous Nuclear; D012333:RNA, Messenger; D012261:Ribonucleoproteins; D011061:Poly A; D012967:Sodium Dodecyl Sulfate; D012965:Sodium Chloride; D012313:RNA