title: Cross-linked proteins associated with a specific mRNA in the cytoplasm of HeLa cells.
abstract: Cytoplasmic messenger RNAs of eukaryotic cells are distributed between polysomal and post-polysomal fractions (free) as protein-bound complexes. These studies were designed to determine whether a specific mRNA isolated from different subcellular compartments is complexed with the same family of polypeptides. As a first approach we have examined the proteins associated with mRNA which codes for histone H4. To perform these experiments HeLa cells were exposed to ultraviolet light to cross-link in vivo polypeptides which are closely associated with nucleic acid. To identify the polypeptides associated with mRNA specific for histones a genomic probe for histone H4 mRNA was immobilized on epoxy-cellulose. By hybrid selection specific mRNPs containing histone mRNA were isolated. Our results reveal the existence of a number of polypeptides associated with both polysomal and post-polysomal histone mRNAs. In polysomal histone mRNA two polypeptides of Mr = 49 000 and 52 500 were the major components. In contrast polypeptides of Mr = 43 000 and 57 000 were the major polypeptide components of post-polysomal (or free) histone mRNA. Furthermore, these results also suggest that the polypeptides associated with either polysomal or free H4 histone mRNA represent a subset of proteins found in poly(A)-free fractions or poly(A)-rich mRNA fractions.
mesh_terms: D002499:Centrifugation, Density Gradient; D003593:Cytoplasm / Q000032:analysis*; D006367:HeLa Cells / Q000032:analysis*; D006657:Histones / Q000235:genetics; D006801:Humans; D046911:Macromolecular Substances; D010455:Peptides / Q000032:analysis; D011061:Poly A / Q000032:analysis; D011132:Polyribosomes / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis*; D012261:Ribonucleoproteins / Q000032:analysis* / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D006657:Histones; D046911:Macromolecular Substances; D010455:Peptides; D012333:RNA, Messenger; D012261:Ribonucleoproteins; C026452:messenger ribonucleoprotein; D011061:Poly A