title: A cytoplasmic ribonucleoprotein complex containing a small RNA inhibitor of protein synthesis.
abstract: Ribonucleoprotein complexes (RNP) sedimenting between 10 and 15 S were isolated from the postpolysomal cytoplasmic fraction of embryonic chicken muscle. These RNP complexes lack mRNA but contain RNA with a sedimentation coefficient of 4.4 S. The 4.4 S RNA did not arise as a product of degradation during the course of the isolation procedure nor did it contain oligo(U)- or poly(A)-rich regions. Furthermore, the 4.4 S RNA-containing RNP complex was easily separable from free mRNPs and, therefore, is not considered as part of the free mRNP complexes. Both the 4.4 S RNA and 10 to 15 S RNP were able to inhibit translation of either "capped" or "uncapped" mRNA in a heterologous cell-free system. This inhibitory effect may result from interference of 4.4 S RNA with an early event in mRNA translation. A large number of polypeptides of Mr = 14,000 to 220,000 were present in the 10 to 15 S RNP. Among these, the most prominent polypeptides were of Mr = 36,000; 48,000; 52,000; 58,000; 65,000; 78,000; 84,000; 96,000; 105,000; 165,000; and 220,000. With the exception of the Mr = 36,000 polypeptide, these major components were also found in the nonpolysomal cytoplasmic mRNA protein complexes (free mRNP).
mesh_terms: D000818:Animals; D001312:Aurintricarboxylic Acid / Q000494:pharmacology; D002642:Chick Embryo; D003600:Cytosol / Q000502:physiology; D007700:Kinetics; D008970:Molecular Weight; D009132:Muscles / Q000378:metabolism*; D009698:Nucleoproteins / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000187:drug effects; D012313:RNA / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism; D012261:Ribonucleoproteins / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D009698:Nucleoproteins; D012333:RNA, Messenger; D012261:Ribonucleoproteins; D001312:Aurintricarboxylic Acid; D012313:RNA