title: Methylated constituents of poly(A)- and poly(A)+ polyribosomal RNA of sea urchin embryos.
abstract: We have examined the poly(A)- and poly(A)+ polyribosomal (Ps) RNAs of developing sea urchin embryos to see whether they contain the capped structures previously observed in the poly(A)+ cytoplasmic RNA (mRNA) of a variety of eucaryotic organisms. We have found that both classes of Ps RNA contain 7-methylguanosine linked to the RNA by a 5'-5' triphosphate bridge. Capped structures derived from either class of Ps RNA appear to be of the type m7G5'ppp5'NmpNp, with only a single sugar-methylated nucleoside per cap, and we have estimated that both classes of Ps RNA are capped to the same extent. The 5' terminal 2'-0-methylated nucleosides have been identified and quantitated. The relative amounts are Am = 78%, Gm = 14%, Cm = 5%, Um = 3% for poly(A)- Ps RNA, and Am = 78%, Gm = 15%, Cm = 5%, Um = 2% for poly (A)+ Ps RNA. In addition, both classes of Ps RNA contain 2-4 internal residues of N6-methyladenylic acid per molecule.
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000032:analysis; D000818:Animals; D004625:Embryo, Nonmammalian; D006151:Guanosine / Q000031:analogs & derivatives / Q000032:analysis; D008745:Methylation; D011061:Poly A / Q000032:analysis*; D011132:Polyribosomes / Q000032:analysis*; D012335:RNA, Ribosomal / Q000032:analysis*; D012617:Sea Urchins / Q000032:analysis*
chemical_list: D012335:RNA, Ribosomal; D006151:Guanosine; D011061:Poly A; D000241:Adenosine