title: Methylated blocked 5' terminal sequences of sea urchin embryo messenger RNA classes containing and lacking poly(A).
abstract: Sea urchin embryo mRNAs of three distinct classes--histone mRNA, nonhistone mRNA containing poly(A), "[+A] mRNA," and nonhistone mRNA lacking poly(A), "[-A]mRNA"--all contain blocked 5' terminal sequences in which 7-methylguanosine is linked 5'-5' via a triphosphate bridge to a 2'-0-methylated nucleotide. Only one general type of 5' terminal structure, 7mGpppXmpYp, is present. Additional 2'-0-methylation in the Y residue has not been found either in early or late stage embryos. A substantial proportion of the polyribosomal mRNAs in all three classes contain this blocked structure. Whereas both classes of nonhistone mRNAs have internal base methylations, histone mRNAs lack such modifications.
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000032:analysis; D000818:Animals; D001483:Base Sequence; D003562:Cytidine / Q000031:analogs & derivatives / Q000032:analysis; D004625:Embryo, Nonmammalian; D006151:Guanosine / Q000031:analogs & derivatives / Q000032:analysis; D006657:Histones / Q000096:biosynthesis*; D008745:Methylation; D011061:Poly A / Q000032:analysis*; D012333:RNA, Messenger / Q000032:analysis* / Q000378:metabolism; D012617:Sea Urchins / Q000032:analysis*; D014529:Uridine / Q000031:analogs & derivatives / Q000032:analysis
chemical_list: D006657:Histones; D012333:RNA, Messenger; D006151:Guanosine; D011061:Poly A; D003562:Cytidine; D000241:Adenosine; D014529:Uridine