title: Sequence homology at the 5'-termini of insect messenger RNAs.
abstract: Treatment of insect polyribosomes with 1 M KCl released a messenger ribonucleoprotein with a pronounced 16S peak. Phenol extraction resulted in a defined peak of 10S RNA, which was judged as mRNA by the following criteria: it showed specificity for binding to ribosomes, and the formation of initiation complex was dependent on protein initiation factors, GTP, mRNA, and aminoacyl-tRNA. The complex directed protein synthesis upon the addition of elongation factors. mRNA was treated with phosphatase and phosphorylated at the 5'-end with [(32)P]cyanoethylphosphate. [(32)P]mRNA was digested by T1 ribonuclease to completion and chromatographed on DEAE-cellulose. The only fragment with (32)P was 15 nucleotides long; it was treated with pancreatic ribonuclease and fingerprinted. Fractions of AC, AAC, and AAAC were found. Initiation signal AUG or GUG in these mRNAs does not begin immediately at the 5'-end and may be at a distance greater than 15 nucleotides. Alkaline hydrolysis of mRNAs labeled in vivo with [(14)C]adenosine revealed Ap and pppAp. Alkaline hydrolysis of mRNA labeled with (32)P at the 5'-terminus resulted in pAp. Hence, these results suggest that in a heterogeneous population of mRNAs from insects, all start with A and have sequence homology at the 5'-termini. This sequence may reflect the signal for RNA polymerase on the gene or may promote the binding of mRNA to ribosomes.
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism; D000818:Animals; D001345:Autoradiography; D001483:Base Sequence; D002247:Carbon Isotopes; D002499:Centrifugation, Density Gradient; D002848:Chromatography, DEAE-Cellulose; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D010448:Peptide Initiation Factors / Q000378:metabolism; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D010759:Phosphorus Isotopes; D011132:Polyribosomes / Q000032:analysis; D011189:Potassium Chloride / Q000494:pharmacology; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000032:analysis* / Q000302:isolation & purification / Q000378:metabolism; D012260:Ribonucleases / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D013712:Tenebrio
chemical_list: D002247:Carbon Isotopes; D010448:Peptide Initiation Factors; D010759:Phosphorus Isotopes; D012333:RNA, Messenger; D011189:Potassium Chloride; D006160:Guanosine Triphosphate; D012260:Ribonucleases; D000469:Alkaline Phosphatase; D010727:Phosphoric Diester Hydrolases; D000604:Amino Acyl-tRNA Synthetases