Human beta-globin mRNAs that harbor a nonsense codon are degraded in murine erythroid tissues to intermediates lacking regions of exon I or exons I and II that have a cap-like structure at the 5' termini

EMBO J. 1992 Sep;11(9):3271-8.

Abstract

Previous studies have demonstrated that nonsense codons within beta zero-thalassemic or in vitro-mutagenized human beta-globin transgenes result in the production of mRNAs that are degraded abnormally rapidly in the cytoplasm of murine erythroid cells. As a consequence, three RNA degradative intermediates are formed that lack sequences from either exon I or exons I and II. We show here that the intermediates, like the full-length mRNA from which they derive and the endogenous murine beta maj-globin mRNA, bind to the anticap monoclonal antibody H-20 in a way that is competed by the cap analogue m7G and eliminated by prior exposure to tobacco acid pyrophosphatase. Furthermore, the intermediates, like the two full-length mRNAs, are resistant to a 5'----3' exonuclease activity isolated from HeLa cell nuclei that degrades uncapped but not capped ribopolymers. Based on these observations, the intermediates appear to possess a structure that is indistinguishable from the cap at the 5' end of mRNA, i.e. a methylated nucleoside that is linked to the RNA by a 5'-5' phosphodiester bond. Detection of the intermediates during murine development was concomitant with detection of full-length thalassemic mRNA. Intermediate production appears to be influenced by RNA structure as indicated by the products that derive from a beta zero-thalassemic beta-globin transgene harboring a structural alteration (a 4 bp deletion) that was larger than any of those previously studied.

MeSH terms

  • Animals
  • Antibodies, Monoclonal
  • Base Sequence
  • Codon*
  • Erythroid Precursor Cells / metabolism
  • Exons
  • Exonucleases / pharmacology
  • Globins / genetics*
  • Humans
  • Methylation
  • Methyltransferases
  • Mice
  • Molecular Sequence Data
  • Pyrophosphatases / pharmacology
  • RNA Caps / isolation & purification
  • RNA Caps / metabolism*
  • RNA Processing, Post-Transcriptional*
  • RNA, Messenger / drug effects
  • RNA, Messenger / genetics
  • RNA, Messenger / immunology
  • RNA, Messenger / metabolism*
  • Spleen / metabolism
  • Thalassemia / genetics*

Substances

  • Antibodies, Monoclonal
  • Codon
  • RNA Caps
  • RNA, Messenger
  • Globins
  • Methyltransferases
  • Exonucleases
  • Pyrophosphatases