Molecular cloning of the mouse S-adenosylmethionine decarboxylase cDNA: specific protein binding to the conserved region of the mRNA 5'-untranslated region.

The nucleotide sequence of a cDNA encoding the proenzyme of mouse S-adenosylmethionine decarboxylase (AdoMetDC) including 257 nucleotides of the 5' untranslated region has been determined. Comparison of the nucleotide sequence of the mouse 5' untranslated region with those of other mammals shows it to be highly conserved. The 52 nucleotides upstream from the translation initiation codon are identical in human, rat, bovine and mouse. The polyamines, spermidine and spermine, have been shown to inhibit AdoMetDC mRNA translation. An RNA gel retardation assay demonstrated that a cytoplasmic extract from mouse brain forms an RNA-protein complex with the completely conserved 5' untranslated sequence and that the complex formation is highly dependent on the presence of spermine. Crosslinking by UV irradiation shows that the complex contains a 39-kDa protein interacting with the 5' untranslated sequence. These data demonstrate spermine-dependent specific protein binding to a highly conserved 5' untranslated region of an mRNA translationally regulated by polyamines.     

Molecular cloning of partial cDNA copies of two distinct mouse IFN-beta mRNAs.

Two cDNA libraries were constructed, using respectively the 12S and the 16S sucrose gradient fractions of polysomal poly (A)+ RNA from mouse C243 cells induced with Newcastle disease virus. Screening of a part of both libraries by mRNA selection hybridization assays revealed the presence of two plasmids hybridizing to an mRNA, whose translation product was characterized as mouse IFN-beta. Blot analysis of RNA indicated that mRNA hybridizing to the DNA from both plasmids could be detected in induced but not in uninduced C243 cells. The two cDNA inserts did not cross hybridize and had distinct restriction maps. Sequencing revealed that both inserts represented the end of the coding region and the entire 3' non coding region of two district mRNAs. Although different, the putative 39 AA and 65 AA carboxy termini of both Mu IFN-beta s display some homology to human IFN-beta 1. Thus there are at least two different murine IFN-beta genes.