Inhibition of CCAAT/enhancer-binding protein alpha and beta translation by upstream open reading frames

J Biol Chem. 1998 Apr 17;273(16):9552-60. doi: 10.1074/jbc.273.16.9552.

Abstract

CCAAT/enhancer-binding protein (C/EBP) alpha is a bZIP transcription factor whose expression is restricted to specific cell types. Analysis of C/EBPalpha mRNA and protein levels in various mammalian cells indicates that expression of this gene is controlled both transcriptionally and post-transcriptionally. We report here that C/EBPalpha translation is repressed in several cell lines by an evolutionarily conserved upstream open reading frame (uORF), which acts in cis to inhibit C/EBPalpha translation. Mutations that disrupt the uORF completely abolished translational repression of C/EBPalpha. The related c/ebpbeta gene also contains an uORF that suppresses translation. The length of the spacer sequence between the uORF terminator and the ORF initiator codon (7 bases in all c/ebpalpha genes and 4 bases in c/ebpbeta homologs) is precisely conserved. The effects of insertions, deletions, and base substitutions in the C/EBPalpha spacer showed that both the length and nucleotide sequence of the spacer are important for efficient translational repression. Our data indicate that the uORFs regulate translation of full-length C/EBPalpha and C/EBPbeta and do not play a role in generating truncated forms of these proteins, as has been suggested by start site multiplicity models.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3T3 Cells
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • CCAAT-Enhancer-Binding Proteins
  • Cattle
  • Cell Line
  • Chickens
  • DNA, Ribosomal / metabolism
  • DNA-Binding Proteins / biosynthesis*
  • DNA-Binding Proteins / genetics
  • Gene Expression Regulation*
  • HeLa Cells
  • Humans
  • Male
  • Mice
  • Molecular Sequence Data
  • Nuclear Proteins / biosynthesis*
  • Nuclear Proteins / genetics
  • Open Reading Frames*
  • Protein Biosynthesis*
  • Rats
  • Regulatory Sequences, Nucleic Acid
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Transcription Factors / biosynthesis
  • Transfection
  • Xenopus laevis

Substances

  • CCAAT-Enhancer-Binding Proteins
  • DNA, Ribosomal
  • DNA-Binding Proteins
  • Nuclear Proteins
  • Transcription Factors