Isolation and mapping of a gene for protein synthesis initiation factor 4A and its expression during differentiation of murine erythroleukemia cells.
Eukaryotic protein synthesis initiation factor 4A (eIF-4A), a 46-kDa polypeptide, is involved both in mRNA cap recognition and in the binding of mRNA to 40S ribosomal subunits. A 41-mer oligodeoxynucleotide probe was synthesized complementary to a portion of the published coding sequence of eIF-4A mRNA [Nielsen et al., Nucleic Acids Res. 13 (1985) 6867-6870] and used to screen a mouse genomic library. We have isolated and characterized a full-length clone from that library. The eIF-4A sequence is contained in eleven exons. The eleventh exon also has the 3'-nontranslated sequence and two separate polyadenylation sites. Northern-blot analysis of mouse poly(A)+RNA indicates that there are several distinct mRNA species coding for eIF-4A. Two of these contain the same coding sequence and differ only in the length of the 3'-nontranslated region. Two of the eIF-4A mRNAs are therefore likely to be the result of differential processing at the 3'-end. We have used a fragment of the genomic clone to measure the steady-state levels of eIF-4A mRNA during the induced differentiation of murine erythroleukemia cells. S1 nuclease protection experiments demonstrated that by the fourth day after induction eIF-4A mRNA declined to 25% of its steady-state level in uninduced cells. In contrast, the steady-state level of beta-globin mRNA increased dramatically during differentiation. In vitro transcription assays using nuclei isolated from uninduced and induced cells show that the rate of transcription of eIF-4A mRNA was 40% greater in differentiated cells, indicating a posttranscriptional component is involved in the regulation of the steady-state mRNA level.
Reddy
N S
NS
Department of Biochemistry, University of Mississipi Medical Center, Jackson 39216-4505.
Roth
W W
WW
Bragg
P W
PW
Wahba
A J
AJ
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000502:physiology; D003001:Cloning, Molecular; D004912:Erythrocytes / Q000166:cytology*; D039601:Eukaryotic Initiation Factor-4A; D005091:Exons; D005786:Gene Expression Regulation; D005796:Genes; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes / Q000138:chemical synthesis; D010448:Peptide Initiation Factors / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis; D015183:Restriction Mapping; D014407:Tumor Cells, Cultured
D015345:Oligonucleotide Probes; D010448:Peptide Initiation Factors; D012333:RNA, Messenger; D039601:Eukaryotic Initiation Factor-4A