The importance of the 3'-untranslated region in the translational control of ferritin mRNA

Analysis of mRNA heterogeneity by ribonuclease H mapping: application to the insulin receptor

The major species of human insulin receptor mRNA (5.9, 7.5, 8.5 and 10.2 kb) and those in rat tissues (7.4 and 9.6 kb) are each much larger than the 4.2 kb required to encode the insulin receptor precursor. To evaluate the structural basis for this mRNA size heterogeneity, we performed a ribonuclease H mapping technique. A small insulin receptor cDNA insert was annealed to human and rat poly(A) RNA, followed by site-specific enzymatic cleavage with ribonuclease H. Subsequent Northern blot analysis with cDNA probes specific to the 5' end of the cDNA revealed a single fragment from each of the human and rat insulin receptor mRNA species. The size of this fragment indicated that each mRNA contains approximately 0.4 kb of 5' untranslated mRNA. In contrast, a 3' region probe demonstrated multiple mRNA fragments after cleavage. The sizes of these fragments indicated that the human insulin receptor mRNA species contain from 1.5 to 5.4 kb, and the rat insulin receptor mRNAs either 2.8 or 5.3 kb, of 3' untranslated RNA. Thus, the presence of varied, but extensive, 3' untranslated sequences in insulin receptor mRNA transcripts accounts for their size heterogeneity and may affect mRNA stability and/or translation efficiency.

Small cytoplasmic RNA associated with polyadenylated RNA is involved in the hormonal regulation of gene expression

The fraction of small RNA (sacc-RNA) associated with cytoplasmic rat liver poly(A)+ RNA by non-covalent, possibly complementary, interactions has been isolated and studied. Fingerprint analysis and Northern blot hybridization data reveal that the specific changes occur in the population of sacc-RNA in response to glucocorticoid treatment. The close similarity of the oligonucleotide composition of sacc-RNA and RNA-component of small nuclear RNP-acceptor of glucocorticoid hormones has been found. The hypothesis of the involvement of the small RNA in the hormonal regulation of posttranscriptional stages of gene expression in the cytoplasm has been put forward.

Differential splicing in the 3' non-coding region of rat cytochrome P-452 (P450 IVA1) mRNA

The gene coding for the clofibrate-induced cytochrome P-452 has been isolated from a cDNA library and a full-length cDNA clone sequenced. The sequence was identical with that reported by Hardwick et al. [(1987) J. Biol. Chem. 262, 801-810] apart from the presence of an additional 75 nucleotides inserted adjacent to the 3'-end of the coding region. Northern blot analysis indicates that this is probably a consequence of differential splicing, which may be relevant to the tissue-specific regulation of this gene.