Posttranscriptional gene regulation and specific binding of the nonhistone protein HMG-I by the 3' untranslated region of bovine interleukin 2 cDNA.

Abstract

The 3' untranslated tail region (3'-UTR) of the cDNA of bovine interleukin 2 (bIL-2) acts as a lymphoid cell-specific gene regulatory element in vivo when ligated to the 3' end of the "marker" bacterial gene coding for chloramphenicol acetyltransferase (CAT) and the hybrid fusion gene is introduced into bovine lymphoid cells by transfection. Evidence is also presented that the 3'-UTR with its conserved (TATT). motif probably has multiple functions in lymphoid cells operating both at the chromosomal level, where the sequence may be involved in the specific binding of the nonhistone chromatin high mobility group protein HMG-I, and at the RNA level, where the conserved sequence is involved in selective posttranscriptional mRNA degradation by a lymphocyte-specific nuclease(s). These results suggest a complex in vivo role for the 3'-UTR of bIL-2 cDNA and the conserved (TATT)n sequences found within it. They also offer a plausible explanation for the high degree of conservation of similar A+T-rich sequences in the 3'-UTRs of many of the other immuneresponse and growth-regulatory genes of mammals.A common control feature shared by many lymphokine, cytokine, growth-factor, and immune-response genes of mammals is the dual operation of both transcriptional and posttranscriptional mechanisms to regulate their expression in vivo (1)(2)(3)(4)(5)(6)(7)(8). From detailed analyses of the cDNAs and genomic molecular clones coding for some of these genes, certain of the DNA sequences involved in the cell-specific inducible promotion (9-11) and enhancement (12) of transcription, as well as sequences involved in posttranscriptional processes (2,5,(13)(14)(15), have been identified. In this regard we (13), and others (14, 15), have recently identified long stretches (>20 nucleotides) of a highly conserved A+U-rich sequence commonly found in the 3' untranslated tail region (3'-UTR), between the termination codon and the polyadenylylation signal, of the mRNAs of many of the known lymphokine, cytokine, and protoonco-genes. At the DNA level this conserved sequence appears to be composed of tandem repeats of an ancestral tetranucleotide (TATT) unit that has undergone limited divergence during the evolution of these genes (13). Significantly, not all of the genes known to be induced during the immune activation of lymphocytes [e.g., the interleukin-2 (IL-2) receptor (16), the transferrin receptor (17), and certain proteases (18)] have such canonical sequence motifs in their 3'-UTRs, suggesting that these highly conserved (TATT)n sequences may serve specific regulatory or other roles in those genes that do possess them. Here we report on multiple functions found to be associated with the 3'-UTR ofthe cDNA of bovine interleukin-2 (bIL-2). MATERIALS AND METHODSCell Culture and DNA Transfections. Adherent strains of IL-2-dependent bovine lymphoid cells (e.g., E3 and 27X) were derived and maintained as previously described (13) 6531The publication costs of this article were defrayed in part by page charge payment. This article must t...

Architecture of High Mobility Group Protein I-C·DNA Complex and Its Perturbation upon Phosphorylation by Cdc2 Kinase

“…Binding to the Long AT Stretches of DNA Involves Three AT-hooks-Synthetic poly(dA-dT)⅐poly(dA-dT) is often used as a model of a binding site of HMGI(Y) proteins (12, 13, 16) since it resembles long AT stretches, which play a role in regulatory elements of some genes, where these proteins bind (43). There- fore, a protein footprint with HMGI-C was carried out in the absence or presence of poly(dA-dT)⅐poly(dA-dT) (32 bp/molecule HMGI-C) (Fig.…”

An intronic 10-base-pair deletion in a class II A beta gene affects RNA processing.

“…However, an AT-rich sequence has recently been identified that causes selective mRNA degradation when introduced into the 3' untranslated region of the ,B-globin gene, which normally produces a stable mRNA (32). This AT-rich sequence has been found in the 3' untranslated region of a number of posttranscriptionally regulated genes, including the human beta and gamma interferons as well as the bovine interleukin-2 gene (2,25,32 this 3' AU-rich sequence may be involved in these events (24).…”

“…However, an AT-rich sequence has recently been identified that causes selective mRNA degradation when introduced into the 3' untranslated region of the ,B-globin gene, which normally produces a stable mRNA (32). This AT-rich sequence has been found in the 3' untranslated region of a number of posttranscriptionally regulated genes, including the human beta and gamma interferons as well as the bovine interleukin-2 gene (2,25,32 this 3' AU-rich sequence may be involved in these events (24).The sequence requirements, if any, for intranuclear stability or transport of heterogeneous nuclear RNA (hnRNA) to the splicing machinery are unknown, although consensus splice site sequences have been identified. Recently, an intronic point mutation within the c-Ha-ras oncogene has been shown to cause a 10-fold increase in expression that may be mediated by increased hnRNA stability (7).…”

“…Recently, it has become apparent that many genes are regulated at the posttranscriptional level (8,24,36). One notable instance involves the immunoglobulin heavy-chain gene.…”

“…This AT-rich sequence has been found in the 3' untranslated region of a number of posttranscriptionally regulated genes, including the human beta and gamma interferons as well as the bovine interleukin-2 gene (2,25,32). A labile nuclease in bovine lymphoid and CV-1 fibroblast cells that selectively destroys interleukin-2 mRNA and other mRNAs containing this 3' AU-rich sequence may be involved in these events (24).…”