Construction of a new plasmid vector that can express cloned cDNA in all translational reading frames

A novel genetic system to isolate a dominant negative effector on DNA-binding activity of Oct-2

Recent studies have revealed that interactions between transcription factors play an important role in regulation of gene expression in eukaryotic cells. To isolate cDNA clones that dominantly inhibit the DNA-binding activity of Oct-2, chosen as a representative factor, we have developed a novel screening system. This employs an Escherichia coli tester strain carrying a modified lac operon as a reporter gene, with the lac operator sequence replaced by an octamer sequence. Oct-2 expressed in this tester strain represses the expression of the reporter gene and changes the phenotype of the cell from Lac+to Lac-. Introduction of a cDNA expression library prepared from a human T-cell line into the Oct-2-harboring tester strain allowed selection of three Lac+clones out of 1 x 10(5) transformants. One of them, hT86, encoding a putative zinc finger protein was found to derepress beta-galactosidase activity in the Oct-2-harboring tester strain at the transcriptional level. In gel mobility shift assays, hT86 attenuated the intensity of the retarded band composed of the octamer probe and Oct-2, suggesting a dominant negative effect on the DNA-binding activity of Oct-2. The strategy described here provides a new approach for studying protein-protein interactions that govern the complex regulation of gene expression.

Site-directed mutagenesis of Lys600 in phosphoenolpyruvate carboxylase of Flaveria trinervia: its roles in catalytic and regulatory functions

Phosphoenolpyruvate carboxylases from various organisms contain two conserved lysine residues. In the C4 dicot Flaveria trinervia, one of these residues is Lys600. Converting this Lys600 to Arg600 or Thr600 mainly increased the Km values and but had minimal effect on the Vmax. The Km for PEP, Mg2+ increased by up to 3-fold in Arg600 and Thr600 but the Km (HCO3-) increased 9-fold in Thr600, suggesting that Lys600 might be associated with bicarbonate-binding. This lysine was not obligatory for enzyme activity although the wild-type protein showed higher activity at physiological pH and was less inhibited by malate than the two mutants.

Human cytoplasmic isoleucyl-tRNA synthetase: selective divergence of the anticodon-binding domain and acquisition of a new structural unit

We show here that the class I human cytoplasmic isoleucyl-tRNA synthetase is an exceptionally large polypeptide (1266 aa) which, unlike its homologues in lower eukaryotes and prokaryotes, has a third domain of two repeats of an approximately 90-aa sequence appended to its C-terminal end. While extracts of Escherichia coli do not aminoacrylate mammalian tRNA with isoleucine, expression of the cloned human gene in E. coli results in charging of the mammalian tRNA substrate. The appended third domain is dispensable for detection of this aminoacylation activity and may be needed for assembly of a multisynthetase complex in mammalian cells. Alignment of the sequences of the remaining two domains shared by isoleucyl-tRNA synthetases from E. coli to human reveals a much greater selective pressure on the domain needed for tRNA acceptor helix interactions and catalysis than on the domain needed for interactions with the anticodon. This result may have implications for the historical development of an operational RNA code for amino acids.

Structure of the chicken growth hormone-encoding gene and its promoter region

We have cloned the chicken (c) growth hormone (GH)-encoding gene cGH and analyzed its nucleotide sequence including 500 bp of the 5'-flanking region. The cGH gene consists of five exons and four introns as has been observed in the mammalian GH genes. However, the size of the cGH gene is significantly larger than that of analogous mammalian genes, because of its intron size which expands it to 3.5 kb. The transcription start point was determined to be 56 bp upstream from the start codon by the primer-extension analysis. The promoter region of the cGH gene has no overall homology with the corresponding regions of mammalian genes, but contains a short (24 bp) sequence which is highly homologous to the antisense strand sequence of the proximal binding site for a pituitary-specific transcription factor, GHF-1/Pit-1, in the promoter region of the rat GH gene.

Nucleotide sequence of cDNA and primary structure for hard tail growth hormone

Full-length cDNA for hard tail growth hormone (htGH) has been cloned, and the nucleotide and deduced amino acid sequences have been analyzed. htGH is composed of 188 amino acid residues, and it shows 79, 74, 72, 59, 56, 37, 33 and 30% identity of amino acid with yellow tail, tuna, sea bream, flounder, salmon, blue shark, bullfrog and human GHs, respectively.

65-kilodalton protein phosphorylated by interleukin 2 stimulation bears two putative actin-binding sites and two calcium-binding sites

We have previously characterized a 65-kilodalton protein (p65) as an interleukin 2 stimulated phosphoprotein in human T cells and showed that three endopeptide sequences of p65 are present in the sequence of l-plastin [Zu et al. (1990) Biochemistry 29, 1055-1062]. In this paper, we present the complete primary structure of p65 based on the cDNA isolated from a human T lymphocyte (KUT-2) cDNA library. Analysis of p65 sequences and the amino acid composition of cleaved p65 N-terminal peptide indicated that the deduced p65 amino acid sequence exactly coincides with that of l-plastin over the C-terminal 580 residues [Lin et al. (1988) Mol. Cell. Biol. 8, 4659-4668] and has a 57-residue extension at the N-terminus to l-plastin. Computer-assisted structural analysis revealed that p65 is a multidomain molecule involving at least three intriguing functional domains: two putative calcium-binding sites along the N-terminal 80 amino acid residues; a putative calmodulin-binding site following the calcium-binding region; and two tandem repeats of putative actin-binding domains in its middle and C-terminal parts, each containing approximately 240 amino acid residues. These results suggest that p65 belongs to actin-binding proteins.

Sequence requirements for nucleolar localization of human T cell leukemia virus type I pX protein, which regulates viral RNA processing

The posttranscriptional regulator (p27x-III) of human T cell leukemia virus type I (HTLV-I) is located predominantly in the cell nucleolus. A highly basic amino-terminal sequence (NH2-Met-Pro-Lys-Thr-Arg-Arg-Arg-Pro-Arg-Arg-Ser-Gln-Arg-Lys-Arg-Pro-Pro -Thr- Pro) in this protein, when fused to the amino termini of beta-galactosidase and p40x of HTLV-I, acts as an autonomous signal capable of directing the hybrid proteins to the cell nucleolus.

Expression of recombinant growth hormone in Escherichia coli: effect of the region between the Shine-Dalgarno sequence and the ATG initiation codon

We constructed a synthetic Escherichia coli expression system in which various promoter elements can be changed easily. In this study we investigated the effect of a number of portable Shine-Dalgarno regions (SD regions) on the synthesis of two modified recombinant human growth hormones (hGH). The production of these modified hGH was measured during exponential growth and after the bacteria had reached stationary phase. The results show that the optimal distance between the SD region (AGGAGG) and the ATG start codon is approximately 11 nucleotides. However, the nucleotide sequence in this region also influences expression: 6-10 adenines result in comparable expression levels despite the varying lengths. Two overlapping SD regions reduce expression of the growth hormones considerably, whereas two potential ATG start codons do not affect expression. Having a SD-ATG region partly or totally complementary to the 5' end of the 16S ribosomal RNA does not alter translation efficiency. Estimation of the delta G values for the association between the 16S rRNA and the ribosome-binding region suggests that these are not indicators of expression efficiency.

cDNA cloning and primary structure of yellow tail (Seriola quinqueradiata) pregrowth hormone

Full-length cDNA of yellow tail (Seriola quinqueradiata) growth hormone (GH) was cloned from the pituitary gland and nucleotide sequence was analyzed. The cDNA clone contained one open reading frame to encode a preprotein consisting of 204 amino acids. The deduced amino acid sequence shows two possible sites for signal peptide cleavage, suggesting that the mature forms of yellow tail growth hormone consist of 185 or 187 amino acids. Yellow tail growth hormone exhibits a typical structural feature as growth hormone, including four cysteine residues to form two disulfide bonds and other identical amino acids with other vertebrate GHs. Amino acid sequence of yellow tail growth hormone shows homology of approximately 66, 42, 37, and 34% with those of salmon, eel, bovine, and human GHs, respectively. Nucleotide sequence of the coding region of yellow tail growth hormone cDNA shows approximately 58 and 40% homology with those of salmon and human growth hormone cDNAs, respectively.

Further analysis of cDNA clones for maize phosphoenolpyruvate carboxylase involved in C4 photosynthesis. Nucleotide sequence of entire open reading frame and evidence for polyadenylation of mRNA at multiple sites in vivo

Four clones of cDNA for phosphoenolpyruvate carboxylase [EC 4.1.1.31] were obtained from a maize green leaf cDNA library by colony hybridization. The largest cDNA was of full-length (3335 nucleotides), being 243 nucleotides longer than the cDNA cloned previously [(1986) Nucleic Acids Res. 14, 1615-1628]. Alignment of the sequence for the N-terminal coding region found in two of the four clones with the sequence reported previously, established the sequence of the entire coding region for the enzyme. The sequencing of 3'-untranslated region of the clones revealed that the poly(A) tract is attached at multiple sites in vivo.