Adenosine deaminase: characterization and expression of a gene with a remarkable promoter

The primary structure of the putative oncogene pim-1 shows extensive homology with protein kinases

We have shown previously that the putative oncogene pim-1 is frequently activated by provirus insertion in murine leukemia virus-induced T cell lymphomas. Here we describe the structure of the pim-1 gene as determined by sequencing genomic and cDNA clones. The gene has an open reading frame, encoding a protein of 313 amino acids, extending over six exons and preceded and followed by stop codons in all reading frames. Proviruses always integrate outside the protein-encoding domain, showing a high preference for a small region in the 3'-terminal exon; integration in the 3' exon results in relatively high levels of pim-1 mRNA. Computer search reveals homology between pim-1 and protein kinases: all the domains characteristic of protein kinases are conserved in the pim-1 amino acid sequence. The highest homologies were observed with the protein-serine kinases.

Complete nucleotide and encoded amino acid sequence of a mammalian myosin heavy chain gene. Evidence against intron-dependent evolution of the rod

The complete nucleotide sequence and exon/intron structure of the rat embryonic skeletal muscle myosin heavy chain (MHC) gene has been determined. This gene comprises 24 X 10(3) bases of DNA and is split into 41 exons. The exons encode a 6035 nucleotide (nt) long mRNA consisting of 90 nt of 5' untranslated, 5820 nt of protein coding and 125 nt of 3' untranslated sequence. The rat embryonic MHC polypeptide is encoded by exons 3 to 41 and contains 1939 amino acid residues with a calculated Mr of 223,900. Its amino acid sequence displays the structural features typical for all sarcomeric MHCs, i.e. an amino-terminal "globular" head region and a carboxy-terminal alpha-helical rod portion that shows the characteristics of a coiled coil with a superimposed 28-residue repeat pattern interrupted at only four positions by "skip" residues. The complex structure of the rat embryonic MHC gene and the conservation of intron locations in this and other MHC genes are indicative of a highly split ancestral sarcomeric MHC gene. Introns in the rat embryonic gene interrupt the coding sequence at the boundaries separating the proteolytic subfragments of the head, but not at the head/rod junction or between the 28-residue repeats present within the rod. Therefore, there is little evidence for exon shuffling and intron-dependent evolution by gene duplication as a mechanism for the generation of the ancestral MHC gene. Rather, intron insertion into a previously non-split ancestral MHC rod gene consisting of multiple tandemly arranged 28-residue-encoding repeats, or convergent evolution of an originally non-repetitive ancestral MHC rod gene must account for the observed structure of the rod-encoding portion of present-day MHC genes.

Scrapie and cellular PrP isoforms are encoded by the same chromosomal gene

PrP 27-30 is the major protein in purified preparations of scrapie agent. An almost complete PrP cDNA was used to select PrP-related genomic clones from normal hamster DNA. The gene contains a noncoding exon of 56 to 82 bp and a 2 kb coding exon, separated by a 10 kb intron. Transcription initiates at the same multiple sites in vivo and in vitro. The promoter lacks a TATA box and contains three repeats of the sequence GCCCCGCCC, which resembles the Sp1 binding site found in "housekeeping" genes. The PrP coding sequence encodes a presumptive amino-terminal signal peptide. The primary structure of PrP encoded by the gene of a healthy animal does not differ from that encoded by a cDNA from a scrapie-infected animal, suggesting that the different properties of PrP from normal and scrapie-infected brains are due to post-translational events.

CpG-rich islands and the function of DNA methylation

It is likely that most vertebrate genes are associated with 'HTF islands'--DNA sequences in which CpG is abundant and non-methylated. Highly tissue-specific genes, though, usually lack islands. The contrast between islands and the remainder of the genome may identify sequences that are to be constantly available in the nucleus. DNA methylation appears to be involved in this function, rather than with activation of tissue specific genes.

Expression of the mouse HPRT gene: deletional analysis of the promoter region of an X-chromosome linked housekeeping gene

The mouse hypoxanthine phosphoribosyltransferase gene, like several other housekeeping genes, lacks many of the features associated with promoters of RNA polymerase II-transcribed genes. HPRT transcripts have multiple initiation sites and an HPRT minigene was used to show that only 49 bases of 5' flanking sequence was necessary for normal expression in cultured cells. The essential region, which occurs within a complex series of direct repeats, is homologous to sequences upstream of other housekeeping genes. When this sequence was deleted, cryptic upstream initiation sites were revealed. Similar aberrant patterns of initiation were seen with all minigenes assayed in Xenopus oocytes. We speculate that this region of the HPRT promoter is involved in a different interaction with the transcriptional machinery to that occurring at more conventional promoters.

Transcription factor Sp1 recognizes a DNA sequence in the mouse dihydrofolate reductase promoter

Human (HeLa) cells contain a host-cell-encoded transcription factor, Sp1, which is required for transcription of simian virus 40 (SV40) promoters. Since the discovery of Sp1 we have been interested in learning what role this factor plays in uninfected cells. A monkey cellular gene promoter interacts with Sp1, but no gene products linked to this promoter have yet been identified. The finding that the sequence of the 5'-flanking DNA of the mouse dihydrofolate reductase (DHFR) gene contains several regions showing strong homology to the Sp1 binding region of simian virus 40 (SV40) prompted us to undertake experiments with dhfr. We report here that Sp1 binds to these regions in the dhfr promoter, and that Sp1-containing preparations stimulate transcription from the dhfr promoter in an in vitro reaction. Our results suggest that in addition to its interactions with the SV40 viral promoter, one function of Sp1 is to direct the expression of the cellular DHFR gene.

Promoter region of the human Harvey ras proto-oncogene: similarity to the EGF receptor proto-oncogene promoter

Regulation of transcription of members of the ras gene family undoubtably plays an important role in controlling cellular growth. Examination of this level of regulation requires identification of the promoter regions of the ras proto-oncogenes. Four major transcriptional start sites were detected in the human Harvey ras 1 proto-oncogene. The promoter region contains neither a TATA box nor a CAAT box in their characteristic upstream positions, has an extremely high G+C content (80 percent), and contains multiple GC boxes including seven CCGCCC repeats and three repeats of the inverted complement, GGGCGG. This region has strong promoter activity when placed upstream from the chloramphenicol acetyl transferase gene and transfected into monkey CV1 cells. In these ways the Harvey ras 1 proto-oncogene promoter resembles the promoter of the gene encoding the epidermal growth factor (EGF) receptor. The similarity between the two proto-oncogene promoters may be relevant to the mechanism by which the expression of such "growth control" genes is regulated.

Control of eukaryotic messenger RNA synthesis by sequence-specific DNA-binding proteins

The enzymatic machinery that carries out RNA synthesis provides the cell with the means to adjust the patterns of transcription in response to environmental and developmental signals. In eukaryotes, this regulation is mediated in part by promoter-specific transcription factors, which are DNA-binding proteins with the ability to discriminate between distinctive DNA sequence elements found in the promoter regions of different genes. The presence of these factors bound to DNA enables other components of the transcriptional machinery, including the RNA polymerase, to initiate transcription with selectivity and accuracy.

Human transforming growth factor-beta complementary DNA sequence and expression in normal and transformed cells

The partial amino-acid sequence of purified human transforming growth factor-beta (TGF-beta) was used to identify a series of cDNA clones encoding the protein. The cDNA sequence indicates that the 112-amino acid monomeric form of the natural TGF-beta homodimer is derived proteolytically from a much longer precursor polypeptide which may be secreted. TGF-beta messenger RNA is synthesized in various normal and transformed cells.

Structure of the murine Thy-1 gene

We have cloned the murine Thy-1.1 (AKR) and Thy-1.2 (Balb/c) genes. The complete exon/intron structure and the nucleotide sequence of the Thy-1.2 gene was determined. The gene contains four exons and three intervening sequences. The complete transcriptional unit gives rise to a tissue and developmental stage-specific mRNA of 1850 bp. The 5' end of the gene has multiple initiation sites and a non-TATA box promoter. The 3' end shows a single polyadenylation site after a very long untranslated region.

Introduction of sequences encoding functional human adenosine deaminase into mouse cells using a retroviral shuttle system

A retroviral packaging system was used to generate a murine virus carrying sequences encoding human adenosine deaminase (ADA). To this end, human ADA cDNA was inserted into the retroviral shuttle vector pZIP-NeoSV(X)1. This vector provides all of the cis-acting sequences necessary for the efficient packaging and transmission of the viral genome as well as a selectable gene for G418 resistance. Transfection of this recombinant plasmid into cells that provide essential virus products (psi-2 cells) yielded cell lines that stably produced virions carrying the coding sequence of human ADA. We have used these virions to infect NIH3T3 cells, which after 48 h synthesized catalytically active human ADA. Furthermore, G418-resistant cell lines were obtained from the virus-infected NIH3T3 cells that stably produced the human ADA enzyme.