Rat prostatic steroid binding protein: characterisation of the Alu element upstream of the C3 genes

Complete nucleotide sequence, origin of isoform and functional characterization of the mouse hepsin gene

Hepsin, a type-II membrane-associated serine protease, has been implicated in cell growth and development as well as possible initiation of blood coagulation. Here, we report on the complete nucleotide sequence, functional characterization of key structural features and the promoter of the mouse hepsin gene. The gene has a size of approximately 17 kb, and is composed of 12, 13, or 14 exons depending on alternative intron splicings - one in the 5'-UTR and the other two in the second intron. The latter two, which occur in approximately half of the hepsin transcripts, generate a hepsin mRNA species with an extra exon, which is responsible for producing a hepsin isoform with a unique 20-residue sequence inserted in the cytoplasmic portion of hepsin. Most hepsin transcripts have the 5'-UTR intron spliced, and its splicing can occur independently of the other alternative splicings. The transcriptional initiation site was determined to be 636 bp upstream of the first ATG site in a cytidine-rich region. The 5'-flanking region of hepsin up to nucleotide 274 showed a substantial promoter activity in HepG2 cells, with its expression activity sevenfold higher in the presence of the 5'-UTR intron sequence in comparison to that without the intron sequence. The basal promoter region contains potential binding sites for several transcription factors including SP1, AP2, C/EBP, LF-A1, and E box, which may be responsible for ubiquitous, but liver- and kidney-preferred tissue expression of the hepsin gene.

Hepadna virus integration generates virus-cell cotranscripts carrying 3' truncated X genes in human and woodchuck liver tumors

Integration of the human and woodchuck hepatitis B viruses (HBV and WHV) in host chromosomes has been implicated in the development of hepatocellular carcinoma by different cis- and trans-acting mechanisms. The structure and coding capacity of abundant HBV and WHV transcripts of abnormal sizes produced from integrated viral sequences in one human and two woodchuck liver tumors were examined. Analysis of cDNA clones revealed in all cases hybrid virus-cell transcripts containing sequences of the viral surface gene, the viral enhancer, and different truncated versions of the viral X transactivator. Cotranscribed cellular sequences showing no significant coding function provided the signals for transcription termination. In two transcripts, the HBX and WHX genes truncated at carboxy terminal positions conserved transcriptional trans-acting capacity in transient transfection assays. These results lend support to the hypothesis that the integrated hepadnavirus X transactivator might participate in the development of woodchuck as well as human liver tumors by a common trans-acting mechanism.

Isolation, structure and expression of cDNA and genomic clones for murine eosinophil differentiation factor. Comparison with other eosinophilopoietic lymphokines and identity with interleukin-5

Eosinophil differentiation factor (EDF) is a recently described regulator affecting eosinophil growth and activation. cDNA clones for murine EDF were isolated by direct expression from libraries prepared from the T cell hybrid NIMP-TH1. The longest cDNA clone obtained was 1534 bp in length encoding a polypeptide of 133 amino acids. Two variant cDNAs suggesting alternative RNA processing events were detected. The EDF gene was cloned from a genomic lambda library and a region of 6727 bp encompassing the gene was sequenced. The gene contains three introns 829, 1875 and 79 bases in length and has numerous repetitive sequences. A common, possible regulatory element, including a conserved decamer, lies adjacent to the TATA boxes of the EDF and granulocyte-macrophage colony-stimulating factor (GM-CSF) genes and similar sequences are present in some other lymphokine genes. Recombinant EDF produced in monkey COS cells strongly stimulated the eosinophil lineage and also showed B-cell-growth factor II (BCGFII) activity whereas recombinant murine interleukin-3 and GM-CSF showed much broader activity towards the different myeloid lineages, were less active on eosinophils and had no BCGFII activity. The BCGFII activity of recombinant EDF together with a comparison of the BCGFII (interleukin-5) cDNA sequence with that of the EDF cDNA establishes that these two activities are the properties of a single polypeptide.

A role for ID repetitive sequences in growth- and transformation-dependent regulation of gene expression in rat fibroblasts

A set of mRNAs tagged by repetitive sequences of the ID family were found to accumulate following growth-factor-induced transition of normal (FR3T3) rat fibroblasts from a quiescent to a proliferative state. The levels of the same transcripts were also increased following transformation by polyoma virus and by ras and myc oncogenes. The presence of the ID element appeared to be determinant, since a similar pattern of expression was observed for a construct where one element had been inserted in the 3' noncoding region of a rabbit beta-globin gene expressed under control of an SV40 promoter.

Stable accumulation of a rat truncated repeat transcript in Xenopus oocytes

To define potential mechanisms of expression of middle-repetitive DNA, Xenopus oocytes were employed to examine the rat type 2 and truncated repeat (TR) elements contained in an intron and in the 3'-flanking region of the rat growth hormone gene. These repeats contain significant sequence and structural homology to tRNA genes and, thus, may represent tRNA pseudogenes. Transcripts from the type 2 elements do not accumulate in the cytosol and are found predominantly in the nucleus, whereas those from TR DNA are expressed in the cytosol of neural and pituitary tissues. In HeLa cell extracts, the rat growth hormone type 2 sequences initiate RNA polymerase III transcription resulting in multiple transcripts of 175-970 nucleotides; some of these also contain TR sequences that are present only as downstream structures since the rat growth hormone-TR DNA lacks promoter activity. In Xenopus oocytes the same template also results in multiple transcripts, but with time a single, homogeneous 73-base RNA preferentially accumulates. This RNA probably arises from larger repetitive DNA transcripts as assessed by the kinetics of its formation, its 5' terminus, and the injection of transcripts generated in HeLa cell-free extracts into the oocytes. Sequence analysis of the 73-base RNA suggests that it is a TR transcripts derived from the TR region with tRNA homology. Stable type 2 transcripts were not detected. Thus, type 2 elements are transcribed in the oocytes, but RNAs from them are degraded whereas discrete TR DNA transcripts can be derived from larger RNA molecules and can accumulate in the cytosol due to their preferential stability. These findings indicate that posttranscriptional control mechanisms can operate to direct differential expression of closely related repetitive DNAs and suggest that structures similar to tRNA contained within the TR sequences may allow them to accumulate preferentially in the cytoplasm.