摘要:

Mts1is a metastasis-associated gene of the S-100 gene family and codes for a Ca2+-binding protein. It is highly expressed in murine and human cancers of high invasive and metastatic potential. Recent work has shown that the mts1 protein might be involved in cell cycle regulation. An upregulation of its expression drives cells into the S phase, together with an enhanced expression of p53 phosphoprotein, which has led to the suggestion that mts1 protein might be sequestering p53 thereby abrogating the G1-S checkpoint control normally exerted by p53. Preliminary studies showed that expression ofmts1is downregulated by hyperthermia. We present evidence that in murine BL6 melanoma cells and human HUT cells that hyperthermia downregulates themts1gene. It is also downregulated in heat-resistant variants of the B16 melanoma and HUT cells. In parallel, there is a decrease in the size of the S phase fraction and an increase in the doubling time of cells. Cell subjected to hyperthermia show an 2- to 3.5-fold increase in the expression of HSP28 which has been shown to possess a proliferation inhibitory action. It is postulated that a complete regulatory loop involving mts1, p53, and HSP28 might be involved in cell proliferation.

ISSN:1044-5498    

DOI:10.1089/dna.1998.17.1

年代:1998

数据来源: MAL

摘要:

P21 is a regulatory protein that can contribute to cell cycle arrest by inhibiting the [unk]yclin-[unk]ependent-[unk]inases (cdks). However, the mechanism that links the inhibition of the cdk activities and the cell cycle arrest is not well established. To investigate this, we studied a purified endogenous cellular complex which contained E2F (in the form of E2F-4), p 130, cyclin, and cdk2. This complex of E2F-pl30-cyclin-cdk2 is found mainly in cycling cells and is postulated to be an intermediate that leads to the activation of E2F. We previously showed that p21 could disrupt this complex leading to the accumulation of an E2F-pl30 complex and the inhibition of E2F-regulated transcription. We analyzed a group of p21 mutants including those that harbored changes in cyclin- and cdk2-binding motifs. We show that both the cyclin and cdk2 binding motifs of p21 are crucial for the disruption of this endogenous complex of E2F-pl30-cyclin-cdk2. This suggests a model where the ability of p21 to inhibit the function of this complex is dependent on interactions with both cyclin and cdk2 molecules. This was substantiated by studies with intact cells. P21 mutants that are impaired in their ability to disrupt the cellular E2F-pl30-cyclin-cdk2 complex are also shown to be maximally impaired in the ability to repress E2F-regulated transcription.

ISSN:1044-5498    

DOI:10.1089/dna.1998.17.9

年代:1998

数据来源: MAL

摘要:

Interleukin-1-beta (IL-1β) is a significant mediator in the inflammation process. Although the human IL-1β genomic sequence has been known for several years, our understanding of its molecular regulation of transcription remains incomplete. We are reporting a new transcription initiation element that is located within intron 1 and exon 2 of the human IL-1β gene. Different lengths of the human IL-1β gene fragment (-685 to +550) were cloned upstream from a chloramphenical acetyltransferase (CAT) gene to make the IL-1β promoter/CAT reporter constructs. Transient CAT expression with these constructs in the human monocytic leukemia cell line THP1 illustrates an important positive regulatory element exists within the region from +387 to +550. Using electromobility shift assays and by DNase I footprinting analysis, we identified three nuclear factor binding sites (+448 to +502, +513 to +531, and +539 to +548). Functional studies show that CAT production is undetectable when the 19 bp region (+513 to +531) is removed, and CAT production is diminished when the 10-bp region (+539 to +548) is deleted. The region containing these sites is likely to initiate a new transcript starting at +559 of exon 2. This second transcript of the IL-1β gene shares the same reading frame with the previously recognized cDNA trans

ISSN:1044-5498    

DOI:10.1089/dna.1998.17.19

年代:1998

数据来源: MAL

摘要:

The activation of H-plk (Human-proviral linked Krüppel), a human Krüppel-related zinc finger gene in organs such as placenta, adrenal cortex, and testis, is probably due to insertion of an endogenous retrovirus, ERV3, upstream of the gene. Several differently spliced transcripts originate from this locus, e.g., a transcript encoding the retroviral envelope protein and a few differentially spliced transcripts encoding both theenvand the zinc finger protein. During a screening for zinc finger proteins expressed during monocyte differentiation, two H-plk encoding cDNA clones were isolated from the human monoblast cell line U-937. Northern blot analysis of a panel of human hematopoietic cell lines showed high levels of constitutive expression of this zinc finger transcript in two monocytic cell lines (U-937 and THP-1) but not in any of the other cell lines or tissues tested. In addition, the H-plk transcript was upregulated by the phorbolester PMA in U-937 and in an additional monocytic cell line, MonoMac 6. Genomic Southern blot analysis of a panel of hematopoietic cell lines, after cleavage with the methylation sensitive enzymeXhoI, led to the detection of tissue specific demethylation in all three monocytic cell lines. TheXhoI site was mapped to a position just downstream of the regulatory region of the endogenous retrovirus. By analysis of the U-937 cell line with two additional restriction enzymes,NarI andSmaI, the demethylation was shown to affect at least three independent CpG dinucleotides in this region of the gene. In summary, the present data provide evidence for specific demethylation of this genomic region, in cells of monocytic origin, resulting in enhanced transcription of the genetic regions derived from both theenvregion of the retrovirus and the Krüppel-related zinc finger ge

ISSN:1044-5498    

DOI:10.1089/dna.1998.17.27

年代:1998

数据来源: MAL

摘要:

The ratCYP3Asubfamily of cytochrome P450 consists of steroid- and drug-metabolizing enzymes inducible by pregnenolone 16α-carbonitrile and by supra-physiological doses of dexamethasone. The induction ofCYP3Aby dexamethasone has been proposed to be mediated by a mechanism distinct from the glucocorticoid receptor mediated response. However, a synergistic induction ofCYP3Ahas been observed with physiological doses of glucocorticoids and otherCYP3Ainducers.We have identified the presence of a glucocorticoid-responsive element in theCYP3A1/IGC2gene that mediates the induction with physiological doses of glucocorticoids. A 219-bp dexamethasone responsive fragment of theCYP3A1/IGC2gene localized at -2100/-1882 bp upstream of the transcription initiation site was identified in transfection experiments with HepG2 cells. Maximum induction was achieved with 50-100 nM dexamethasone. DNase I footprinting analysis revealed two glucocorticoid receptor-protected sequences in the 5′ flank of theCYP3A1/IGC2gene. Point mutations in footprint I (-1982/-1960-bp) completely abolished binding and transcription activation whereas a mutation in footprint II (-2001/-1986-bp) only decreased the binding and had no effect on transcription activation. These results led to the conclusion that the glucocorticoid response element present in footprint I mediated the dexamethasone response in transfection experiments with HepG2 cells. Pregnenolone 16α-carbonitrile failed to induce any transcriptional effect mediated by this response element in the HepG2 ce

ISSN:1044-5498    

DOI:10.1089/dna.1998.17.39

年代:1998

数据来源: MAL

摘要:

Insulin-like growth factor binding protein 4 (IGFBP-4) is known as a potent inhibitor of IGFs action in various cell types. In this study, the mouse IGFBP-4 gene 5′ flanking region, the IGFBP-4 mRNA expression, and the IGFBP-4s intracellular transport were investigated. The regulatory region exhibits all elements typical for an eukaryotic TATA element containing promoter and was found to also contain functional elements to direct transcriptional activation of alucreporter gene construct that gradually decreased by 5′ unidirectional deletions. Responsiveness of the IGFBP-4 promoter activity was tested with thyroid hormone and found only within extended constructs but not when a potential TRα1-binding site had been deleted. By using exon specific probes, we observed a varying expression pattern of IGFBP-4 transcripts in three rodent cell lines. Surprisingly, mouse fibroblastic NIH/3T3 cells displayed exclusively about a 2.0-kb transcript apparently lacking the IGFBP-4 mRNA 5′ region. Studies on the intracellular transport by establishment of an IGFBP4/green fluorescent protein (GFP) fusion protein clearly demonstrate that IGFBP-4 is transported continuously along the intracellular secretory pathway and is excluded from other intracellular compartments. The description of the genomic IGFBP-4 region in the mouse now opens new perspectives for further clarification of the role of IGFBP-4 in growth and devel

ISSN:1044-5498    

DOI:10.1089/dna.1998.17.51

年代:1998

数据来源: MAL

摘要:

TheGOS19-1/MIP1α andGOS19-2/MIP1α genes locate to human chromosomes 17q and encode similar copies of the β-chemokine GOS19/MIP1α. TheGOS19-3gene, present in 1 in 4 humans, is a 5′ truncated version ofGOS19-2; a CpG island-containing upstream sequence (CpG-US), rich in potential transcriptional activation motifs, replaces much of the first intron and the first exon. Sequences hybridizing with theCpG-USsequence, normally exist in all human genomes. Thus, it appears that there has been recombination between a duplicatedGOS19gene and a duplicatedCpG-US-like sequence. We have isolated sequences hybridizing with theCpG-USsequence from a human genomic library in bacteriophage lambda. Restriction mapping and sequencing shows aCpG-US-like sequence ̃8 kb downstream ofGOS19-2(hence, namedCpG-DSsequence). The sequence is contiguous with aTRE17oncogene-associated sequence (GenBank locus HSTRE175). Members of theTRE17family are known to locate to chromosome 17q (Onnoet al., 1993b), and have sequence characteristics suggestive of positive Darwinian selection. Linkage with a TRE17 oncogene may have arisen by recombination and imply no functional relationship. However, it is possible that theCpG-DSmay normally regulateTRE17expression. PCR and sequencing studies indicate the close proximity of other chemokine-related sequences in the 17q11.2

ISSN:1044-5498    

DOI:10.1089/dna.1998.17.61

年代:1998

数据来源: MAL

摘要:

The round-spotted pufferfishTetraodon fluviatilishas a genome size of 380 Mb which is slightly smaller than that of another pufferfishFugu rubripes rubripes (Fugu). Due to its compact genome and small introns,Fuguhas been introduced as a model for genome studies. Recently, the round-spotted pufferfish has also been proposed as a new model for genome studies because of the ease in obtaining material and high-sequence homology to that ofFugu. In this study, we have cloned and characterized thesnf5and set genes from the round-spotted pufferfish. Thesnf5gene is composed of 9 exons spanning about 2.9 kb whereas thesetgene consists of 8 exons spanning about 2.7 kb. They are linked in a tail-to-tail manner with an intergenic region of about 6.5 kb. So far, the genomic structures of humansnf5andsetgenes are unknown. Based on our data, the pufferfish SNF5 and SET display high amino acid sequence identity (>90%) with the respective human genes. By primer extension and sequence analysis, we found that putative promoter region of thesnf5gene contains a typical TATA box and numerous potential binding sites for transcription factors including AP1, AP2, AP3, c-Myb, HNF-5, and NF-IL6. As for thesetgene, its promoter region does not have any TATA or CCAAT motif and contains a few potential binding sites for transcriptional factors such as c-Myb and gamma-IRE. When these promoter regions were placed upstream of the CAT reporter gene and transfected into a carp CF cell line, the 5′-upstream 1.6-kb DNA fragment of thesnf5gene displayed stronger promoter activity, approximately three-fold higher than that of the 5′-upstream 1.3 kb DNA fragment of thesetgene. By transient expression and immunofluorescent staining, we also showed that the pufferfish SNF5 and SET are nuclear proteins, consistent with their postulated roles as transcriptional fact

ISSN:1044-5498    

DOI:10.1089/dna.1998.17.69

年代:1998

数据来源: MAL

摘要:

We have used a polymerase chain reaction strategy to isolate a metallothionein (MT) cDNA from the amphibianAmbystoma mexicanum(axolotl). This cDNA is 875-bp long and encodes a 60 amino acid protein, AmMT, typical for family 1 MTs. It contains 20 cysteine (Cys) residues that can be aligned with those of other vertebrate MTs. The overall structure of the protein is unique among vertebrates in having only two amino acid residues before the first Cys at the amino-terminal end. Northern analyses showed thatAmMTis expressed throughout embryogenesis, giving rise to three mRNA species of 650, 750, and 1,600 nucleotides (nt). The 750 and 1,600 nt transcripts appear to result from differential use of polyadenylation signals, whereas the 650 nt RNA could arise from deadenylation of the 750-nt transcript. Both the 750- and 1,600-nt RNAs were presented in embryos before the mid-blastula transition (MBT). After the MBT, the 750-nt RNA was replaced by the 650-nt RNA which was gradually degraded to undetectable levels in post-neurulation embryos. Levels of the 1,600-nt transcript increased at gastrulation and reach a maximum in Stage 30 embryos. In adult animals, levels of the 750-nt RNA were high in liver and testes, and very low in lung, gut, skin, and oviducts, whereas levels of the 1,600-nt transcript were similar and moderately elevated in all tissues examined. In contrast, inXenopus laevis, Northern analysis did not detect XIMT-A mRNA in embryos before late neurulation (Stage 24). XIMT-A mRNA levels then increased sharply in Stage 36 hatched embryos at levels similar to those found in adult livers. These results show thatAmMTpresents a unique expression pattern among metazoans being transcribed as two transcripts differing in the length of their 3′ untranslated regions, the levels of which vary during embryogenesis and in adult tissue

ISSN:1044-5498    

DOI:10.1089/dna.1998.17.83

年代:1998

数据来源: MAL

摘要:

The gene encoding turkey Pit-1/GHF-1 (tPit-1) spans approximately 12 kilobases (kb) and consists of 7 exons. One exon, which is located between exons 2 and 3, is designated exon 2a and codes for 38 amino acids not found in mammalian Pit-1. Because all tPit-1 variants contain exon 2a, they are denoted with an asterisk (*) to distinguish them from comparable mammalian Pit-1s. Three tPit-1 variants are generated by alternative splicing and transcription initiation. Splicing of exon 1 to an alternative acceptor splice site in exon 2 results in a 28 amino acid insertion in tPit-1β* relative to tPit-1*. A transcript unique to the turkey has been identified by RT-PCR and RNase mapping. This transcript, designated tPit-1W*, arises following transcription initiation upstream of the alternative acceptor splice site in exon 2. In turkey pituitary, the mRNA for the tPit-1* variant is the most abundant, the tPit-1W* variant is intermediate, and the tPit-1β* variant is the least abundan

ISSN:1044-5498    

DOI:10.1089/dna.1998.17.93

年代:1998

数据来源: MAL