Inhibition of HMGI-C protein synthesis suppresses retrovirally induced neoplastic transformation of rat thyroid cells

Elevated expression of the three high-mobility group I (HMGI) proteins (HMGI, HMGY, and HMGI-C) has previously been correlated with the presence of a highly malignant phenotype in epithelial and fibroblastic rat thyroid cells and in experimental thyroid, lung, mammary, and skin carcinomas. Northern (RNA) blot and run-on analyses demonstrated that the induction of HMGI genes in transformed thyroid cells occurs at the transcriptional level. An antisense methodology to block HMGI-C protein synthesis was then used to analyze the role of this protein in the process of thyroid cell transformation. Transfection of an antisense construct for the HMGI-C cDNA into normal thyroid cells, followed by infection with transforming myeloproliferative sarcoma virus or Kirsten murine sarcoma virus, generated cell lines that expressed significant levels of the retroviral transforming oncogenes v-mos or v-ras-Ki and removed the dependency on thyroid-stimulating hormones. However, in contrast with untransfected cells or cells transfected with the sense construct, those containing the antisense construct did not demonstrate the appearance of any malignant phenotypic markers (growth in soft agar and tumorigenicity in athymic mice). A great reduction of the HMGI-C protein levels and the absence of the HMGI(Y) proteins was observed in the HMGI-C antisense-transfected, virally infected cells. Therefore, the HMGI-C protein seems to play a key role in the transformation of these thyroid cells.

Identification of a novel vertebrate homeobox gene expressed in haematopoietic cells

This paper describes the characterisation of a novel chicken homeobox gene, Prh, whose encoded homeodomain sequence differs significantly from those of other factors which have been described. As expected, a portion of the encoded protein, containing the homeodomain, is capable of sequence-specific DNA-binding. Outside the homeodomain, Prh, possesses an N-terminal region extremely rich in proline residues and a C-terminal acidic portion, either of which may function as transcription regulatory domains. Since, among the chicken tissues tested, its transcription is restricted to haematopoietic cells, lung and liver, it may function in tissue-specific patterns of gene regulation. Human and murine Prh homologues have also been identified; so it is likely that such genes are a general feature of vertebrate genomes.

cDNA cloning of the HMGI-C phosphoprotein, a nuclear protein associated with neoplastic and undifferentiated phenotypes

The HMGI-C protein is a nuclear phosphoprotein expressed at high levels in transformed cells. The cDNA encoding the mouse protein has been isolated and the sequence of the encoded protein shows that it is related to the HMGY and I proteins, proteins which bind in the minor groove of DNA containing stretches of A and T. The HMGI-C protein has three short highly basic domains, an acidic C-terminal domain, and potential CDC2/p34 and casein kinase II phosphorylation sites. Analysis of mRNA levels demonstrate that the HMGI-C gene is not expressed in a variety of mouse tissues but is expressed in Lewis lung carcinoma cells.

HMGI-C and HMGI(Y) immunoreactivity correlates with cytogenetic abnormalities in lipomas, pulmonary chondroid hamartomas, endometrial polyps, and uterine leiomyomas and is compatible with rearrangement of the HMGI-C and HMGI(Y) genes

High-mobility group (HMG) proteins are nonhistone nuclear proteins that play an important role in the regulation of chromatin structure and function. HMGI-C and HMGI(Y) are members of the HMGI family of HMG proteins, and their expression in adult tissues generally correlates with malignant tumor phenotypes. However, HMGI-C and HMGI(Y) dysregulation as a result of specific rearrangements involving 12q15 and 6p21, the respective chromosomal sites in which the HMGI-C and HMGI(Y) genes are located, is also identified in a variety of common benign mesenchymal tumors, such as lipomas and uterine leiomyomata. The general prevalence of HMGI-C and HMGI(Y) protein expression and its correlation with chromosomal alterations in these benign tumors are unknown. We analyzed 95 human tumors (20 lipomas, 21 pulmonary chondroid hamartomas, 26 uterine leiomyomata, and 28 endometrial polyps) representing a selection of the benign lesions in which karyotypic alterations involving the chromosomal regions 12q15 and 6p21 are frequently detected. All cases were successfully karyotyped and some of them analyzed by fluorescent in situ hybridization with probes spanning the HMGI-C and HMGI(Y) genes. The results of this study demonstrate that expression of HMGI-C or HMGI(Y) is a common occurrence in lipomas, pulmonary chondroid hamartomas, leiomyomata, and endometrial polyps; that it correlates with 12q15 and 6p21 chromosomal alterations (p < 0.001); and that it is compatible with rearrangement of the HMGI-C and HMGI(Y) genes. The expression pattern and cellular localization of the immunoreactivity support the view that in biphasic lesions composed of a mixture of both stromal and epithelial cells, such as pulmonary chondroid hamartoma and endometrial polyps, the mesenchymal component is the site of the HMGI genetic alterations.

Elevated levels of a specific class of nuclear phosphoproteins in cells transformed with v-ras and v-mos oncogenes and by cotransfection with c-myc and polyoma middle T genes

Transformation of a rat thyroid epithelial cell line (FRTL5-C12) with Kirsten and Harvey murine sarcoma viruses (carrying the ras oncogenes) results in elevated levels of three perchloric acid-soluble nuclear phosphoproteins. These three proteins are also induced to high levels in the PC-C13 thyroid epithelial cell line when transformed by the myeloproliferative sarcoma virus (carrying the v-mos oncogene) and when transformed by transfection with the c-myc proto-oncogene followed by infection with the polyoma leukaemia virus (PyMuLV) carry the polyoma middle T antigen gene. Neither c-myc or PyMuLV alone induced high levels of the three nuclear proteins. Untransformed thyroid fibroblasts have high levels of two of the three proteins and can be transformed by PyMuLV alone resulting in the appearance of the third protein. Transformation with Harvey sarcoma virus also results in the induction of the third protein. The three phosphoproteins have been purified by h.p.l.c. and shown to be related to the HeLa protein HMGI already described. The results of these studies indicate that elevated levels of these HMGI-like proteins are associated with neoplastic transformation and/or with an undifferentiated phenotype.

Analysis of the HMGI nuclear proteins in mouse neoplastic cells induced by different procedures

Four malignant tumors induced in mouse by different experimental procedures were compared as regards their high-mobility-group (HMG) proteins. All tumors showed the complete set of three HMG proteins which we call HMGI-C, I-D, and I-E. The presence of the three HMGI proteins is a characteristic of the transformed phenotype regardless of whether the tumor was chemically, virally, or spontaneously derived. However, the level of expression of the HMGI proteins is not constant in the four tumors. Using reverse-phase HPLC, the individual HMGI proteins were isolated from the spontaneously derived tumor (Lewis lung carcinoma) and shown by amino acid analysis to be similar to those previously obtained from a tumor grown in nude mice by inoculation of in vitro-transformed cells.

Role of the high mobility group A proteins in human lipomas

The HMGA family is comprised of four proteins: HMGA1a, HMGA1b, HMGA1c and HMGA2. The first three proteins are products of the same gene, HMGA1, generated through an alternative splicing mechanism. The HMGA proteins are involved in the regulation of chromatin structure and HMGA DNA-binding sites have been identified in functional regions of many gene promoters. Rearrangements of the HMGA2 gene have been frequently detected in human benign tumors of mesenchymal origin including lipomas. 12q13-15 chromosomal translocations involving the HMGA2 gene locus, account for these rearrangements. The HMGA proteins have three AT-hook domains and an acidic C-terminal tail. The HMGA2 modifications consist in the loss of the C-terminal tail and fusion with ectopic sequences. A pivotal role of the HMGA2 rearrangements in the process of lipomagenesis is suggested by experiments showing that transgenic mice carrying a truncated HMGA2 gene showed a giant phenotype together with abdominal/pelvic lipomatosis. As HMGA2 null mice showed a great reduction in fat tissue, a positive role of the HMGA2 gene in adipocytic cell proliferation is proposed. More recently, similar alterations of the HMGA1 gene have been described. As the block of the HMGA1 protein synthesis induces an increase in growth rate of the pre-adipocytic cell line 3T3-L1, we suggest a negative role of the HMGA1 proteins in adipocytic cell growth and, therefore, we propose that adipocytic cell growth derives from the balance of the HMGA1 and HMGA2 protein functions.

Studies on the role and mode of operation of the very-lysine-rich histone H1 (F1) in eukaryote chromatin. Histone H1 in chromatin and in H1 - DNA complexes

The nuclear magnetic resonance (NMR) spectrum of chromatin at ionic strengths below about 0.5 M may be attributed solely to its histone H1 component. The effect of various ions and urea on the complex has been investigated using NMR and confirm that the contraction of the complex on increase of ionic strength is largely due to electrostatic interactions. A detailed study of the H1 - DNA complex has also been undertaken. The behaviour of H1 in the two cases is virtually identical, implying that in chromatin the H1 is complexed with the DNA rather than with the other histones. Microcalorimetric measurements reveal that the binding of H1 to DNA is athermic or involves a heat of reaction which is very small indeed.

High mobility group HMGI(Y) protein expression in human colorectal hyperplastic and neoplastic diseases

HMGI(Y) proteins are overexpressed in experimental and human malignancies, including colon, prostate and thyroid carcinomas. To determine at which step of the carcinogenic process HMGI(Y) induction occurs, we analysed the expression of the HMGI(Y) proteins in hyperplastic, preneoplastic and neoplastic tissues of colorectal origin by immunohistochemistry. All the colorectal carcinomas were HMGI(Y)-positive, whereas no expression was detected in normal colon mucosa tissue. HMGI(Y) expression in adenomas was closely correlated with the degree of cellular atypia. Only 2 of the 18 non-neoplastic polyps tested were HMGI(Y)-positive. These data indicate that HMGI(Y) protein induction is associated with the early stages of neoplastic transformation of colon cells and only rarely with colon cell hyperproliferation.

Comparison of multiple forms of the high mobility group I proteins in rodent and human cells. Identification of the human high mobility group I-C protein

The class I of the high mobility group (HMG) proteins is formed by phosphoproteins which are associated with AT-rich DNA sequences in the nucleus. Three HMGI proteins have previously been described in proliferating rodent cells (HMG Y, HMG I and HMGI-C). All three proteins exhibit microheterogeneity. The microheterogeneity of mouse HMG Y has been investigated in detail and shown to be due to phosphorylation of the protein which is sensitive to alkaline-phosphatase treatment. HMG I is similarly modified. Human cells have up to now only been found to contain HMG Y and HMG I. A search for the third protein, HMGI-C, in human cells was carried out and the protein was found in a hepatoma cell line, but not in normal or transformed T-cells. This HMGI-C protein was found to be modified by phosphorylation, part of which was found to be phosphatase insensitive. An unexpected additional finding in this study was that human cells contain two HMG17 proteins which differ in their N-terminal primary sequences.

High-mobility-group (HMG) proteins and histone H1 subtypes expression in normal and tumor tissues of mouse

Exhaustive extraction of mouse tissues with perchloric acid has been used together with reverse-phase HPLC and electrophoresis to quantify the amounts of chromosomal proteins HMG17, HMG14 and HMGI, relative to histone H1. Normal lung and thymus contain approximately 3% HMG17/HMG14 but only approximately 2% HMGI. In tumor tissues (Lewis lung carcinoma and lymphoma NQ35), the amount of HMG17/HMG14 is not greatly altered but HMGI levels rise considerably, reaching 10% in Lewis lung carcinoma. HMGI synthesis does not replace HMG17/HMG14 proteins, suggesting that HMGI proteins contribute to the structure of chromatin regions in a manner distinct from those of HMG17/HMG14. Ion-spray mass spectrometry has been used to determine the molecular masses of H1 subtypes from the same four mouse tissues. In addition to the six known species H1 zero, H1a, H1b, H1c, H1d and H1e, a newly defined subtype of mass 21,756 Da from Lewis lung carcinoma, named H1L was identified. Several phosphorylated H1 subtypes have also been defined by mass spectrometry. The combined use of reverse-phase HPLC and electrophoresis permitted quantification of these seven histone H1 subtypes in the four mouse tissues. Increased phosphorylation of H1 subtypes in tumors parallels the phosphorylation of HMGI proteins which are present in great amounts, showing that both are involved as post-translational-modified forms in the structure of the chromatin of neoplastic systems.

Expression and cDNA cloning of human HMGI-C phosphoprotein

The HMGI family contains three members: I, Y and I-C. HMGI and HMGY are alternative splicings of the same gene and are essential transcription factors at several genetic loci. HMGI-C is transcribed from a different gene and is observed only in highly transformed cells. This work shows that human I-C is present in a more restricted range of cell types than I/Y and is absent from hemopoietic cells, as noted for mouse I-C. However, high expression in a human hepatoma line allowed the cloning of the cDNA and 812 bp of 5'-untranslated, 330 bp of coding and 58 bp of 3'-untranslated DNA were sequenced. The open reading frame showed 4 amino acid substitutions and one additional amino acid when compared to mouse I-C, none of them in the basic DNA binding motifs.

A link between apoptosis and degree of phosphorylation of high mobility group A1a protein in leukemic cells

Nuclear phosphoprotein HMGA1a, high mobility group A1a, (previously HMGI) has been investigated during apoptosis. A change in the degree of phosphorylation of HMGA1a has been observed during apoptosis induced in four leukemic cell lines (HL60, K562, NB4, and U937) by drugs (etoposide, camptothecin) or herpes simplex virus type-1. Both hyper-phosphorylation and de-phosphorylation of HMGA1a have been ascertained by liquid chromatography-mass spectrometry. Hyper-phosphorylation (at least five phosphate groups/HMGA1a molecule) occurs at the early apoptotic stages and is probably related to HMGA1a displacement from DNA and chromatin release from the nuclear scaffold. De-phosphorylation (one phosphate or no phosphate groups/HMGA1a molecule) accompanies the later formation of highly condensed chromatin in the apoptotic bodies. We report for the first time a direct link between the degree of phosphorylation of HMGA1a protein and apoptosis according to a process that involves the entire amount of HMGA1a present in the cells and, consequently, whole chromatin. At the same time we report that variously phosphorylated forms of HMGA1a protein are also mono-methylated.

Characterization of intermediate compounds formed upon photoinduced degradation of quinolones by high-performance liquid chromatography/high-resolution multiple-stage mass spectrometry

The paper deals with the photocatalytic transformation of two antibacterial agents, ofloxacin and ciprofloxacin, under simulated solar irradiation using titanium dioxide as photocatalyst. The investigation involved monitoring decomposition of the drugs, identifying intermediate compounds, assessing mineralization, and evaluating the toxicity of drug derivatives. High-resolution mass spectrometry was employed to assess evolution of the photocatalyzed process over time. Respectively 15 and 8 main species were identified after transformation of ofloxacin and ciprofloxacin. Through the full analysis of MS and MSn spectra and a comparison with parent drug fragmentation pathways, the different isomers were characterized. In the ofloxacin molecule, the initial transformation attacks are confined to the piperazine moiety and to the methyl groups, while the fluoroquinolone core is unmodified. Conversely, ciprofloxacin degradation involves two parts of the molecule: the piperazinic moiety and the quinolone moiety. All these intermediates are easily degraded and by 4 h mineralization is complete. Toxicity assays using Vibrio fischeri prove that neither ciprofloxacin nor its intermediates exhibit acute toxicity. In ofloxacin the secondary degradation products exhibit toxicity; a correlation exists between the evolution of the intermediate compounds and the toxicity connected to them.

Fluorescence of buried tyrosine residues in proteins

Histone H1 contains only one tyrosine and no tryptophan. The intrinsic fluorescence of the tyrosine rises by about 400% as the protein folds from a random coil to a globular structure (Giancotti, V., Fonda, M. and Crane-Robinson, C. (1977) Biophys. Chem. 6, 379-383). Measurements of external quenching by a large variety of quenchers shows very much reduced quenching in the folded state as compared to the disordered. It is concluded that the tyrosine is a buried residue. This is supported by the observation that the fluorescence of modified amino-tyrosyl H1 is similar to that of buried tyrosines in ribonuclease. The classification of tyrosine fluorescence in tryptophan-free proteins (Cowgill, R.W. (1976) in Biochemical Fluorescence Concepts, Vol. 2 to include the case of residues buried in a hydrophobic environment and having a relative quantum yield RTyr, greater than unity.

Reduction of risk factors for cardiovascular diseases in morbid-obese patients following biliary-intestinal bypass: 3 years' follow-up

BACKGROUND

Obese patients are often affected by hypertension, dyslipidaemia, impaired glucose metabolism, and suffer from cardiovascular disease (CVD), related to the characteristic metabolic alterations.

AIM OF THE STUDY

To evaluate reduction of risk factors for CVDs in morbid-obese patients (body mass index (BMI)>40 kg/m2) after weight loss upon bariatric surgery intervention of biliary-intestinal bypass.

SUBJECTS

45 (17 men, 28 women) morbid-obese patients (age: 19-49 y, BMI>40 kg/m2). All patients were selected on the basis of medical history, physical and biochemical evaluation and of psychiatric tests, which were performed on all individuals admitted to our Day Hospital to verify the safety of surgical intervention.

MEASUREMENTS

Body weight, body composition (by dual X-ray absorptiometry, DXA), blood pressure, lipid profile, fibrinogen and glucose metabolism were monitored at baseline and 1, 3, 6, 9, 12, 24 and 36 months after surgery.

RESULTS

A significant and persistent weight loss was present in all patients at the end of the 3 y follow-up period (P<0.001), with a progressive reduction of total and trunk fat mass as evaluated by means of DXA. Additionally, a parallel significant reduction in systolic (P<0.001) and diastolic (P<0.001) blood pressure was observed. Total and LDL cholesterol were significantly reduced (P<0.001), while HDL showed no modifications; triglycerides declined progressively during the 3 y follow-up (P<0.001). Fibrinogen decreased from 364.5+/-82.4 to 266.4+/-45.7 mg/dl at the end of the period (P<0.001). Fasting glucose levels and glucose levels 120 min after an oral glucose tolerance test were reduced from 95.1+/-20.3 to 78.6+/-9.1 mg/dl (P<0.001) and from 116.9+/-34.7 to 77.6+/-15.5 mg/dl (P<0.001), respectively, at baseline and at the end of the study. Moreover, fasting insulin decreased from 30.0+/-20.4 to 8.6+/-2.9 microUI/ml (P<0.001) after 3 y, while insulin levels after (120 min) oral glucose load decreased from 105.5+/-61.5 to 12.0+/-6.0 microUI/ml (P<0.001).

CONCLUSION

Our results show that biliary-intestinal bypass may represent a valid and alternative therapeutic approach in patients with morbid obesity since it induces a significant and stable reduction of body weight and obesity-related risk factors for CVD.

Secondary and tertiary structural differences between histone H1 molecules from calf thymus and sea-urchin (Sphaerechinus granularis) sperm

Tryptic digestion of histone H1 from the sperm of the sea urchin Sphaerechinus granularis leaves a limiting peptide of approx. 80 residues that is of similar size to the limit peptide from calf thymus H1 or chicken erythrocyte H5. The S. granularis limit peptide folds to form tertiary structure similar to that of the intact parent histone H1 (shown by n.m.r. spectra), but the helical content is decreased by the digestion from 64 residues to 28. In contrast, intact calf thymus H1 and chicken erythrocyte H5 histones have only about 28 helical residues, which are preserved in their limit peptides. The extra helix in S. granularis is shown to be rapidly digested away by trypsin, and its location in histone H1 is discussed. A possible relationship of this structural feature to the length of linker DNA is proposed.

Proteins from the sperm of the bivalve mollusc Ensis minor. Co-existence of histones and a protamine-like protein

Analysis of the total protein of the mature sperm of the bivalve mollusc Ensis minor (razor shell) using gel electrophoresis, amino acid analysis, nuclear magnetic resonance, circular dichroism and trypsin digestion, show it to contain all five histones plus a protamine-like protein. The histones H3, H4 and probably H2A are similar to those from calf thymus or sea urchin sperm, but the putative H2B appears to have a very high molecular mass (about 20 kDa). The histone H1 molecule is unusual, having little or no proline and 8-10 residues of histidine. The protamine-like species is rich in both lysine as well as arginine and is of much higher molecular mass than fish sperm protamines. Nucleosomes containing the four core histones have been prepared and the nucleosomal repeat shown to be 200 +/- 5 base pairs. Checks for the absence of contaminating cells reinforce the conclusion that a histone-containing nucleosomal structure co-exists with a protamine-like protein in this sperm chromatin.

Histone modification in early and late Drosophila embryos

Levels of histone acetylation and phosphorylation have been contrasted in two developmental states of Drosophila melanogaster. The 0-2 h nuclei of the syncitial blastula are characterized by rapid mitoses and DNA replication, but there is very little transcription. In the 18 h embryo there is considerable transcription and the mitotic rate is much slower. It has been found that (1) histone H1 from 2h nuclei is not highly phosphorylated. This observation is not in accord with the view that H1 hyperphosphorylation is essential to mitosis, but is compatible with the hypothesis that H1 phosphorylation in Drosophila species is related to heterochromatization. (2) Histone H4 from 2 h embryos shows high levels of the diacetyl form (H4-Ac2), which is principally outside the nucleus. This accords with the hypothesis that H4-Ac2 is the form in which H4 is deposited on to newly replicated DNA and shows that H4 acetylation is linked not only to transcription. (3) Histone H3 acetylation is similar in 2h and in 18h embryos. As with H4, this acetylation probably correlates with chromatin assembly and is not transcription-related. (4) Histone H2B carries no modification in 2h or in 18h embryos, and H2A shows a single modification in 2h embryos and two in 18 h embryos. H2B modification is thus not essential either in mitosis or replication, whereas H2A modification is important in one or both processes. (5) The nucleosomal protein D2 is equally present in 2h and 18 h embryos.

High mobility group I proteins interfere with the homeodomains binding to DNA

Homeodomains (HDs) constitute the DNA binding domain of several transcription factors that control cell differentiation and development in a wide variety of organisms. Most HDs recognize sequences that contain a 5'-TAAT-3' core motif. However, the DNA binding specificity of HD-containing proteins does not solely determine their biological effects, and other molecular mechanisms should be responsible for their ultimate functional activity. Interference by other factors in the HD/DNA interaction could be one of the processes by which HD-containing proteins achieve the functional complexity required for their effects on the expression of target genes. Using gel-retardation assay, we demonstrate that two members of the high mobility group I (HMGI) family of nuclear proteins (HMGI-C and HMGY) can bind to a subset of HD target sequences and inhibit HDs from binding to the same sequences. The inhibition of the HD/DNA interaction occurs while incubating HMGI-C with DNA either before or after the addition of the HD. The reduced half-life of the HD.DNA complex in the presence of HMGI-C, and the shift observed in the CD spectra recorded upon HMGI-C binding to DNA, strongly suggest that structural modifications of the DNA are responsible for the inhibition of the HD.DNA complex formation. Moreover, by co-transfection experiments we provide evidence that this inhibition can occur also in vivo. The data reported here would suggest that HMGI proteins may be potential regulators of the function of HD-containing proteins and that they are able to interfere with the access of the HD to their target genes.