Chromatin compaction and cell death by high molecular weight FGF-2 depend on its nuclear localization, intracrine ERK activation, and engagement of mitochondria

Fibroblast growth factor 2 (FGF-2) is produced as CUG-initiated, 22-34 kDa or AUG-initiated 18 kDa isoforms (hi- and lo-FGF-2, respectively), with potentially distinct functions. We report that expression of hi-FGF-2 in HEK293 cells elicited chromatin compaction preceding cell death with apoptotic features. Nuclear localization of the intact protein was required as expression of a non-nuclear hi-FGF-2 mutant failed to elicit chromatin compaction. Equally ineffective, despite nuclear localization, was the over-expression of the 18 kDa core sequence (lo-FGF-2). Chromatin compaction by hi-FGF-2 was accompanied by increased cytosolic cytochrome C, and was attenuated either by over-expression of Bcl-2 or by a peptide inhibitor of the pro-apoptotic protein Bax. In addition hi-FGF-2 elicited sustained activation of total and nuclear extracellular signal regulated kinase (ERK1/2) by an intracrine route, as it was not prevented by neutralizing anti-FGF-2 antibodies. Inhibition of the ERK1/2 activating pathway by dominant negative upstream activating kinase, or by PD 98059, prevented chromatin compaction by hi-FGF-2. ERK1/2 activation was not affected by the Bax-inhibiting peptide suggesting that it occurred upstream of mitochondrial involvement. We conclude that the hi-FGF-2-induced chromatin compaction and cell death requires its nuclear localization, intracrine ERK1/2 activation and mitochondrial engagement.     

Human chorionic somatomammotropin and growth hormone gene expression in rat pituitary tumour cells is dependent on proximal promoter sequences.

Human placental chorionic somatomammotropin (hCS-A or hCS-B) and pituitary growth hormone (hGH-N) are related by structure and function. The hCS-A gene is expressed in rat pituitary tumour (GC) cells after gene transfer. Deletion of hCS-A 5'-flanking DNA reveals repressor activity upstream of nucleotide -132, and a region essential for expression in GC cells between nucleotides -94 and -61. The sequences in this region differ from the equivalent hGH-N gene DNA by one nucleotide, and include the binding site (-92 to -65) for a pituitary-specific factor (GHF-1), required for hGH-N expression in GC cells. Exchange of hGH-N with hCS-A gene DNA in this region maintains expression in GC cells. By contrast, modification of these sequences blocks expression. These data indicate that proximal promoter sequences, equivalent to those bound by GHF-1 on the hGH-N gene, are required for hCS-A expression in GC cells.     

Expression of fibroblast growth factor receptor-1 in rat heart H9c2 myoblasts increases cell proliferation

Aspergillus fumigatus is a highly pathogenic fungus causing a wide spectrum of diseases in immunocompromised as well as immunocompetent hosts. The present work was undertaken to evaluate the cytotoxic nature of fractionated antigens of A. fumigatus against the mammalian cell lines (J774, RAW, CHO and L929). An enriched protein antigenic fraction of A. fumigatus was subjected to con A Sepharose and phenyl Sepharose chromatography. Antigenic fractions, ConAub (conA unbound) and PSC III (fraction III of phenyl Sepharose column) containing low mw antigens showed higher cytotoxicity as compared to other antigenic fractions. PSC III was further purified on HPLC resulting in an 18 kDa homogeneous protein. The purified protein showed high ELISA absorbance values for specific IgG and IgE antibodies in sera of ABPA patients. Monoclonal antibody raised against Asp fl, a major allergen/antigen of A. fumigatus recognised the purified 18 kDa by ELISA and western blot. The 18 kDa allergen/antigen or Asp fl showed similar toxicity towards all the four cell lines (macrophage and fibroblast) with an IC50 of 75 ng/ml or 4.16 nM. Reduction in toxicity of 18 kDa at low temperatures and potentiation in presence of ammonium chloride and monensin indicates mechanism of internalisation of 18 kDa in eukaryotic cells is similar to -sarcin. The present work shows that the 18 kDa allergen/antigen (Asp fl) is a major cytotoxin secreted by A. fumigatus which may play multiple roles in the pathogenesis of Aspergillosis through allergenicity, antigenicity and cytotoxicity. (Mol Cell Biochem 167: 89-97, 1997)     

An experimental evaluation of a loop versus a reference design for two-channel microarrays

MOTIVATION: Despite theoretical arguments that so-called 'loop designs' for two-channel DNA microarray experiments are more efficient, biologists continue to use 'reference designs'. We describe two sets of microarray experiments with RNA from two different biological systems (TPA-stimulated mammalian cells and Streptomyces coelicolor). In each case, both a loop and a reference design were used with the same RNA preparations with the aim of studying their relative efficiency. RESULTS: The results of these experiments show that (1) the loop design attains a much higher precision than the reference design, (2) multiplicative spot effects are a large source of variability, and if they are not accounted for in the mathematical model, for example, by taking log-ratios or including spot effects, then the model will perform poorly. The first result is reinforced by a simulation study. Practical recommendations are given on how simple loop designs can be extended to more realistic experimental designs and how standard statistical methods allow the experimentalist to use and interpret the results from loop designs in practice. AVAILABILITY: The data and R code are available at http://exgen.ma.umist.ac.uk CONTACT: veronica.vinciotti@brunel.ac.uk.