Change of hepatitis B virions (Dane particles) phosphorylation pattern by human hepatoma cell particulate fraction

Protein kinase activity has been found in hepatitis B virions (Dane particles) purified from the plasma of hepatitis B surface antigen carriers [Albin, C., and Robinson, W.S. (1980) J. Virol. 34, 297-302]. Dane particles were purified from the pooled, HBeAg-positive plasma. When this preparation was incubated with [gamma 32P]ATP in the presence of 10mM MnCl2 and 0.5% NP-40 for 15 seconds at 30 degrees C, several phosphorylated polypeptides of 20,000, 42,000, 48,000, 50,000 and 56,000 daltons were detected in sodium dodecyl sulfate-polyacrylamide gels. When the Dane particles were incubated with [gamma 32P]ATP, 10 mM MnCl2, and 0.5% NP-40 in the presence of human hepatoma cell (J-5) particulate fraction at 30 degrees C, 15 seconds, the 42,000, 48,000 and 50,000 daltons phosphorylated polypeptides were not found. When human peripheral blood lymphocytes particulate fraction was incubated with Dane particles under the same conditions, no change of Dane particle phosphorylated polypeptides was detected. Previous publications [Albin, C., and Robinson, W.S. (1980) J. Virol. 34, 297-302; Gerlich, W.H. et al. (1982) J. Virol. 42, 761-766] showed that when hepatitis B core particles purified from hepatoma tissues contained protein kinase activity, only phosphorylated polypeptide was 20,000 daltons. Our data suggested that when Dane particles were put in an environment of hepatoma cells (or tissues), the protein kinase could only phosphorylate selected polypeptides in these particles.     

Analysis of the structure and expression of the c-myc oncogene in cervical tumor and in cervical tumor-derived cell lines

The structure of the c-myc oncogene in 17 cervical tumors and patient-matched nontumor tissues from Chinese patients residing in Taiwan was analysed. In contrast to recent reports on Mexican patients, none of the samples showed rearrangements and sequence amplification in the c-myc gene. The discrepancy may be explained by different carcinogenesis mechanisms being in operation in different geographic regions. Although no structural alterations in the c-myc gene were found in seven cervical carcinoma cell lines analysed, Northern blot analysis indicated different levels of c-myc gene expression which may be related to the presence of human papillomavirus (HPV) sequence in the cell and suggests a possible c-myc-hpv interaction in some stages of the transformation process.     

Insulin-induced expression of human heat-shock protein gene hsp70

In human hepatoma cell line Hep3B/T2, the human heat-shock-inducible gene hsp70 could be induced by insulin. The dose-dependent insulin effect correlates very well with the dissociation constant of the insulin receptor, indicating that the insulin effect is mediated by the insulin receptor. The expression of hsp70 gene was neither significantly induced by growth factors of epidermal and platelet-derived growth factors, nor by tumor promoter, calcium ionophore, cAMP, and glucocorticoids. These results indicate that the induction of expression of hsp70 gene by insulin is very specific and not cell cycle-related. Furthermore, the insulin-induced expression of hsp70 gene is transient, occurring specifically from 4 to 8 h after insulin addition.     

The biological functions of low-frequency vibrations (phonons). VI. A possible dynamic mechanism of allosteric transition in antibody molecules

By means of the quasi-continuity theory developed recently [Chou, K.-C. (1983) Biochem. J. 209 , 573–580; Chou, K.-C. (1984) Biochem. J. 221 , 27–31; Chou, K.-C. (1985) Biophys. J. 48 , 289–297], the low-frequency breathing motions of the β-barrels in the 12 domains of an IgG antibody molecule have been calculated. The results are in very good agreement with the observed low-frequency peaks in the Raman spectra. Based on this, the resonant couplings among the domains located at its different regions are discussed. It turns out that some very interesting functions of antibody molecules, such as the “chelate effect” and “trigger effect” whose dynamic principle has been so far unknown, can be clearly elucidated in terms of a fundamental natural law; i.e., it is through the channel of low-frequency resonance that the “signal” (or energy) in an antibody is transmitted from one location to the other, so as to be able to induce the relevant conformational change required for operating those important biological functions. The physical picture illustrated here once again provides us with a classic example that structure and function in nature are highly harmonized.     

Thermotolerance of isolated mitochondria associated with heat shock proteins

Mitochondria isolated from 2-day-old etiolated soybean (Glycine max) seedlings which had been subjected to various heat shock treatments, i.e. (A) 28°C (2 h), (B) 38°C (2 h), (C) 38°C (2 h)-42.5°C (0.5 h), and (D) 38°C (2 h)-42.5°C (0.5 h)-28°C (4 h), were monitored for O₂ uptake using an oxygen electrode. Mitochondria isolated after all four heat shock treatments were active in O₂ consumption at 28°C in response to succinate and ADP (derived P/O ratios were 1.6, 1.7, 1.3, and 1.3, respectively.) The mitochondria from all four treatments were also active in O₂ uptake at 42.5°C. However, only mitochondria isolated after treatment (C) were tightly coupling at 42.5°C (derived ADP/O ratio was about 1.4). Combined with our earlier findings on the subcellular localization of heat shock proteins, our present data demonstrate that association of heat shock proteins with mitochondria by treatment (C) enables them to phosphorylate at 42.5°C (i.e. they become thermotolerant). Isolated mitochondria from treatment (C) and treatment (A) were compared by electron microscopy. They appeared to be very similar and no significant ultrastructural differences were noted.     

An immunofluorescence study of the effects of ultraviolet radiation on the organization of microfilaments, keratin intermediate filaments, and microtubules in human keratinocytes.

Indirect immunofluorescence microscopy has been used to investigate the ultraviolet (UV) radiation induced disruption of the organization of microfilaments, keratin intermediate filaments, and microtubules in cultured human epidermal keratinocytes. Following irradiation, concurrent changes in the organization of the three major cytoskeletal components were observed in cells incubated under low Ca2+ (0.15 mM) conditions. UV irradiation induced a dose-dependent condensation of keratin filaments into the perinuclear region. This collapse of the keratin network was accompanied by the reorganization of microfilaments into rings and a restricted distribution of microtubules, responses normally elicited by exposure to high Ca2+ (1.05 mM) medium. The UV induced alteration of the keratin network appears to disrupt the interactions between keratin and actin, permitting the reorganization of actin filaments in the absence of Ca2+ stimulation. In addition to the perinuclear condensation of keratin filaments, UV irradiation inhibits the Ca2+ induced formation of keratin alignments at the membrane of apposed cells if UV treatment precedes exposure to high Ca2+ medium. Incubation of keratinocytes in high Ca2+ medium for 24 hours prior to irradiation results in the stabilization of membrane associated keratin alignments and a reduced susceptibility of cytoplasmic keratin filaments to UV induced disruption. Unlike results from investigations with isogenic skin fibroblasts, no UV induced disassembly of microtubules was discernible in irradiated human keratinocytes.     

Tropomyosin isoforms in chicken embryo fibroblasts: purification, characterization, and changes in Rous sarcoma virus-transformed cells

Seven polypeptides (a, b, c, 1, 2, 3a, and 3b) have been previously identified as tropomyosin isoforms in chicken embryo fibroblasts (CEF) (Lin, J. J.-C., Matsumura, F., and Yamashiro-Matsumura, S., 1984, J. Cell. Biol., 98:116-127). Spots a and c had identical mobility on two-dimensional gels with the slow-migrating and fast-migrating components, respectively, of chicken gizzard tropomyosin. However, the remaining isoforms of CEF tropomyosin were distinct from chicken skeletal and cardiac tropomyosins on two-dimensional gels. The mixture of CEF tropomyosin has been isolated by the combination of Triton/glycerol extraction of monolayer cells, heat treatment, and ammonium sulfate fractionation. The yield of tropomyosin was estimated to be 1.4% of total CEF proteins. The identical set of tropomyosin isoforms could be found in the antitropomyosin immunoprecipitates after the cell-free translation products of total poly(A)+ RNAs isolated from CEF cells. This suggested that at least seven mRNAs coding for these tropomyosin isoforms existed in the cell. Purified tropomyosins (particularly 1, 2, and 3) showed different actin-binding abilities in the presence of 100 mM KCl and no divalent cation. Under this condition, the binding of tropomyosin 3 (3a + 3b) to actin filaments was significantly weaker than that of tropomyosin 1 or 2. CEF tropomyosin 1, and probably 3, could be cross-linked to form homodimers by treatment with 5,5'-dithiobis-(2-nitrobenzoate), whereas tropomyosin a and c formed a heterodimer. These dimer species may reflect the in vivo assembly of tropomyosin isoforms, since dimer formation occurred not only with purified tropomyosin but also with microfilament-associated tropomyosin. The expression of these tropomyosin isoforms in Rous sarcoma virus-transformed CEF cells has also been investigated. In agreement with the previous report by Hendricks and Weintraub (Proc. Natl. Acad. Sci. USA., 78:5633-5637), we found that major tropomyosin 1 was greatly reduced in transformed cells. We have also found that the relative amounts of tropomyosin 3a and 3b were increased in both the total cell lysate and the microfilament fraction of transformed cells. Because of the different actin-binding properties observed for CEF tropomyosins, changes in the expression of these isoforms may, in part, be responsible for the reduction of actin cables and the alteration of cell shape found in transformed cells.