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Biomedical subjects

W D Park

Publications and source records attributed to W D Park.

At least 37 records · Page 2Linked to original sources
PubMed1985

Regulation of potato tuber protein accumulation by gibberellic Acid.

Many studies have shown that gibberellic acid (GA(3)) inhibits tuberization in potato (Solanum tuberosum L.). In this study, we have utilized the 40 kilodalton glycoprotein, patatin, as a marker for biochemical events associated with the process of tuberization. To determine the effects of exogenous applications of GA(3) on the induction of the accumulation of this major tuber protein, we measured patatin levels in tubers from treated whole plants, petioles from a single-node cutting system with GA(3) applied in a lanolin paste, and stolon tips cultured in vitro on an inductive medium supplemented with GA(3). In all three systems, GA(3) inhibited the accumulation of patatin and the major 15 and 22 kilodalton tuber proteins. This effect appeared to be selective since most of the other proteins were not affected and, in tubers, at least one protein was stimulated by GA(3). These results suggest that GA(3) can reverse biochemical events of tuberization in tubers as well as prevent the accumulation of the major tuber proteins in other inducible tissues.

Journal Article↗
PubMed1984

Isolation and sequence analysis of cDNAs for the major potato tuber protein, patatin.

A cDNA library from membrane-bound poly(A)+ mRNA of developing potato tubers was constructed and two classes of essentially full-length cDNA clones for a precursor to the major tuber glycoprotein, patatin were isolated. Sequence analysis shows that the two classes are approximately 99% homologous and correspond to the two major species of patatin identified previously by NH2-terminal amino acid sequence analysis. Sequence analysis also predicts that patatin is synthesized with a 23 amino acid signal sequence. Northern blot analysis shows that patatin mRNAs are 1550 +/- 50 nucleotides in length and are normally not present in polyribosomal or total RNA from stems or leaves.

Amino Acid Sequence↗
PubMed1984

Endosperm Protein Synthesis and l-[S]Methionine Incorporation in Maize Kernels Cultured In Vitro.

This study was conducted to examine protein synthesis and l-[(35)S] methionine incorporation into the endosperm of Zea mays L. kernels developing in vitro. Two-day-old kernels of the inbred line W64A were placed in culture on a defined medium containing 10 microCuries l-[(35)S] methionine per milliliter (13 milliCuries per millimole) and harvested at 10, 15, 20, 25, 30, 35, and 40 days after pollination. Cultured kernels attained a final endosperm mass of 120 milligrams compared to 175 milligrams for field-grown controls. Field and cultured kernels had similar concentrations (microgram per milligram endospern) for total protein, albumin plus globulin, zein, and glutelin fractions at most kernel ages.Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing patterns for endosperm proteins were similar for field and cultured kernels throughout development. By 15 days, over 70% of the l-[(35)S]methionine taken up was present in endosperm proteins. Label incorporation visualized by fluorography generally followed the protein intensity of the stained gels. The high methionine content, low molecular weight zeins (i.e. 15 and 9 kilodaltons) were highly labeled. All of the radioactivity in hydrolyzed zein samples was recovered in the methionine peak indicating minimal conversion to l-[(35)S]cysteine. The procedure described here is suitable for long term culture and labeling experiments in which continued kernel development is required.

Journal Article↗
PubMed1983

Analysis of the Heterogeneity of the 40,000 Molecular Weight Tuber Glycoprotein of Potatoes by Immunological Methods and by NH(2)-Terminal Sequence Analysis.

Among the major soluble tuber proteins of potato (Solanum tuberosum L.) is a group of glycoproteins having apparent molecular weights of approximately 40,000. This group of proteins as purified by ion-exchange and affinity chromatography has been given the trivial name ;patatin.' Patatin exists in a number of charge forms which differ between potato cultivars and in some cases can also be resolved into a number of bands by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. However, by immunodiffusion and immunoelectrophoresis, it was found that the isoforms of patatin are immunologically identical both within a cultivar as well as between cultivars. A high degree of homology between the isoforms of patatin is also indicated by NH(2)-terminal amino acid sequence analysis.

Journal Article↗
PubMed1983

Induction and accumulation of major tuber proteins of potato in stems and petioles.

A family of immunologically identical glycoproteins with apparent molecular weights of approximately 40,000 are among the major tuber proteins of potato (Solanum tuberosum L.). These proteins, as purified by ion-exchange and affinity chromatography, have been given the trivial name ;patatin.' To determine if patatin can be used as a biochemical marker to study the process of tuberization, its amount was measured in a variety of tissues by rocket immunoelectrophoresis and by enzyme-linked immunosorbent assay (ELISA).Patatin comprises 40 to 45% of the soluble protein in tubers regardless of whether they are formed on underground stolons or from axillary buds of stem cuttings. Under normal conditions, patatin is present in only trace amounts, if at all, in leaves, stems, or roots of plants which are either actively forming tubers or which have been grown under long days to prevent tuberization. However, if tubers and axillary buds are removed, patatin can accumulate in stems and petioles. This accumulation occurred without any obvious tuber-like swelling and would occur even under long days. In all tissues containing large amounts of patatin, the other tuber proteins were also found as well as large amounts of starch.

Journal Article↗
PubMed1980

Heterogeneity of zein mRNA and protein in maize.

Zein, the prolamine fraction of maize, is localized in the endosperm in membrane-bound structures called protein bodies, which have polyribosomes on their surfaces. These polysomes or the mRNA fraction isolated from them will direct the synthesis of zein-like proteins in vitro. The in vitro products consist primarily of two molecular weight classes but show considerable charge heterogeneity when analyzed by isoelectric focusing. Although the molecular weight classes are very similar for different inbred lines, the isoelectric focusing patterns differ.Results given here suggest that the extensive charge heterogeneity of zein proteins does not result from the presence of a large number of totally distinct mRNAs. Zein proteins synthesized in vitro fall into several families related by sequence homologies in their mRNAs. In Illinois High Protein (IHP) the major zein mRNAs can be classified into three families based on their binding to cloned complimentary DNA copies of IHP zein mRNA. Each of three other lines we have studied (W22, Oh43, and W64A) has zein mRNAs that are related to those of IHP. Among these four lines the molecular weights of the members of a given family are generally similar, but the number of members in a family and their isoelectric points differ.

Journal Article↗
PubMed1977

Non-histone chromosomal proteins: their role in the regulation of histone-gene expression.

Histone-gene expression was studied during the cell cycle of continuously dividing HeLa S3 cells and after stimulation of confluent monolayers of WI-38 human diploid fibroblasts to proliferate. The presence of histone-mRNA sequences was assayed by hybridization to a 3H-labelled single-stranded DNA complementary to histone-mRNA molecules. In HeLa S3 cells histone mRNA sequences were found in the nucleus and associated with polyribosomes during S-phase, but not during G1-phase. Transcripts of S-phase chromatin contained histone-mRNA sequences, but those of G1-phase chromatin did not. Similarly, in WI-38 cells association of histone-mRNA sequences with polyribosomes and transcription of histone-mRNA sequences from chromatin parallel DNA replication. Taken together these results suggest that the regulation of histone-gene expression resides, at least in part, at the transcriptional level. Chromatin-reconstitution studies provide evidence that non-histone chromosomal proteins play a key role in activation of histone-gene transcription during the period of the cell cycle when DNA is replicated. Phosphate groups associated with the S-phase non-histone chromosomal proteins appear to be functionally involved in the control of histone-gene readout.

Animals↗
PubMed1976

Activation of in vitro histone gene transcription from Hela S3 chromatin by S-phase nonhistone chromosomal proteins.

Using a 3H-labeled single-stranded complementary DNA probe for detection of histone mRNA sequences (Thrall, CL., Park, WD., Rashba, HW., Stein, JL.,Mans, RJ., and Stein, GS.(1974), biochem. Biophys. Res. Commun. 61,1443) we have found that histone genes are transcribed in vitro from chromatin isolated from S-phase HeLa cells but not from chromatin isolated from G1-phase cells (Stein, G., Park W., Thrall, C., Mans, R., and Stein, J. (1975a), Nature (London) 2578 764; Stein, G., Park, W., Thrall, C., Mans, R., Steins, J.(1975b), Biochem. Biophys. Res. Commun. 63, 945). Utilizing the technique of chromatin reconstitution, we have recently demonstrated that it is the nonhistone chromosomal protein portion of the genome that is responsible for this difference in in vitro histone gene expression (Stein et al., 1975a). In order to determine whether this is attributable to some component of the S-phase chromosomal proteins that promotes the transcriptin of histone genes, a component of the G1 phase chromosomal proteins that inhibits histone gene transcription, or both, in the present study chromatin from both G1 and S-phase cells was dissociated and then reconstituted in the presence of various chromosomal proteins. The results of this study confirm that it is the nonhistone chromosomal proteins that are responsible for the cell cycle stage specific differences in in vitro histone gene expression and further show that these differences can be accounted for by a component or components of the S-phase nonhistone chromosomal proteins that has the capacity, when reconstituted in the presences of G1 phase chromatin, to render the histone genes transcribable in a dose-dependent fashion.

Cell Division↗
PubMed1976

Synthesis of nuclear proteins during DNA repair synthesis in human diploid fibroblasts damaged with ultraviolet radiation of N-acetoxy-2-acetylaminofluroene.

We have examined the accumulation of newly synthesized nuclear proteins into nuclei during DNA repair synthesis in confluent WI-38 human diploid fibroblasts damaged with ultraviolet radiation or N-acetoxy-2-acetylaminofluroene. In contrast to a marked stimulation of DNA repair synthesis, stimulation of amino acid incorporation into histone polypeptides or into the various molecular weight classes of nonhistone nuclear proteins was not observed. These results suggest that detectable stimulation of newly synthesized nuclear protein incorporation into nuclei does not accompany DNA repair synthesis induced by ultraviolet radiation or a direct acting chemical carcinogen. At least for the special case of repair, DNA synthesis may be uncoupled from histone synthesis.

Acetoxyacetylaminofluorene↗
PubMed1976

Role of nonhistone chromosomal proteins in the regulation of histone gene expression.

Histone gene expression was studied during the cell cycle of continuously dividing HeLa S3-cells and following stimulation of confluent monolayers of WI-38 human diploid fibroblasts to proliferate. The presence of histone messenger RNA (mRNA) sequences was assayed by hybridization to a 3H-labeled single-stranded DNA complementary to histone mRNA's. In HeLa S3-cells, histone mRNA sequences were found in the nucleus and associated with polyribosomes during S phase but not during G1. Transcripts of S-phase chromatin contained histone mRNA sequences but those of G1 chromatin did not. Similarly, in WI-38 cells association of histone mRNA sequences with polyribosomes and transcription of histone mRNA sequences from chromatin parallel DNA replication. Together these results suggest that the regulation of histone gene expression resides, at least in part, at the transcriptional level. Chromatin reconstitution studies provide evidence that nonhistone chromosomal proteins play a key role in activation of histone gene transcription during the period of the cell cycle when DNA is replicated. Phosphate groups associated with the S-phase nonhistone chromosomal proteins appear to be functionally involved in the control of histone gene readout. Although WI-38 human diploid fibroblasts transformed by SV40 exhibit morphological and biochemical modifications characteristic of neoplastic cells, transcription of histone mRNA sequences remains unaltered.

Base Sequence↗