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J Harel

Publications and source records attributed to J Harel.

At least 109 records · Page 6Linked to original sources
PubMed1984

Alpha actin gene exist in an active structural configuration in the proliferating myoblasts as well as in differentiated myotubes of the L6 line.

Single-stranded DNA (ssDNA) mainly consisting of transcription sites was probed with cDNA actin clones for studying the expression of actin specific genes during myogenesis in the L6 line of rat myogenic cells. As compared with total nuclear DNA, ssDNA from myoblasts and myotubes was found greatly enriched in sequences complementary to both muscular and non muscular actin sequences. In contrast, ssDNA from spleen, hepatocytes or hepatoma cells was found enriched only in sequences complementary to non muscle actin cDNA. Actin specific sequences accumulated in the ssDNA fraction are almost entirely derived from the coding DNA strand. The DNAase I sensitivity of the actin genes sequences in myogenic and non myogenic cells correlated the data obtained with the ssDNA fraction. It is concluded that the muscle specific actin genes is either transcriptionally active or at least exist in an active configuration in the proliferating myoblasts as well as in the terminally differentiated myotubes.

Actins↗
PubMed1984

Changes in gene expression following neoplastic transformation of rat myogenic cells.

Two malignant sublines, M4 and RMS4 , were previously derived from the recloned L6 line of rat myogenic cells. Comparative studies in tissue culture and inoculation into suckling rats indicated that M4 cells and RMS4 cells may be considered as low-malignant and high-malignant cells, respectively, while L6 cells are not malignant. In the present work, we used extracts from L6 cells, M4 cells, and RMS4 cells collected during the period of exponential growth, to compare their polyadenylic acid-containing messenger RNA (mRNA) populations and the corresponding cell-free translation products. Analysis of the hybridization kinetics between radioactive complementary DNA and homologous or heterologous cellular RNAs indicated that L6 cells contained about 28,000 distinct polyadenylic acid-containing mRNA sequences of 1.8 kilobases each, of which 2,000 to 2,500 and 4,000 to 5,000 were missing (or at least were very infrequent) in M4 cells and RMS4 cells, respectively. Using a minor fraction of the RMS4 cell complementary DNAs, partially purified through repeated complementary DNA-RNA hybridization cycles, it was further shown that RMS4 cells contained at least 700 to 800 distinct mRNA species, mainly belonging to the class of low abundance, which appeared to be absent in L6 cells. Most of these mRNA species were also found with a lower frequency in M4 cells. Bidimensional analysis of the cell-free translation products directed by polyadenylic acid-containing mRNA revealed some remarkable differences, in particular the synthesis in a RMS4 cell extract of at least three major polypeptides, possibly related either to the neoplastic process itself or to the stage of malignant transformation.

Animals↗
PubMed1983

A destabilized DNA conformation associated with tightly bound nuclear proteins in active genes of rat myoblast.

Purified nuclei from tissue cultured myoblasts were disrupted and centrifuged to equilibrium in a sarcosyl-caesium chloride gradient. A small portion (1.3% - 1.9%) of the non histone proteins (NHP) were banded with DNA in a high density region of the gradient. The DNA tightly bound to proteins representing about 0.6% of the total nuclear DNA was degraded after treating cell nuclei with S1 nuclease or DNAse I but resisted to mild micrococcal nuclease digestion. A large portion of the DNA sequences complementary to homologous RNA was concentrated in this DNA-proteins fraction. These finding suggest that a subset of NHP strongly associated to the active DNA regions play a role in the destabilisation of the double helical DNA during transcriptional processes.

Animals↗
PubMed1983

Common multigenic activation in different human neoplasias.

It was previously shown that a common multigenic component, designated as tumor-specific DNA (tsDNA), was transcriptionally active in human lymphoid neoplasias and only slightly active, if at all, in normal lymphoid cells, including the Priess cell line immortalized by Epstein-Barr virus. In the Burkitt lymphoma-derived Raji cell line, tsDNA corresponded to 2500-3000 distinct transcription units, arbitrarily defined as encoding mRNA chains of 1000 kds each. In the present study, radioactive Raji cell tsDNA was isolated by a recycling procedure which eliminates transcribed DNA sequences common to both the Raji cell and the Priess cell, and was used as a probe for homologous transcripts. The major part of this probe could be hybridized to RNAs from all the human neoplasias studied: cultured cell lines derived from leukemias, malignant lymphomas or sarcomas, leukemic cells or solid tumors (sarcomas and carcinomas) recovered from patients. In contrast, only a minor portion of Raji cell tsDNA could be hybridized to RNAs from non-malignant cells, normal human lymphoid cells or fibroblasts grown in culture, fetal and chorioplacental tissues. It is concluded that a common multigenic set is activated in a wide variety of, and perhaps in all, human neoplasias.

Burkitt Lymphoma↗
PubMed1982

The small chromatin fragments released by micrococcal nuclease from hepatoma tissue cultured cell nuclei are strongly enriched in coding DNA sequences and are related to an actively transcribed single-stranded DNA fraction.

It was shown with the use of specific probes that mild micrococcal nuclease digestion released from chromatin actively-transcribed genes as small nucleosome oligomers. In the present work we demonstrate that most if not all of the active genes are accessible to the nuclease. It was found that the short released fragments are greatly enriched in transcribed DNA sequences, the most enriched being the dimers of nucleosomes since 35% of their DNA could be hybridized to cytoplasmic RNA. The results of cDNA-DNA hybridizations indicate that the monomers and dimers of nucleosomes contain most of the DNA sequences which encode poly(A+) RNAs, however larger released fragments include some transcribed sequences, while the nuclease resistant chromatin is considerably impoverished in coding sites. These evidences are the finding that about 25% of the DNA from the dimers of nucleosomes are exclusively located in this class of fragments, tend to prove that the active chromatin regions are attacked in a non-random way by micrococcal nuclease. We have previously isolated, without using exogenous nuclease, an actively transcribed genomic fraction amounting to 1.5-2% of the total nuclear DNA, formed of single-stranded DNA. In the present study we show that all or nearly all the single-stranded DNA sequences could be reassociated with the DNA fragments present in the released monomers and dimers of nucleosomes. Our observations confirmed our previous finding that the greatest part of single-stranded DNA selectively originates from the coding strand of genomic DNA.

Animals↗
PubMed1982

Isolation of a mouse DNA fraction which encodes more informational than non informational RNA sequences.

A small fraction of single-stranded DNA (ssDNA), amounting to 1.5--2% of the total DNA, was isolated from native nuclear DNA of mouse Ascites tumour cells. In RNA-driven annealing reactions, 40--42% of the ssDNA, (labelled with [3H]-thymidine or 125I) could be hybridized to cytoplasmic RNA was compared with 4--4.5% for the non repetitious component of bulk DNA and 60--63% of the ssDNA could be hybridized to nuclear RNA as compared with 20--22% for bulk DNA. It was also found that most of the ssDNA sequences which are hybridizable to homologous RNA, consisted of non self-reassociating DNA regions (which can be reassociated with non repetitious bulk DNA). These findings complete earlier data obtained in other cell systems and demonstrate that ssDNA mainly originates from active DNA transcription sites which encode informational RNA sequences. It is proposed that ssDNA is formed via selective endogenous nuclease attacks presumably at an early stage of the DNA purification procedure.

Animals↗
PubMed1982

Effect of sodium butyrate on messenger RNA populations in myogenic cells in culture.

Sodium butyrate, when added in millimolar concentrations to a culture of myoblasts of the L6 cell line, inhibits reversibly cell proliferation and differentiation. The aim of this work was to study the effect of sodium butyrate on the nuclear and cytoplasmic RNAs in these cells. We have prepared (3H) DNAs complementary to cytoplasmic polyadenylated RNAs from treated and untreated cells and performed homologous and heterologous hybridizations with cytoplasmic polyadenylated RNAs and with total nuclear RNAs. The hybridization kinetics led to the following conclusions: a) Hybridization with nuclear RNAs shows that butyrate allows the transcription of most of the RNA sequences synthesized in proliferating myoblasts, including the sequences that are no longer synthesized in untreated myotubes. However some differences in the hybridization saturation levels indicate that sodium butyrate might modify the expression of a limited number of genes involved in cell proliferation, muscular differentiation, or both. b) Hybridization with cytoplasmic polyadenylated RNAs shows that sodium butyrate acts also at a post-transcriptional level, it produces a large decrease in the frequency of the abundant sequences present in untreated cells, but has little effect on the total number of different RNA species.

Animals↗
PubMed1982

Abundant messenger RNA sequences common to transplanted mouse tumours of different tissue origins.

Radioactive cDNA, cell-free-synthesised on poly(A)-rich mRNAs from mouse FLS-ascites tumour cells, were separated into two fractions corresponding to abundant mRNA species and to rare mRNA species respectively, the former being nearly 100-times more abundant per cell than the latter. Aliquots of each fraction were hybridized to a large excess of RNA of different origins; three ascites tumours (the FLS, Krebs 2 and Ehrlich tumours) all transplanted in animals; one established line of Friend erythroleukemia cells serially passaged in culture; adult organs and whole mouse embryos. It was shown that all or nearly all the mRNA species, in particular the abundant ones, were present and similarly distributed in the three transplanted tumour strains studied, despite their different tissue origins. The great majority of abundant mRNA species were also present in Friend erythroleukemia cells but about two-times less frequent relative to transplanted tumours. Much greater differences were found as compared with non-malignant cells. In particular, although the majority of the abundant mRNA species were also found in all normal tissues studied, they were on the average 7-8-times less abundant in adult liver or in 10-days-old embryos, and 10-times less abundant in adult brain, than in tumour cells. Finally about 10% of the abundant RNA species common to all transplanted tumours appeared to be absent in normal cells, whatever their growth rates or stage of differentiation. The possible implications of these findings are discussed.

Animals↗
PubMed1982

[2 malignant cell lines derived from strain L6 of rat myogenic cells].

A nonfusing variant M4 of the L6 line of rat myoblasts was isolated. This subline was tumorigenic when inoculated into suckling rats. Comparative studies of cells growth in vitro, serum requirement, cell adhesiveness and capacity to form colonies in soft agar confirmed that M4 cells had undergone neoplastic transformation while L6 cells exhibited normal characteristics. Another subline designated as RMS4 was derivated from M4 cells tumors. Growth characteristics in vitro and karyotype analysis indicated that RMS4 cells presented a higher degree of transformation as compared with M4 cells. Both M4 and RMS4 cell cultures seem to produce a C-type virus.

Animals↗
PubMed1981

Manifold expression of new cellular genes in human lymphoid neoplasia.

Previous studies performed in our laboratory have shown that a minor single-stranded DNA component (ssDNA) isolated from the bulk of double-stranded nuclear DNA (nDNA) of human, murine, or avian cells consisted mainly of active transcription sites. In the present work, ssDNA isolated from human lymphoid cells, either malignant or not, amounted to 1.2-1.4% of the total nDNA. This was labeled with 125I and utilized as a probe in RNA-driven iterative hybridization and cross-hybridization assays. In all cases of neoplasia studied, the same subfraction of ssDNA (equivalent to 10-12% of the total ssDNA) from malignant cells could be hybridized with cytoplasmic RNA from malignant cells, whatever their origin: acute lymphoid leukemia cells collected from blood of leukemic patients, local lymphosarcomas, or cells from two established strains grown in suspension, one Epstein-Barr virus positive (Raji strain), the other Epstein--Barr virus negative (Ramos strain). The majority of these tumor-specific DNA sequences could be reassociated with unique-copy DNA from both normal and malignant cells and were not expressed in normal lymphoid cells, including those of an established strain immortalized by Epstein--Barr virus and multiplied in culture. It is concluded that a great number of new transcription units, in the range of 2500-3000 per cell genome, were activated after spontaneous malignant transformation of lymphoid cells.

Base Sequence↗
PubMed1980

The use of the Denver Developmental Screening Test in infant welfare clinics.

The results of a single Denver Developmental Screening Test performed at the age of nine months on 823 infants attending maternal and child health centres were compared with the developmental information recorded by public health nurses during their routine well-baby care of these same infants. The single Denver test detected a significantly greater number of infants with developmental delay than did the routine observations, and the nurses tended to under-use the available resources for developmental assessment. Suggestions are made for more effective use of maternal and child health centres in the primary recognition of developmental delay.

Child Development↗
PubMed1979

Relationship between single-stranded DNA isolated from mouse cells transformed by simian virus 40 and transcription of cellular and virus genes.

A minor fraction of single-stranded DNA (ssDNA) was isolated by an improved method of hydroxylapatite chromatography (HAC) from the native nuclear DNA (nDNA) of SV--3T3 cells, non-productively transformed by SV40. Molecular hybridization, monitored by the use of S1 nuclease, HAC, isopycnic centrifugation and thermal melting showed that ssDNA from SV-3T3 cells (which amounts to 1.5 to 2% of the total nDNA) has the same characteristics as ssDNA previously isolated from other cell species. Only 27 to 28% of ssDNA can be self-hybridized but the greatest part can be reassociated to the non-repetitive portion of nDNA and up to 38% hybridized to homologous RNAs, as compared with 7 to 8% for bulk nDNA. Highly radioactive virus probes (SV40-3H-cRNA synthesized in a cell-free system and the separated 'early' and 'late' strands of SV40 DNA labelled with 125I) were annealed to different excess amounts of cellular DNA. Both the quantities of each probe hybridized at saturation levels and the various reaction kinetics indicated that ssDNA is greatly enriched for virus sequences, mainly originating from the 'early' DNA strand which is predominantly expressed in SV-3T3 cells. The mode of formation of ssDNA is discussed in the light of other findings on the effects of DNA untwisting proteins and susceptibility of active animal genes to selective enzymic attacks.

Animals↗