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M Piechaczyk

Publications and source records attributed to M Piechaczyk.

At least 91 records · Page 5Linked to original sources
PubMed1986

Transcriptional and post-transcriptional regulation of c-myc expression during the differentiation of murine erythroleukemia Friend cells.

c-myc RNA rapidly decreases to barely detectable levels in Friend erythroleukemia cells induced to differentiate upon the addition of dimethylsulfoxide. We show here that c-myc gene is down-regulated both at the transcriptional level presumably by a block in the elongation of primary transcripts and at the post-transcriptional level by an increase in the degradation of its mRNA.

Animals↗
PubMed1985

Aberrant c-myc RNAs of Burkitt's lymphoma cells have longer half-lives.

BL67 and BL18 are Burkitt's lymphoma cell lines with t(8;14) translocations (the breakpoint is in the first exon and first intron, respectively) in which the mu-heavy chain switch region is fused to the c-myc gene in head to head orientation. In both cell lines only aberrant c-myc RNAs are found. BL67 cells contain two c-myc RNA species of 2.4 and 3.5 kb. The 2.4-kb RNA is initiated at several cryptic promoters in the first intron. The 3.5-kb RNA is transcribed from the immunoglobulin heavy chain anti-sense strand across the breakpoint of the translocation into the first exon of the c-myc gene and is then normally spliced using the physiological splice donor and acceptor sites of the c-myc gene. BL18 contains c-myc RNA of 2.4 kb initiated at cryptic promoters in the first intron and additional RNAs of 0.90 kb and 0.74 kb transcribed from the dual c-myc promoters on the reciprocal fragment of the translocation. The cytoplasmic turnover of these RNAs differs significantly from that of the normal c-myc message. The 3.5-kb RNA of BL67 cells and the 0.90-kb and 0.74-kb RNAs of BL18 cells, which are both hybrid molecules consisting of c-myc and immunoglobulin sequences, have a half-life of several hours in contrast to the normal c-myc message with a half-life of 15 min. The aberrant 2.4-kb c-myc RNAs of BL67 and BL18 cells are also more stable than the normal c-myc message and disappear with a half-life of 50 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Burkitt Lymphoma↗
PubMed1985

Chromatin structure of the murine c-myc locus: implications for the regulation of normal and chromosomally translocated genes.

To assess possible alterations of c-myc transcriptional control in murine B-cell tumors, we have investigated the pattern of DNaseI hypersensitive sites in the gene's putative regulatory region and within the gene in a variety of genomic contexts. A number of such sites were found in several cell types, but none of these was detectable in a gene which was shown to be transcriptionally silent by the criterion of elongation of nascent transcripts in isolated nuclei. These results differ from those of a previous study, in which a DNaseI-hypersensitive site approximately 2 kb upstream of the gene was proposed to be associated with negative regulation of c-myc transcription in human cells. An analysis of DNA sequences presented here reveals that this region is highly homologous between mouse and human, suggesting that these upstream hypersensitive sites do not reflect species-specific regulatory elements. We also present data indicating that this hypersensitive site distinguishes the c-myc alleles in translocation-positive plasma cell tumors which lack c-myc rearrangement. Furthermore, we report the existence of hypersensitive sites within the gene. One of these appears to be associated with cryptic promoters that are employed only when the normal promoters are lost as a consequence of chromosome translocation. These results are discussed in the context of c-myc translocation and gene breakage and with respect to possible stage-specific regulation of the gene's transcriptional competence.

Animals↗
PubMed1985

Comparative study of the L1 family in the genus Mus. Possible role of retroposition and conversion events in its concerted evolution.

The long interspersed repetitive family L1 was analysed in different species belonging to the genus Mus. It is shown to be highly conserved even in M.n. setulosus, which diverged from the other species around ten million years ago. The study of the linkage between diagnostic restriction sites in the various species and the sequence variations of different regions of the L1Md repeat shows that the L1 family undergoes concerted changes involving subsets of repeats. The rate at which this homogenization process occurs does not appear to be the same for all the subfamilies detected. The L1Md repeat in the twelfth intron of the serum albumin gene of Balb/c mice is shown to be a recent insertion. The role retroposon- and gene conversion-like events may play in the concerted evolution of the L1 family is discussed.

Animals↗
PubMed1985

Various rat adult tissues express only one major mRNA species from the glyceraldehyde-3-phosphate-dehydrogenase multigenic family.

We have isolated and sequenced a full-length cDNA clone encoding rat glyceraldehyde-3-phosphate-dehydrogenase (GAPDH, E.C.1.2.1.12). The entire mRNA is 1269 nucleotides long exclusive of poly(A) and contains respectively 71 and 196 bases of 5' and 3' non-coding regions. Primer extension as well as S1 nuclease protection experiments clearly established that a single (or at least a highly prominent) GAPDH mRNA species is expressed in all rat tissues examined. This sequence allowed the determination of the hitherto unknown primary structure of rat GAPDH which is 333 aminoacids long. Comparison between GAPDH sequences from rat, man and chicken revealed a high degree of sequence conservation at both nucleotide and protein levels.

Amino Acid Sequence↗
PubMed1985

Posttranscriptional mechanisms are responsible for accumulation of truncated c-myc RNAs in murine plasma cell tumors.

c-myc Messenger RNAs are known to be extremely unstable (t1/2 = 10 min) in normal and tumor cells, suggesting that degradation could play an important role in regulating their steady state level in the cytoplasm. We have investigated the stabilities of c-myc mRNAs in three murine plasmacytomas, where the c-myc gene either remains intact (ABPC20) or exists in a truncated form (MPC-11 and J558L) subsequent to 6;15 or 12;15 chromosome translocations respectively, and in an A-MuLV-induced pre-B lymphoma line (18-81.5) that lacks chromosome translocations and contains both c-myc genes in their normal context. The truncated myc genes in J558L and MPC-11 lack the promoters of the normal gene but are transcribed from cryptic promoters within the first c-myc intron. We found that posttranscriptional processes are largely responsible for the higher steady state accumulations of truncated c-myc transcripts, while broken and intact c-myc genes are transcribed at comparable rates.

Animals↗
PubMed1985

Increased rate of degradation of c-myc mRNA in interferon-treated Daudi cells.

The recent observation made in our laboratory that cellular myc (c-myc) mRNA has a very short half-life in a variety of normal and transformed human cells emphasized the potential importance of post-transcriptional regulation of c-myc gene expression. Jonak and Knight [Jonak, G. J. & Knight, E., Jr. (1984) Proc. Natl. Acad. Sci. USA 81, 1747-1750] have reported a selective reduction of c-myc mRNA accumulation in lymphoblastoid Daudi cells treated with human beta interferon. This provided a suitable situation in which to examine a possible action of negative modulators of c-myc expression at the level of mRNA stability. Our results confirm the observation by Jonak and Knight that c-myc mRNA level is depressed in cells treated with beta interferon and extend it to alpha 2 interferon. Furthermore, we now demonstrate that interferon has no effect on c-myc transcription rate in isolated nuclei but rather reduces the half-life of its mRNA. Conversely, we show that it increases the level of HLA-A2 mRNA by stimulating its transcription.

Gene Expression Regulation↗
PubMed1985

Production and characterization of monoclonal antibodies against human thyroglobulin.

Spleen cells of Biozzi-HR mice immunized with human thyroglobulin (hTg) were fused with P3-X63-Ag8.653 mouse myeloma cells. Twenty monoclonal antibodies (MAbs) selected by an enzyme immunoassay (indirect ELISA) were produced, purified and characterized. The equilibrium association constant (Ka) of one of the MAbs, determined by Scatchard analysis of the ELISA data, was found to be 2 X 10(9) M-1; the Ka of the other MAb, estimated from titration curves by comparison with the aforementioned MAb, ranged from 8 X 10(9) M-1 to 6 X 10(7) M-1. The reaction between the MAb and hTg was not inhibited by thyroxin (T4), triiodothyronine (T3) and triiodothyropropionic acid (DT3). Species specificity of the MAb was studied using bovine and porcine Tgb. The topology of the MAb was investigated by competitive inhibition immunoassays. Seven distinct antigenic regions were identified.

Antibodies, Monoclonal↗
PubMed1984

Characterization of the transcription products of glyceraldehyde 3-phosphate-dehydrogenase gene in HeLa cells.

We have partially purified the messenger RNA coding for glyceraldehyde-3-phosphate dehydrogenase (GAPDH, EC 1.2.1.12) from HeLa cells and obtained a cDNA clone containing part of its sequence. Using this clone to probe electrophoregrams of RNA transferred to nitrocellulose, we have investigated the characteristics of nuclear and cytoplasmic transcripts in these cells. In the cytoplasm, nature GAPDH mRNA was detected in Northern blots as an intense band, apparently unique, of approximately 1400 nucleotides. The half-life of this mRNA was determined both from the decay kinetics, after a chase with actinomycin D, and from the labeling kinetics during an accumulation experiment. Both kinds of experiments yielded a half-life value of about 8 h, while the accumulation experiment indicated that steady-state GAPDH mRNA amounted to about 1.6% of cytoplasmic poly(A)-rich RNA. Much longer species, likely to be restricted to the nucleus, were also detected in RNA extracted from total cells. At least three discrete species of 1600, 4000, 5800 and 6800 bases were observed above a trailing background extending up to about 8000 bases. This value is commensurate with a functional size of the GAPDH transcription unit in the order of 13000 bases, which we determined by measuring the size of the ultraviolet inactivation target. Until direct evidence can be obtained at the genomic level, the present results provide the first clue to the existence of introns, presumably at least four, in a GAPDH gene from a higher eucaryote.

Amino Acid Sequence↗
PubMed1984

Post-transcriptional regulation of glyceraldehyde-3-phosphate-dehydrogenase gene expression in rat tissues.

We have isolated and identified cDNA clones containing part of the coding sequence for rat glyceraldehyde-3-phosphate-dehydrogenase (GAPDH, E.C. 1.2.1.12). By using one of these clones as a probe, we have shown that: i) the abundance of GAPDH mRNA is different in various tissues of the adult rat and in good correlation with the abundance of the enzyme; ii) the transcription rates are quite similar in all tissues tested. We therefore conclude that the tissue-specific differential GAPDH gene expression is regulated by adjusting the abundance of its mRNA at the post-transcriptional level.

Animals↗
PubMed1984

Complete nucleotide sequence of the messenger RNA coding for chicken muscle glyceraldehyde-3-phosphate dehydrogenase.

The complete nucleotide sequence for chicken glyceraldehyde-3-phosphate dehydrogenase mRNA has been determined, thereby extending the longest such sequence previously reported (Dugaiczyk et al. Biochemistry, 1983, 22, 1605-1613) by 27 nucleotides. The complete mRNA with the exclusion of poly(A) is 1284 nucleotides long and contains 56 nucleotides of 5' non coding sequence and 229 nucleotides of 3' non coding region. Knowledge of the complete sequence allows us to propose secondary structures models which may be of biological significance.

Animals↗
PubMed1984

Extreme instability of myc mRNA in normal and transformed human cells.

To address the possibility that the expression of the myc gene might be regulated at a post-transcriptional level, we have investigated the half-life of myc mRNA in various cells. Our survey included normal human embryonic fibroblasts as well as transformed human cells of various origins: cervix carcinoma (HeLa), breast carcinoma (MCF7), Burkitt lymphoma (Daudi), and promyelocytic leukemia (HL60). All these cells revealed an extreme instability of myc mRNA (half-life, approximately equal to 10 min), suggesting that the control of myc mRNA degradation might be a general means (although not necessarily exclusive) of regulating both the level and the timing of myc gene expression. Inhibition of protein synthesis resulted in a dramatic stabilization of myc mRNA in HeLa, MCF7, and HL60 cells, suggesting that the controlling element might itself be, at least in these cells, a protein of rapid turnover. This finding opens the way to studying the mechanism of myc mRNA inactivation in these different cell types. However, protein synthesis inhibition had no effect on myc mRNA instability in other transformed (Daudi) cell lines as well as normal embryonic human fibroblasts. These different types of behavior suggest that the post-transcriptional control of myc gene expression might involve multiple factors that would be differently affected in various cell types.

Cell Transformation, Neoplastic↗
PubMed1983

Insertion sequences and tandem repetitions as sources of variation in a dispersed repeat family.

Sequencing of ten clones from the major dispersed repeat family of mouse (MIF-1) has identified two novel types of sequence variation. Two clones contain small insertion sequences that are flanked by five base-pair duplications of the target site. A third clone, MIFC70, contains a 20 base-pair insertion composed of four direct repeats of a five base-pair sequence. This insertion may have arisen by successive out-of-register pairing and cross-over events at an ancestral target sequence. MIFC70 is also distinguished by its divergence from the standard MIF-1 sequence; whereas for standard clones of the MIF-1 family inter-copy divergence does not exceed 10%, the divergence between MIFC70 and standard clones is of the order of 26%. MIFC70 may represent an aberrant copy which is now isolated from the bulk of the repeat family and is free to diverge.

Animals↗
PubMed1982

Mouse DNA sequences complementary to small nuclear RNA U1.

A mouse genomic library was screened for sequences complementary to U1 nuclear RNA. Out of the eight clones tested, none contained more than one copy of U1. Six of them were identical and one of those (clone 0U1-XIII) was further analyzed. This latter clone contained no other gene for discrete species of small size RNA in the 8 Kb EcoRI fragment encoding U1. A 248 bp Bg1II fragment from 0U1-XIII encompassing the full length of U1 as well as flanking regions on both sides has been subcloned and sequenced in M13 phage. Although the coding region was 96.5% homologous to rat U1a RNA, there is no direct evidence that this clone is a true gene. 3' and 5' flanking sequences of this as well as other published clones have been searched for homologies and the results of this search are discussed.

Animals↗