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At least 127 records · Page 7Linked to original sources
PubMed1984

Molecular analysis of the period locus in Drosophila melanogaster and identification of a transcript involved in biological rhythms.

We have isolated and analyzed DNA sequences encompassing the period (per) locus of Drosophila melanogaster. The location of this clock gene was delimited by the molecular mapping of chromosome aberrations at or very near the per locus. At least five RNAs are transcribed from this region. One of these transcripts, a 0.9 kb species, is strongly implicated in per's control of biological rhythms. Two independently isolated arrhythmic mutations at the per locus dramatically reduce the level of this transcript. Furthermore, the level of the 0.9 kb transcript is strongly modulated during a light/dark cycle. We discuss evidence, from previously reported genetic and phenotypic analysis of per's function, suggesting that this region may be complex and that several gene products from the per region, including this 0.9 kb transcript, may be involved in the different aspects of normal rhythmicity influenced by this clock gene.

Animals↗
PubMed1984

Gene mapping within the T/t complex of the mouse. III: t-Lethal genes are arranged in three clusters on chromosome 17.

Lethal t mutations belonging to seven different complementation groups have been mapped. The overall picture emerges as three clusters of t-lethal genes: one near the proximally located tail interaction factor (tT) containing tw73; one numerous cluster associated with the MHC and including tw32, t12, tw5, tw18, and tLub-1; and one distal cluster close to the locus of tf encompassing, t0, t6, and tw12. In the two cases examined, members of the same complementation group map to the same location. Evidence is presented that more than one mutant site may be necessary for the lethality of some lethal t "mutations," and that the expression of a specific lethal phenotype may depend on cis-interactions between multiple mutations.

Alleles↗
PubMed1985

Developmentally controlled and tissue-specific expression of unrearranged VH gene segments.

It is generally accepted that unrearranged immunoglobulin VH gene segments are not expressed and that assembly of a complete heavy chain gene is required to activate a previously silent VH promoter. We report that unrearranged VH gene segments are indeed expressed at a high level, but only in a developmentally controlled and tissue-specific manner. Unrearranged VH expression is limited to the very early stages of the B-lymphocyte differentiation pathway, and it is most prominent in cells undergoing VH to DJH rearrangement. Germ-line VH expression is independent of the heavy chain enhancer, may be controlled by 5' sequence elements, and is repressible by LPS. In contrast to earlier interpretations, our results demonstrate that the lack of unrearranged VH segment expression in mature, Ig-secreting cells is due to the inactivation of a previously active locus. These findings may provide insight into the mechanisms that control ordered rearrangement and allelic exclusion.

Animals↗
PubMed1992

Molecular evaluation of residual disease as a predictor of relapse in acute promyelocytic leukaemia.

Acute promyelocytic leukaemia (APL) is characterised by a unique fusion transcript, PML/RAR alpha. We tested for this transcript in 35 APL patients who were in apparent remission after various treatments. 11 of 13 patients who tested positive 4 months after achieving remission were in relapse 1-4 months later. All 22 patients who tested negative at 4 months were disease-free after a further 3 months to five years. The test may therefore prove useful in determining the need for additional treatment during clinical remission.

Carrier Proteins↗
PubMed1996

Relapse of acute promyelocytic leukemia follows serial negative RT-PCR assays: a cautionary tale.

Six patients with acute promyelocytic leukaemia (APL) and t(15;17) were investigated by cytogenetics and by reverse transcriptase polymerase chain reaction (RT-PCR) for the fusion transcript PML-RARA. The clone was detected in remission following all-trans retinoic acid and chemotherapy by cytogenetics and/or by RT-PCR up to 2 months from diagnosis. Thereafter the PML-RARA transcript was not seen in 20/21 first remission samples in five cases studied. Remission was maintained in two patients, one following bone marrow transplantation (BMT). Despite serial negative RT-PCR results, PML-RARA reemerged at or prior to relapse following BMT in the remaining three cases. Frequent molecular monitoring and caution in the interpretation of negative RT-PCR results are indicated in APL.

Adolescent↗
PubMed1983

Absence of cis-acting transposition immunity with Tn7.

It is possible in two steps to insert into the plasmid RP4 two copies of the transposon Tn7. This was demonstrated using a wild-type Tn7 in the first step, and a Tn7 derivative (carrying an additional marker), in the second step. The two successive transpositions occurred with the same polarity and frequency. The genetic structures of the resulting plasmids, predicted from the phenotypes of the bacterial host, were confirmed by direct analysis of the plasmid DNAs. Thus, the phenomenon of cis-acting transposition immunity, described with Tn1 or Tn3, does not take place in the case of Tn7.

Cloning, Molecular↗
PubMed1988

Robertsonian chromosome recombinants are rare in cancer.

Whole-arm Robertsonian rearrangements are common constitutional changes of chromosomes that possess unusual properties. They occur spontaneously, are not inducible by ionizing radiation or clastogenic chemicals, show an exceptionally high meiotic mutation rate and nonrandom chromosome composition. A sample of 30 Robertsonian rearrangements in cancer patients revealed only three to have been acquired, none as a primary or significant secondary cancer chromosome change. The frequency of Robertsonian rearrangements is in the range of one per 1,100 at birth versus one acquired per 10,000 in cancer. Consistent with the prediction that Robertsonian rearrangements are recombinants, a subfamily of alpha satellite DNA displays selective homology between the centromeric regions of acrocentric autosomes proportional to their preferential entry into Robertsonian chromosomes. Recombination leading to Robertsonian rearrangements is common in meiosis, but is rare in mitosis. Hence, Robertsonian rearrangements are rare in cancer.

DNA, Satellite↗
PubMed1977

Construction and characterization of new cloning vehicles. I. Ampicillin-resistant derivatives of the plasmid pMB9.

In vitro recombination via restriction endonucleases and the in vivo genetic translocation of the Ap resistance (Apr) gene resulted in the construction of a new cloning vehicle, the plasmid pBR313. This vector was derived from a ColE1-like plasmid and, while it does not produce colicon E1, it still retains colicin E1 immunity. The Apr and tetracycline resistance (Tcr) markers carried in pBR313 were derived from the ampicillin transposon (TnA) of pRSF2124 and pSC101 respectively. During the construction of pBR313, the TnA component was altered and the Apr gene in pBR313 can no longer be translocated. This plasmid has a molecular weight of 5.8 Mdalton and has been characterized using thirteen restriction enzymes, six of which (EcoRI, SmaI, HpaI, HindIII, BamHI and SalI) cleave the plasmid at unique restriction sites. This allows the molecular cloning of DNA fragments generated by these six enzymes. The restriction sites for the latter three enzymes, HindIII, BamHI and SalI, are located in the Tcr gene(s). Cloning DNA fragments into these sites alters the expression of the Tcr mechanisms thus providing a selection for cells carrying recombinant plasmid molecules. An enrichment method for AprTcS cells carrying recombinant plasmid molecules is described.

Ampicillin↗
PubMed1992

Transcriptional regulation by the nuclear receptor superfamily.

In the past year, additional experimental data have expanded our understanding of the molecular mechanisms that underlie nuclear receptor control of regulatory programs. It is increasingly clear that steroid members (e.g. glucocorticoid and estrogen) and non-steroid members (e.g. retinoic acid, thyroid hormone, and vitamin D) of the nuclear receptor superfamily may utilize distinct strategies in achieving their complex control of gene regulation.

Animals↗