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Biomedical subjects

F Rastinejad

Publications and source records attributed to F Rastinejad.

27 records · Page 2Linked to original sources
PubMed1993

Bacteriophage T7 RNA polymerase. 19F-nuclear magnetic resonance observations at 5-fluorouracil-substituted promoter DNA and RNA transcript.

We have substituted 5-fluorodeoxyuridine (5-FdU) in place of thymidine in defined positions along synthetic bacteriophage T7 promoter DNA sequences. None of the fluoro-substitutions in the promoter DNA sequence reduced transcription yields with T7 RNA polymerase significantly. Substitutions on the coding template strand reduced transcription yields when placed at +3, but not at +4. 19F-n.m.r. spectra from transcription reactions and gel analysis of transcription products show that T7 RNA polymerase correctly and efficiently utilizes 5-FUTP as a RNA substrate analog. The fluorine atom provides a sensitive probe for monitoring the local environment, base sequence and solvent exposure at the DNA major groove through its 19F-n.m.r. resonance. Buffer dependencies of the fluorine chemical shift and digestion patterns with DNase I suggest that the T7 promoter base-pairs near the transcription start site are distorted with a more open minor groove and less solvent accessible major groove. Previous chemical footprinting data of promoter-polymerase complexes yield a picture that T7 RNA polymerase recognizes major groove features in the region from positions -7 to -11 and minor groove features on the same side of DNA flanking both sides of this region. Consistent with this, 19F-n.m.r. observations identify two additional positions, -8 and -17, involved in promoter recognition on this side of the DNA helix. On the other hand, our observations also implicate the opposite side of the DNA helix, primarily at positions -14 and -15, as major groove recognition sites for T7 RNA polymerase. In addition, n.m.r. spectra from 5-FdU-substituted base-pairs -2 and -3, suggest either additional interactions on the same side of the DNA helix as -14 and -15, or distortions in the DNA structure.

Bacteriophage T7↗
PubMed1993

Genetic complementation reveals a novel regulatory role for 3' untranslated regions in growth and differentiation.

Differentiated skeletal muscle cells cease dividing and sustain expression of a battery of tissue-specific genes. To identify regulators of growth and differentiation, we used a genetic complementation approach. Following introduction of a cDNA expression library into a differentiation-defective myoblast mutant (NMU2), cDNAs were isolated that activated muscle-specific promoters. The complementing cDNAs were identified as muscle structural genes, troponin I, tropomyosin, and alpha-cardiac actin, and their activity was mapped to the 3' untranslated region (3'UTR). The 3'UTRs augmented the differentiation of wild-type muscle cells. Upon expression in 10T1/2 fibroblasts, proliferation was suppressed, indicating that the effects of the 3'UTRs are not limited to myogenic cells. These data suggest that 3'UTRs of certain differentiation-specific RNAs are trans-acting regulators in a feedback loop that inhibits cell division and promotes differentiation.

Actins↗
PubMed1992

Beta-enolase is a marker of human myoblast heterogeneity prior to differentiation.

In this report, we define a muscle-specific marker, beta-enolase, that distinguishes proliferating myoblasts from different stages of development. Enolase exists as multiple isoforms and in the course of cardiac and skeletal muscle development the beta isoform progressively replaces the alpha isoform. In skeletal muscle, this change in gene expression, unlike most developmental changes in myogenic gene expression, is evident in undifferentiated myoblasts. Whereas myoblasts from fetal tissues express alpha-enolase mRNA, beta-enolase is the predominant mRNA expressed by myoblasts from postnatal tissues. Our results are consistent with the idea that distinct precursor myoblasts contribute to the diversity of fiber types characteristic of muscle tissue at different stages of development.

Animals↗
PubMed1990

A tumor suppressor-dependent inhibitor of angiogenesis is immunologically and functionally indistinguishable from a fragment of thrombospondin.

A secreted inhibitor of angiogenesis that is controlled by a tumor suppressor gene in hamster cells has been found to be similar to a fragment of the platelet and matrix protein thrombospondin. The two proteins were biochemically similar and immunologically crossreactive and could substitute for one another in two functional assays. Human thrombospondin inhibited neovascularization in vivo and endothelial cell migration in vitro, as does the hamster protein, gp140. gp140 sensitized smooth muscle cells to stimulation by epidermal growth factor, as does human thrombospondin. The thrombospondin gene has been localized on human chromosome 15. These results demonstrate a function for the ubiquitous adhesive glycoprotein thrombospondin that is likely to be important in the normal physiological down-regulation of neovascularization. In addition, they raise the possibility that thrombospondin may be one of a number of target molecules through which a tumor suppressor gene could act to restrain tumor growth.

Amino Acid Sequence↗
PubMed1989

Regulation of the activity of a new inhibitor of angiogenesis by a cancer suppressor gene.

An inhibitor has been identified in the conditioned medium of hamster cells and hamster-human hybrids that suppresses neovascularization in vivo in the rat cornea. Inhibitory activity was tightly linked to the presence of an active cancer suppressor gene in transformants and revertants, in segregating hybrids, and in temperature-limited transformants. It copurified with a approximately 140 kd glycoprotein. Polyclonal antiserum raised against the purified preparation recognized a 140 kd protein in conditioned medium and was able to adsorb out all antiangiogenic activity. These results define the control of the activity of an inhibitor of neovascularization as one function of the cancer suppressor gene active in BHK21/cl13 cells and simultaneously identify a new inhibitor of angiogenesis, a process vital to the growth of solid tumors.

Angiogenesis Inducing Agents↗
PubMed1989

Anti-tubulin monoclonal antibodies that bind to specific neurons in Caenorhabditis elegans.

We have identified 2 anti-tubulin monoclonal antibodies that bind to 2 different subpopulations of identified neurons in the simple nervous system of the nematode Caenorhabditis elegans. The antibodies also recognize specific tubulin isotypes from C. elegans that were separated by isoelectric focusing. Antibody 6-1 1B-1 intensely stained the mechano-sensory neurons ALML, ALMR, PLML, PLMR, PVM, and AVM, plus neuron PVR by indirect immunofluorescence, and it bound to 1 of 2 major alpha-tubulin isotypes separated by iso-electric focusing. The epitope for antibody (Ab) 6-1 1B-1 is acetylated alpha-tubulin (Piperno and Fuller, 1985). Antibody 2-28-33 stained a set of neurons that contain the neurotransmitter GABA. It bound to the 2 major and 1 of the minor beta-tubulin isotypes of C. elegans. These results suggest that specific alpha- and beta-tubulin isotypes are greatly enriched in the subsets of neurons recognized by these antibodies. Most (possibly all) of the neurons in each subset are functionally related. The antibodies should allow us to examine whether specific tubulin isotypes have specific functions in these neurons. They may also be useful for examining neuron morphologies in mutants of C. elegans which affect nerve development.

Animals↗
PubMed1983

Fungistatic mechanism of human transferrin for Rhizopus oryzae and Trichophyton mentagrophytes: alternative to simple iron deprivation.

Human serum, human transferrin (TF), and the iron chelator 1,10-phenanthroline (OP) produce iron-reversible fungistatic activity which has been attributed to simple iron deprivation. In this study, the influence of the size of the inoculum on the inhibitory activity of serum, TF, and OP prepared with the same iron-binding capacity (2.5 micrograms/ml) for Rhizopus oryzae and Trichophyton mentagrophytes was examined. Inhibition was monitored in liquid microcultures maintained at 37 degrees C and pH 7.4 to 7.5 by measuring the change in absorbance density. Increasing the number of spores in the inoculum disrupted the fungistatic activity of serum and TF, but not that of OP. The dilution at which OP lost fungistatic activity was not affected by the number of spores in the inoculum and was the same for both fungi. The dilution at which TF and serum lost fungistatic activity was dependent upon both the quantity of the inoculum and the species of fungus. The number of viable spores, rather than the total number of spores in the inoculum, was determined to be important in overcoming the inhibition of fungal growth by serum and TF. The fungistatic activity of serum and TF could be diminished by the preexposure of the serum to viable but nongrowing spores. Direct and indirect fluorescence studies indicated that both T. mentagrophytes and R. oryzae absorbed TF. Glucose uptake by R. oryzae was inhibited by a 4-h exposure to 5.0 to 0.15 mg of apotransferrin per ml. These results suggest that the fungistatic activity of TF for R. oryzae and T. mentagrophytes may not be attributable to simple iron deprivation and raise the possibility of a requirement for a direct interaction.

Antifungal Agents↗