Biomedical subjects

N D L'Etoile

Publications and source records attributed to N D L'Etoile.

6 recordsLinked to original sources

PubMed2001

Polarized dendritic transport and the AP-1 mu1 clathrin adaptor UNC-101 localize odorant receptors to olfactory cilia.

Odorant receptors and signaling proteins are localized to sensory cilia on olfactory dendrites. Using a GFP-tagged odorant receptor protein, Caenorhabditis elegans ODR-10, we characterized protein sorting and transport in olfactory neurons in vivo. ODR-10 is transported in rapidly moving dendritic vesicles that shuttle between the cell body and the cilia. Anterograde and retrograde vesicles move at different speeds, suggesting that dendrites have polarized transport mechanisms. Residues immediately after the seventh membrane-spanning domain of ODR-10 are required for localization; these residues are conserved in many G protein-coupled receptors. UNC-101 encodes a mu1 subunit of the AP-1 clathrin adaptor complex. In unc-101 mutants, dendritic vesicles are absent, ODR-10 receptor is evenly distributed over the plasma membrane, and other cilia membrane proteins are also mislocalized, implicating AP-1 in protein sorting to olfactory cilia.

Amino Acid Sequence↗

PubMed2000

Olfaction and odor discrimination are mediated by the C. elegans guanylyl cyclase ODR-1.

Animals in complex environments must discriminate between salient and uninformative sensory cues. Caenorhabditis elegans uses one pair of olfactory neurons called AWC to sense many different odorants, yet the animal can distinguish each odorant from the others in discrimination assays. We demonstrate that the transmembrane guanylyl cyclase ODR-1 is essential for responses to all AWC-sensed odorants. ODR-1 appears to be a shared signaling component downstream of odorant receptors. Overexpression of ODR-1 protein indicates that ODR-1 can influence odor discrimination and adaptation as well as olfaction. Adaptation to one odorant, butanone, is disrupted by ODR-1 overexpression. Olfactory discrimination is also disrupted by ODR-1 overexpression, probably by overproduction of the shared second messenger cGMP. We propose that AWC odorant signaling pathways are insulated to permit odor discrimination.

Adaptation, Physiological↗

PubMed1995

Core promoter-specific function of a mutant transcription factor TFIID defective in TATA-box binding.

In conjunction with other general initiation factors, the TATA box-binding protein (TBP) can direct basal transcription by RNA polymerase II from TATA-containing promoters, but its stable interaction with TBP-associated factors (TAFs) in the TFIID complex is required both for activator-dependent transcription and for basal transcription directed by an initiator element. We have generated a TATA-binding-defective TFIID complex containing an amino acid substitution in the DNA-binding surface of its TBP subunit. This mutated TFIID is defective in both basal and activated transcription from core promoters containing only a TATA box but supports transcription from initiator-containing promoters independently of the presence or absence of a TATA sequence. Our results show that a functional initiator element is needed to bypass the requirement for an active TATA DNA-binding surface in TFIID and imply that gene-specific transcription can be achieved by modulating distinct core promoter-specific TFIID functions--e.g., TBP-TATA versus TAF-initiator interactions.

Amino Acid Sequence↗

PubMed1994

Human transcription factor IIIC box B binding subunit.

Transcription factor IIIC (TFIIIC) is a multisubunit basic TF for RNA polymerase III. It initiates transcription complex assembly on tRNA and related genes by binding to the internal box B promoter element and is also required for transcription of 5S rRNA and other stable nuclear and cytoplasmic RNAs transcribed by polymerase III. In mammalian cells, regulation of TFIIIC activity controls overall polymerase III transcription in response to growth factors and viral infection. Here, we report the cloning and sequencing of a full-length cDNA (and genomic DNA from the transcription initiation region) encoding the box B binding subunit of human TFIIIC, the 243-kDa alpha subunit. Specific antisera raised against the encoded protein super shifts a TFIIIC-box B DNA complex during an electrophoretic mobility shift assay and immunodepletes TFIIIC transcriptional activity from a partially purified TFIIIC fraction, proving that the cDNA encodes a component of TFIIIC. The human protein shows surprisingly little similarity to the box B binding subunit of yeast TFIIIC.

Amino Acid Sequence↗

PubMed1989

A DNA-binding domain of human transcription factor IIIC2.

Transcription factor IIIC2 is required for in vitro transcription of the adenovirus 2 VA1 gene and binds with high affinity to its B-box promoter element which is an 18 bp perfect inverted repeat. Partial proteolysis of TFIIIC2 with chymotrypsin and Staphylococcus aureus V8 protease yielded a species which produced a discrete band in a gel shift assay with about twice the mobility of the undigested complex. Chymotrypsin-digested TFIIIC2 produced a DNase I footprint virtually identical to that of the undigested protein, but the stability of the protein-VA1 DNA complex was drastically reduced and the in vitro transcriptional activity was eliminated. These results indicate that a chymotrypsin-resistant domain of TFIIIC2 binds to the B-box sequence. We speculate that stable binding requires protease sensitive cooperative interactions between TFIIIC2 DNA-binding domains.

Adenoviruses, Human↗

PubMed1989

Purification and characterization of transcription factor IIIC2.

Transcription factor IIIC2 (TFIIIC2), together with other transcription factors (TFIIIB and TFIIIC1), is required for the in vitro transcription of tRNA and adenovirus VA genes by RNA polymerase III. Previous studies have shown that TFIIIC2 is a high molecular weight (approximately 500,000) protein which binds with high affinity to the B-box promoter element of tRNA-type genes. A polypeptide of Mr approximately 250,000 is in close association with DNA in the specific complex between TFIIIC2 and the B-box promoter element. Here we describe the purification of TFIIIC2 by a factor of approximately 25,000 from nuclear extracts of HeLa cells by ionic exchange, affinity, and hydrophobic chromatography and sedimentation velocity centrifugation. The most purified fractions contain polypeptides of approximately 230 kDa (corresponding to the polypeptide which can be cross-linked to VA1 DNA), 110, 100, 80, and 60 kDa which co-sediment with TFIIIC2 B-box specific binding and in vitro transcriptional activities.

Adenoviruses, Human↗