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D Resendez-Perez

Publications and source records attributed to D Resendez-Perez.

6 recordsLinked to original sources
PubMed1998

Spatial and temporal targeting of gene expression in Drosophila by means of a tetracycline-dependent transactivator system.

In order to evaluate the efficiency of the tetracycline-regulated gene expression system in Drosophila, we have generated transgenic lines expressing a tetracycline-controlled transactivator protein (tTA), with specific expression patterns during embryonic and larval development. These lines were used to direct expression of a tTA-responsive promoter fused to the coding region of either the beta-galactosidase or the homeotic protein Antennapedia (ANTP), under various conditions of tetracycline treatment. We found that expression of beta-galactosidase can be efficiently inhibited in embryos and larvae with tetracycline provided in the food, and that a simple removal of the larvae from tetracycline exposure results in the induction of the enzyme in a time- and concentration-dependent manner. Similar treatments can be used to prevent the lethality associated with the ectopic expression of ANTP in embryos and, subsequently, to control the timing of expression of the homeoprotein ANTP specifically in the antennal imaginal disc. Our results show that the expression of a gene placed under the control of a tetracycline-responsive promoter can be tightly controlled, both spatially by the regulatory sequences driving the expression of tTA and temporally by tetracycline. This provides the basis of a versatile binary system for controlling gene expression in Drosophila, with an additional level of regulation as compared to the general method using the yeast transcription factor GAL4.

Animals↗
PubMed1994

Nuclear magnetic resonance solution structure of the fushi tarazu homeodomain from Drosophila and comparison with the Antennapedia homeodomain.

The three-dimensional structure of a recombinant 70-residue polypeptide containing the complete fushi tarazu (ftz) homeodomain from Drosophila melanogaster has been determined by nuclear magnetic resonance (NMR) spectroscopy in solution. On the basis of 915 upper distance constraints derived from nuclear Overhauser effects and 178 dihedral angle constraints, a group of 20 conformers representing the solution structure of the ftz homeodomain was computed with the program DIANA and energy-minimized with the program OPAL. The average of the pairwise root-mean-square deviations of the individual NMR conformers relative to the mean coordinates is 0.50 A for the backbone atoms N, C alpha and C' of residues 8 to 53. The molecular architecture includes three helices comprising the residues 10 to 21, 28 to 38, and 42 to 52, a loop of residues 22 to 27 between the helices I and II, and a turn of residues 39 to 41 linking the helices II and III. Comparisons with the structure of the mutant Antennapedia homeodomain with Cys39 replaced by Ser, Antp (C39S), shows that the two proteins contain the same molecular fold for residues 8 to 53, whereas the more flexible fourth helix comprising residues 53 to 59 in the Antp (C39S) homeodomain has no counterpart in the ftz homeodomain. Considering that important intermolecular interactions in the DNA complexes with the Antp, engrailed and Mat alpha 2 homeodomains involve the fourth helix, it was rather unexpected that the stability of the complex of ftz with the BS2 operator site was found to be comparable to or even somewhat higher than that of the Antp complex with BS2. Another difference is that the Antp homeodomain is more stable with respect to thermal denaturation, with denaturation temperatures at pH 4.8 of 27 degrees C and 48 degrees C, respectively, for ftz and Antp.

Amino Acid Sequence↗
PubMed1994

The des(1-6)antennapedia homeodomain: comparison of the NMR solution structure and the DNA-binding affinity with the intact Antennapedia homeodomain.

The nuclear magnetic resonance (NMR) solution structure of an N-terminally truncated mutant Antennapedia homeodomain, des(1-6)Antp(C39S), has been determined from 935 nuclear Overhauser effect upper distance constraints and 148 dihedral angle constraints by using the programs DIANA and OPAL. Twenty conformers representing the solution structure of des(1-6)Antp(C39S) have an average root-mean-square distance relative to the mean coordinates of 0.56 A for the backbone atoms of residues 8-59. Comparison with the intact Antp(C39S) homeodomain shows that the two proteins have identical molecular architectures. The removal of the N-terminal residues 1-6, which are flexibly disordered in the intact homeodomain, causes only strictly localized structure variations and does not noticeably affect the adjoining helix I from residues 10-21. The DNA-binding constant of des(1-6)Antp(C39S) is approximately 10-fold reduced relative to the intact Antp(C39S) homeodomain, which can now be attributed to the absence of the previously reported contacts of the N-terminal polypeptide segment of the intact Antp(C39S) homeodomain with the minor groove of the DNA duplex.

Amino Acid Sequence↗
PubMed1991

The human placental lactogen genes: structure, function, evolution and transcriptional regulation.

hPL is a member of an evolutionarily related gene family including hGH and hPRL. Expression of hPL is limited to the placenta but its physiological actions are far reaching. hPL has a direct somatotropic effect on fetal tissues, it alters maternal carbohydrate and lipid metabolism to provide for fetal nutrient requirements, and aids in stimulation of mammary cell proliferation. Two hPL genes (hPL3 and hPL4) encoding identical proteins are responsible for the production of up to 1-3 g PL hormone/day. Recent studies have characterized the regulatory controls of hPL expression. At the post transcriptional level, RNA stability may contribute to variable levels of hPL3 vs. hPL4 production. In addition, non-tissue-specific protein-promoter interactions involving the Sp1 transcription factor are necessary for hPL transcription initiation. A transcriptional enhancer located 3' to the hPL3 gene is responsible for the placenta-specific expression of this gene, while an additional enhancer may be located 3' to the hPl4 gene. The hPL enhancer is bound by multiple proteins including at least one placental specific protein that interacts with a TEF-1 motif. Therefore, enhancer-protein interactions most likely play a large part in the high levels of placenta-specific hPL expression.

Amino Acid Sequence↗
PubMedDate not supplied

Low-speed purification of human placental nuclei.

A simple method for the purification of human placental nuclei is described. Nuclei were isolated by homogenizing tissue in standard saline citrate solution in the presence of zinc chloride to stabilize the nuclear membranes, NP40 as non-ionic detergent and sodium bisulphite for inhibition of proteolytic activity. Nuclei purification was achieved by low-speed centrifugation through a discontinuous sucrose gradient. The purified nuclei were evaluated by morphological criteria using phase contrast and electron microscopy. The extent of contamination by cytoplasmic debris was estimated by Papanicolaou's staining technique. Biochemical criteria include measurements of alkaline phosphatase activity as a plasma membrane enzyme marker and DNA-dependent RNA polymerase activity for the functional integrity of nuclear components. Transcriptionally active nuclei were obtained but the yield of nuclei was low; however, this low yield is compensated by the high degree of purity, the simplicity of the method and the functional and morphological integrity of the purified nuclei.

Alkaline Phosphatase↗