Localization of a myosin heavy chain-like polypeptide to Drosophila nuclear pore complexes.

Antibodies previously used for immunofluorescence localization of a myosin heavy chain-like polypeptide to the nuclear envelope in higher eukaryotic cells crossreact with both muscle and nonmuscle isoforms of Drosophila myosin heavy chain. Analyses of Drosophila tissue culture cells and premyogenic embryos suggest that it is the nonmuscle isoform that is associated with the nuclear envelope. Further immunofluorescence and immunoelectron microscopy indicate that this polypeptide is associated with nuclear pore complexes. These data support the hypothesis put forward previously that myosin or myosin-like molecules play a role in pore complex architecture.

A beta-spectrin isoform from Drosophila (beta H) is similar in size to vertebrate dystrophin.

Spectrins are a major component of the membrane skeleton in many cell types where they are thought to contribute to cell form and membrane organization. Diversity among spectrin isoforms, especially their beta subunits, is associated with diversity in cell shape and membrane architecture. Here we describe a spectrin isoform from Drosophila that consists of a conventional alpha spectrin subunit complexed with a novel high molecular weight beta subunit (430 kD) that we term beta H. The native alpha beta H molecule binds actin filaments with high affinity and has a typical spectrin morphology except that it is longer than most other spectrin isoforms and includes two knoblike structures that are attributed to a unique domain of the beta H subunit. Beta H is encoded by a different gene than the previously described Drosophila beta-spectrin subunit but shows sequence similarity to beta-spectrin as well as vertebrate dystrophin, a component of the membrane skeleton in muscle. By size and sequence similarity, dystrophin is more similar to this newly described beta-spectrin isoform (beta H) than to other members of the spectrin gene family such as alpha-spectrin and alpha-actinin.

Purification of Drosophila hsp 83 and immunoelectron microscopic localization.

Heat-shock protein (hsp) 83 was purified from Drosophila culture cells. Analysis by gel filtration revealed that this hsp exists in a dimeric form under nondenaturing conditions. Monoclonal and polyclonal antibodies produced against this hsp have been used to determine its intracellular localization by indirect immunofluorescence and immunogold electron microscopy in normal cells, after heat shock, during recovery and after a second heat shock. Under normal conditions, hsp 83 is predominantly cytoplasmic. Immunogold labeling reveals that this hsp is associated with vacuole-like structures containing numerous dense bodies. In addition, hsp 83 is detected, albeit at a lower level, in the nucleus where it is found within the network of perichromatin ribonucleoprotein (RNP) fibrils. This distribution changes during heat shock: hsp 83 is then found in increased concentrations at the cell periphery close to the plasma membrane. After a recovery period, hsp 83 appears associated with the nuclear membrane and/or with the neighboring endoplasmic reticulum. Following a second heat shock at 37 degrees C after recovery, a renewed deposition of hsp 83 is observed at the cell periphery. A small population of cells also shows an increased concentration of this protein in the nucleus. This intracellular distribution of hsp 83 is consistent with its reported association with various cellular proteins and suggest that this hsp may be involved in their intracellular transport and/or in the modulation of their activity.

Enhancement of tyrosine kinase activity of the Drosophila epidermal growth factor receptor homolog by alterations of the transmembrane domain.

The Drosophila epidermal growth factor receptor homolog (DER) displays sequence similarity to both the epidermal growth factor (EGF) receptor and the neu vertebrate proteins. We have examined the possibility of deregulating the tyrosine kinase activity of DER by introducing structural changes which mimic the oncogenic alterations in the vertebrate counterparts. Substitution of valine by glutamic acid in the transmembrane domain, in a position analogous to the oncogenic mutation in the rat neu gene, elevated the in vivo kinase activity of DER in Drosophila Schneider cells sevenfold. A chimera containing the oncogenic neu extracellular and transmembrane domains and the DER kinase region, also showed a threefold elevated activity relative to a similar chimera with normal neu sequences. Double truncation of DER in the extracellular and cytoplasmic domains, mimicking the deletions in the v-erbB oncogene, did not however result in stimulation of in vivo kinase activity. The chimeric constructs were also expressed in monkey COS cells, and similar results were obtained. The ability to enhance the DER kinase activity by a specific structural modification of the transmembrane domain demonstrates the universality of this activation mechanism and strengthens the notion that this domain is intimately involved in signal transduction. These results also support the inclusion of DER within the tyrosine-kinase receptor family.

Structural and functional features of Drosophila chorion proteins s36 and s38 from analysis of primary structure and infrared spectroscopy.

Amino acid composition, Fourier transform analysis and secondary structure prediction methods strongly support a tripartite structure for Drosophila chorion proteins s36 and s38. Each protein consists of a central domain and two flanking 'arms'. The central domain contains tandemly repetitive peptides, which apparently generate a secondary structure of beta-sheet strands alternating with beta-turns, most probably, forming a twisted beta-pleated sheet or beta-barrel. The central domains of s36 and s38 share similarities, but they are recognizably different. The flanking 'arms', with different primary and secondary structure features, presumably serve protein-specific functions. The possible roles of the protein domains for the establishment of higher order structure in Drosophila chorion and the possible function of the molecules are discussed. The predicted secondary structure of Drosophila chorion proteins s36 and s38 is supported by experimental information obtained from Fourier transform infrared spectroscopic studies of Drosophila chorions.

Examination of protein sequence homologies. VI. The evolution of Escherichia coli L7/L12 equivalent ribosomal proteins ('A' proteins), and the tertiary structure.

Sequence homologies among 23 complete and two partial sequences of ribosomal 'A' proteins from eukaryotes, metabacteria, eubacteria and chloroplasts, equivalent to Escherichia coli L7/L12, were examined using a correlation method that evaluates sequence similarity quantitatively. Examination of 325 comparison matrices prepared for possible combinations of the sequences indicates that 'A' protein sequences can be classified into two types: one is the "prototype" from eubacteria and chloroplasts, and the other is the "transposition type" from eukaryotes and metabacteria, which must have resulted from the internal transposition of the prototype sequence. The transposition type of eukaryotes can further be classified into P1 and P2 lines. Sequences of the P1 line are closer to those of metabacteria than to those of the P2 line. Eleven gaps, as deletion or insertion sites of amino acid residues, are necessary for an alignment of all the sequences. According to the crystallographic data for the C-terminal fragment (CTF) from E. coli L7, all the gaps involved in the CTF are located between segments that correspond to structural and functional elements such as alpha helix, beta strand, turning loop or hinge part. The existence of specific "preservation units" in these molecules is suggested. In contrast, the transposition site is located at the center of an alpha helix element that is involved in a folding domain, indicating that the transposition event was extremely drastic.

An antibody to the Drosophila period protein recognizes circadian pacemaker neurons in Aplysia and Bulla.

The molecular mechanisms of the pacemakers underlying circadian rhythms are not well understood. One molecule that presumably functions in the circadian clock of Drosophila is the product of the period (per) gene, which dramatically affects biological rhythms when mutated. An antibody specific for the per protein labels putative circadian pacemaker neurons and fibers in eyes of two marine gastropods, Aplysia and Bulla. As was found for the Drosophila per protein, there is a daily rhythm in the levels of the per-like antigen in Aplysia eyes. Thus, certain molecular features of the per protein, as well as aspects of the temporal regulation of its expression, may be conserved in circadian pacemakers of widely divergent species.

Drosophila basement membrane procollagen IV. I. Protein characterization and distribution.

A collagen was isolated from Drosophila E85, Schneider line 2L and Kc cell cultures. The purified protein was characterized and antibodies were raised against it. Immunofluorescence microscopy locates this material to the regions of basement membranes of Drosophila embryos, larvae, and adults. The molecules are mostly, or entirely, homotrimers of one polypeptide chain linked by interchain disulfide bonds. The partial amino acid sequences of a cyanogen bromide cleavage product of this chain are identical with a part of the virtual translation product of the Drosophila pro alpha 1(IV) nucleotide sequence that is reported in the accompanying paper. This gene is at Drosophila chromosome location 25C and was identified by the high homology of one part of it with the noncollagenous carboxyl terminus (NC1) of vertebrate type IV basement membrane collagens (Blumberg, B., MacKrell, A. J., Olson, P. F., Kurkinen, M., Monson, J. M., Natzle, J. E., and Fessler, J. H. (1987) J. Biol. Chem. 262, 5947-5950). In the electron microscope each molecule appears as a thread with a knob at one end, which contains the carboxyl peptide domains. The variation of flexibility of the thread was mapped along its length. Pulse-chase labeling of cell cultures showed that these molecules associate into disulfide-linked dimers and higher oligomers that can be partly separated by velocity sedimentation and are resolved by sodium dodecyl sulfate-agarose gel electrophoresis. Dimers and higher oligomers formed by overlap of the amino ends of molecules were found. Mild pepsin digestion of Drosophila embryos and larvae solubilized the corresponding disulfide-linked collagen molecules, and Staphylococcus aureus V8 protease peptide maps showed the identity of the collagen derived from animals and from cell cultures. Individual, native molecules have a sedimentation coefficient s20,w = 4.1 S, the dichroic spectrum and amino acid composition of a collagen, and a Tm = 31 degrees C. Positive in situ hybridization with a specific probe for this collagen began 6-8 h after egg laying and showed message in the locations of embryos and larvae which reacted with the antibodies. This included some prominent individual cells in the hemolymph.

Octopus rhodopsin. Amino acid sequence deduced from cDNA.

The primary structure of rhodopsin from the octopus Paroctopus defleini has been determined by parallel analysis of the protein and corresponding cDNA. The amino acid sequence is most similar to the recently cloned Drosophila opsins. Similarities to bovine and human opsins are also evident. The transmembrane topology of octopus rhodopsin is discussed.

Members of the Drosophila HSP 70 family share ATP-binding properties.

In Drosophila, the hsp 70 family consists of a group of proteins of similar molecular masses (hsps 68, 70 and 72) that exist as multiple isoforms. In this report, it is shown that hsps 68, 70 and 72 from Drosophila cells can be purified by affinity chromatography on ATP-agarose. Furthermore it is demonstrated that the multiple members of the hsp 70 family, which accumulate in large amounts in the nucleus during a heat shock, can be specifically solubilized from the isolated nuclei fraction by ATP. One of the major cognate proteins (hsc 70) also shows similar behavior. These data suggest that most, if not all, of the related Drosophila hsps 70 possess, like their mammalian counterparts, an ATP-binding site which could be related to their function in the stress response.

Comparative biochemical and immunological analysis of the three vitellogenins from Drosophila grimshawi.

1. The three female-specific vitellogenin proteins, namely V1, V2 and V3, have been isolated and characterized from Drosophila grimshawi. Their mol. wt, as determined by SDS-polyacrylamide gel electrophoresis are 46,000, 45,000 and 43,000 which are in agreement with those determined by Ferguson plot analysis. 2. All three vitellogenins appear to be monomers in the ovarian extracts and they have very similar biochemical and immunological properties. 3. Ion-exchange chromatography, double immunodiffusion tests and partial digestion with Staphylococcus aureus V8 protease indicated more physicochemical and structural similarities between the V1 and the V2 polypeptides. 4. The distribution pattern of the proteolytic polypeptides resulting from limited chymotrypsin digestion suggested partial homology in the primary structure of the three vitellogenin proteins.

Papilin: a Drosophila proteoglycan-like sulfated glycoprotein from basement membranes.

A sulfated glycoprotein was isolated from the culture media of Drosophila Kc cells and named papilin. Affinity purified antibodies against this protein localized it primarily to the basement membranes of embryos. The antibodies cross-reacted with another material which was not sulfated and appeared to be the core protein of papilin, which is proteoglycan-like. After reduction, papilin electrophoresed in sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a broad band of about 900,000 apparent molecular weight and the core protein as a narrow band of approximately 400,000. The core protein was formed by some cell lines and by other cells on incubation with 1 mM 4-methylumbelliferyl xyloside, which inhibited formation of the proteoglycan-like form. The buoyant density of papilin in CsCl/4 M guanidine hydrochloride is 1.4 g/ml, that of the core protein is much less. Papilin forms oligomers linked by disulfide bridges, as shown by sodium dodecyl sulfate-agarose gel electrophoresis and electron microscopy. The protomer is a 225 +/- 15-nm thread which is disulfide-linked into a loop with fine, protruding thread ends. Oligomers form clover-leaf-like structures. The protein contains 22% combined serine and threonine residues and 25% combined aspartic and glutamic residues. 10 g of polypeptide has attached 6.4 g of glucosamine, 3.1 g of galactosamine, 6.1 g of uronic acid, and 2.7 g of neutral sugars. There are about 80 O-linked carbohydrate chains/core protein molecule. Sulfate is attached to these chains. The O-linkage is through an unidentified neutral sugar. Papilin is largely resistant to common glycosidases and several proteases. The degree of sulfation varies with the sulfate concentration of the incubation medium. This proteoglycan-like glycoprotein differs substantially from corresponding proteoglycans found in vertebrate basement membranes, in contrast to Drosophila basement membrane laminin and collagen IV which have been conserved evolutionarily.

Satellite DNA-correlated nucleosomal proteins in Drosophila virilis.

Three major satellite DNAs comprise 40-45% of the genome of Drosophila virilis. Since these satellites are not substrates for most restriction enzymes, we were able to digest D. virilis nuclei with HaeIII and micrococcal nuclease and isolate chromatin fractions containing variable levels of satellite DNA. Electrophoretic analysis of these chromatin fractions revealed that the level of the acid-soluble chromosomal protein, cp17.3, was directly related to the percentage of satellite DNA in chromatin. The correlation between cp17.3 and satellite DNA abundance suggests that cp17.3 is involved in the heterochromatic condensation of satellite DNAs. cp17.3 occurs at a frequency of one molecule per 10-20 nucleosomes. It is detected in an electrophoretically distinguishable class of mononucleosomes, provisionally identified as MN1uH2A, which contains ubiquitinated histone H2A (uH2a) but lacks histone H1. It is not detected in MN1, a second class of mononucleosomes, which lacks uH2A and H1. Since cp17.3 is correlated with satellite DNAs and present in nucleosome cores, it might be a histone variant specifically associated with satellite DNAs.

Localization of the fushi tarazu protein during Drosophila embryogenesis.

The fushi tarazu (ftz) gene of Drosophila acts early in embryogenesis to regulate body segmentation. The localization of the ftz protein product in embryos was examined using indirect immunofluorescence microscopy. Antibodies were prepared against a beta-galactosidase-ftz hybrid protein made in E. coli. The ftz protein was first detectable in blastoderm-stage embryos as seven stripes of nuclei encircling the embryos transversely. The stripes persist through the early events of gastrulation, but disappear before overt segmentation is visible. The ftz protein is expressed a second time in some nuclei of the developing nervous system. In contrast to the early pattern, at the later stage, ftz is expressed in each of fifteen metameric subunits of the embryo.

F-actin rings are associated with the ring canals of the Drosophila egg chamber.

Staining of Drosophila egg chambers with rhodaminyl-lysine-phallotoxin (RLP), a specific stain for F-actin, has demonstrated the presence of dense F-actin rings associated with the inner surfaces of the ring canals. They were first observed in the distal part of the germarium where rings of four different size classes were found, differing in diameter by up to twofold. The ring sizes are considered to correspond to the ring canals formed at each of four successive incomplete cleavages. During the growth of the egg chamber the actin rings were found to increase in diameter from less than 1 micron to approx. 10 micron. Concomitantly a secondary outer ring of more diffuse material is built up in association with the cell membranes. A well developed array of microfilament bundles was also associated with the nurse cell plasmalemma. In stages where the transfer of the bulk of the nurse cell cytoplasm into the oocyte was occurring the rings came closer together in a central area. In late stage chambers the F-actin rings and the microfilament bundles appeared to be incorporated into large irregular masses of actin, which subsequently disappeared as the mature oocyte formed. The F-actin rings are suggested to act as mechanical strengthening elements for the canal plasmalemma, whilst cytoplasmic transport occurs through the ring canals.

A further characterization of Drosophila cuticular monoenes using a mass spectrometry method to localize double bonds in complex mixtures.

Positions of double bonds of olefins of complex mixtures, such as those of Drosophila cuticular hydrocarbons, have been determined using a simple method combining methoxymercuration-demercuration of extracts and analysis by gas chromatography-mass spectrometry using ammonia for chemical ionization. Chemical similarities between cuticular monoenes of both sexes of Drosophila simulans and males of Drosophila melanogaster are specified: the major isomer is always in position 7.

Is the major Drosophila heat shock protein present in cells that have not been heat shocked?

When eukaryotic cells are exposed to elevated temperatures they respond by vigorously synthesizing a small group of proteins called the heat shock proteins. An essential element in defining the role of these proteins is determining whether they are unique to a stressed state or are also found in healthy, rapidly growing cells at normal temperatures. To date, there have been conflicting reports concerning the major heat-induced protein of Drosophila cells, HSP 70. We report the development of monoclonal antibodies specific for this protein. These antibodies were used to assay HSP 70 in cells incubated under different culture conditions. The protein was detectable in cells maintained at normal temperatures, but only when immunological techniques were pushed to the limits of their sensitivity. To test for the possibility that these cells contain a reservoir of protein in a cryptic antigenic state (i.e., waiting posttranslational modification for use at high temperature), we treated cells with cycloheximide or actinomycin D immediately before heat shock. HSP 70 was not detected in these cells. Finally, we tested for the presence of a reservoir of inactive messages by using a high stringency hybridization of 32P-labeled cloned gene sequences to electrophoretically separated RNAs. Although HSP 70 mRNA was detectable in rapidly growing cells, it was present at less than 1/1,000th the level achieved after induction.