HBV surface antigen proteins with deletions in the preS region

Four pairs of HBV surface antigen genes, in which the preS region was partially deleted, were constructed by the polymerase chain reaction (PCR). The comparison of the levels of the expression in mammalian cells of these genes and the ones constructed before, and the properties of these gene products showed that the missing of a part of the preS region did not affect the overall spatial structure of the S region and the surface localization of the preS region. The removal of the preS1 retention sequence (a. a. 2-19) alleviated significantly the shelter of the major antigenic determinants in the S region by the preS sequence. It was found that the long preS region seriously impaired the secretion of the surface antigen proteins from mammalian cells. In addition to the previously reported preS1 retention sequence, the preS1 sequence (a.a. 48-65) may also inhibit the secretion of the surface antigen proteins, whereas the preS2 region exerts no major influence on the retention of the large surface antigen protein. One of the expressed surface antigen proteins, in which the preS1 sequence (a.a. 21-47) and the S region were directly fused, deserves further study and may be developed into a new HBV vaccine which contains the preS1 binding site for hepatocyte receptors due to its stability, fine secretability and strong preS1 antigenicity.

Simple interface for microbore LC and electrospray ionization mass spectrometry and analysis of melphalan-alkylation sites in metallothionein

A microbore high pressure liquid chromatograph has been interfaced to a Vestec electrospray ionization source retrofitted to a Hewlett-Packard quadrupole mass spectrometer. The chief features include the absence of a splitter, the use of a second, ballast column to provide a stable flow rate across the gradient, and an in-line UV detector. The system was evaluated for analysis of peptide mixtures and applied to identification of drug-modified peptides released by tryptic digestion of drug-alkylated metallothionein.

Fibroblasts, mononuclear phagocytes, and endothelial cells express monocyte chemoattractant protein-1 (MCP-1) in inflamed human gingiva

Gingival inflammation is initiated by bacterial colonization of the tooth surface. It is characterized by infiltration of mononuclear cells, a feature of many forms of chronic inflammation. Monocyte chemoattractant protein-1 (MCP-1) is the predominant monocyte chemoattractant secreted by a variety of cells in vitro. We examined MCP-1 expression in chronic gingival inflammation by double antibody immunohistochemistry that utilized rabbit anti-MCP-1 antibody simultaneously with mouse monoclonal antibodies to specific cellular markers. MCP-1 mRNA expression by fibroblasts in inflamed gingival tissues was examined by in situ hybridization. We report here that in human chronic gingival inflammation the principal cell type expressing MCP-1 in dense inflammatory infiltrates is the mononuclear phagocyte. The cells expressing MCP-1 in moderately inflamed areas and in adjacent areas to inflammatory infiltrates are mononuclear phagocytes and fibroblasts, while in areas of fibroblastic hyperplasia, MCP-1 positive cells are predominantly fibroblasts. We also demonstrate that in moderately and highly inflamed areas, the extent of MCP-1 expression is greater than that in adjacent normal/mildly inflamed areas. As the degree of inflammation increased, there is also a concomitant increase in the number of mononuclear phagocytes. Furthermore, it is apparent that most of the infiltrating monocytes/macrophages are positive for MCP-1 in vivo. Our finding that MCP-1 expression is unambiguously identified in fibroblasts suggests that they can play a role in host defense by initiating the recruitment of monocytes. In addition, the expression of chemokines such as MCP-1 may represent a mechanism for amplification of inflammatory signals in gingival inflammation.

Diazepam, given postischemia, protects selectively vulnerable neurons in the rat hippocampus and striatum

Following cerebral ischemia, certain populations of neurons degenerate. Excessive accumulation of excitatory amino acids in the synaptic cleft, activation of excitatory amino acid receptors, and influx of calcium into neurons play a key role in the development of ischemia-induced neuronal death. We hypothesized that neuroprotection may be achieved by enhancing inhibitory (i.e., gamma-aminobutyric acid, GABA) neurotransmission to offset excitation. Diazepam, a drug that increases GABA-induced chloride channel opening, was administered (10 mg/kg, i.p.) to rats 1 and 2 hr following 15 min of transient global ischemia, when hippocampal GABA levels, increased during ischemia, returned to basal. Rats were maintained normothermic during ischemia and became hypothermic following the injections of diazepam. Four days later, rats were sacrificed and the brains were examined for neuronal degeneration and the presence of GABAA receptors labeled by 35S-t-butylbicyclophosphorothionate (35S-TBPS). There was substantial neuroprotection of striatal neurons and pyramidal neurons in the CA1 area of the hippocampus. In addition, diazepam prevented the loss of 35S-TBPS binding sites in the striatum and in the dendritic fields of the CA1 hippocampus following ischemia. Since hypothermia, itself, is neuroprotective, we determined if hypothermia was required for the ability of diazepam to produce neuroprotection. Diazepam was microinjected into the CA1 hippocampus 1 and 2 hr following ischemia, and rats remained normothermic. Four days later, diazepam still produced substantial protection of hippocampal neurons. Thus, postischemic hypothermia may have contributed to the neuroprotection by diazepam when it was administered systemically, but the neuroprotective effect of diazepam did not require hypothermia. We conclude that delayed enhancement of GABAergic neurotransmission directly at the site of vulnerability following an ischemic event protects the vulnerable neurons from death.

Killing of primary CD4+ T cells by non-syncytium-inducing macrophage-tropic human immunodeficiency virus type 1

Understanding the mechanism by which human immunodeficiency virus type 1 (HIV-1) kills CD4+ T lymphocytes is important to the development of therapeutic and prophylactic strategies. Recent studies have indicated that, in some cases, progression to AIDS is associated with the appearance of syncytium-inducing, T cell line-tropic HIV-1 variants. Nevertheless, approximately 50% of subjects with AIDS harbor only non-syncytium-inducing, macrophage-tropic (NSI-M) variants of HIV-1. In most asymptomatic patients, NSI-M HIV-1 isolates are the predominant virus type found. We report here that cytopathicity of NSI-M HIV-1 for primary CD4+ T lymphocytes can be directly detected in vitro. The extent of CD4+ T-cell killing was not completely correlated with the rate of viral replication, suggesting that other characteristics of HIV-1 contribute to its cytopathicity. Our findings suggest that: (i) direct killing by NSI-M HIV-1 may contribute to CD4+ T-lymphocyte depletion in vivo, and (ii) the determinants of HIV-1 cytopathicity for CD4+ T lymphocytes and cell tropism or syncytia-forming ability are not necessarily tightly linked.

Chemical and molecular classification of Saccharomonospora strains

The results of our experiments showed that the 5'-terminal sequences of 23S rRNAs can be used to distinguish different genera of actinomycetes, including the genera Streptomyces, Micromonospora, Amycolatopsis, and Saccharomonospora. There are small differences (< 1%) among the sequences of some strains belonging to the genera Streptomyces (two strains) and Saccharomonospora (seven strains). On the basis of the results of morphological and biochemical analyses, strain 9022 belongs in the genus Saccharomonospora; however, there are distinct differences in the cell wall compositions and the 5' termini of the 23S rRNA sequences of this strain and members of the genus Saccharomonospora. Hence, strain 9022 cannot be classified in the genus Saccharomonospora.

The Escherichia coli RuvB branch migration protein forms double hexameric rings around DNA

The RuvB protein is induced in Escherichia coli as part of the SOS response to DNA damage. It is required for genetic recombination and the postreplication repair of DNA. In vitro, the RuvB protein promotes the branch migration of Holliday junctions and has a DNA helicase activity in reactions that require ATP hydrolysis. We have used electron microscopy, image analysis, and three-dimensional reconstruction to show that the RuvB protein, in the presence of ATP, forms a dodecamer on double-stranded DNA in which two stacked hexameric rings encircle the DNA and are oriented in opposite directions with D6 symmetry. Although helicases are ubiquitous and essential for many aspects of DNA repair, replication, and transcription, three-dimensional reconstruction of a helicase has not yet been reported, to our knowledge. The structural arrangement that is seen may be common to other helicases, such as the simian virus 40 large tumor antigen.

Expression of monocyte chemoattractant protein-1 in delayed type hypersensitivity reactions in the skin

BACKGROUND

Monocyte chemoattractant Protein-1 (MCP-1) is a potent chemotactic factor for monocytes. Because many inflammatory dermatoses are characterized by mononuclear cell infiltrates, it is reasonable to postulate that MCP-1 might be involved in their pathogenesis. To date, no in vivo studies have been published concerning the expression of MCP-1 in this context. The aim of this study was to elucidate the expression of MCP-1 in human inflammatory skin diseases which are thought to involve delayed type hypersensitivity reactions.

EXPERIMENTAL DESIGN

Expression of MCP-1 was examined in normal skin and three classes of inflammatory skin reactions by immunohistochemistry experiments utilizing a monospecific MCP-1 antiserum. The distribution of monocytes/macrophages and T lymphocytes was determined by immunohistochemistry using antibodies to specific cell surface markers.

RESULTS

Immunostaining with MCP-1 antiserum demonstrated strong MCP-1 expression in lichenoid dermatitis, dermal hypersensitivity reactions, and spongiotic dermatitis. In contrast, normal skin showed minimal MCP-1 expression in the dermis. The cell types displaying MCP-1 expression were endothelial cells of dermal microvessels that were surrounded by lymphocytic infiltrates and monocytes/macrophages at the periphery of the perivascular infiltrates. Occasionally, MCP-1-positive mononuclear cells were present both in the infiltrates and in a diffuse pattern in the surrounding dermis. Keratinocytes were found to produce MCP-1 constitutively in normal skin and in inflamed conditions. The pattern of MCP-1 expression was similar to the pattern observed for monocyte/macrophage distribution, whereas the pattern of MCP-1 expression was different from the pattern of T lymphocyte distribution.

CONCLUSIONS

We observed an enhanced expression of MCP-1 in inflammatory skin conditions. The expression of MCP-1 provides a mechanistic explanation for the increased recruitment of monocytes/macrophages in cell-mediated immune response such as delayed type hypersensitivity reactions in the skin.

Mouse hepatitis virus gene 5b protein is a new virion envelope protein

Highly purified radiolabeled mouse hepatitis virus (MHV) A59 contained a previously overlooked protein which coelectrophoreses with the gene 5b product immunoprecipitated from infected cells. The gene 5b protein is post-translationally acylated. Rabbit antibody raised against a recombinant gene 5b protein expressed in Escherichia coli neutralized viral infectivity in the presence of complement, although not in the absence of complement. Immunofluorescent staining of MHV-infected cells with two anti-peptide antibodies revealed that the gene 5b product is membrane-associated and is transported to the cell surface, findings consistent with the prediction of a membrane-spanning segment in the gene 5b polypeptide. These results suggest strongly that the gene 5b polypeptide represents a new MHV virion envelope protein which is homologous to the TGEV ORF 4 and IBV 3c proteins.

Mechanisms of brain injury with deep hypothermic circulatory arrest and protective effects of coenzyme Q10

Sixteen dogs, divided randomly into a control group and coenzyme Q10 group (10mg/kg, intraperitoneally before the operation), underwent deep hypothermic circulatory arrest with cardiopulmonary bypass, as is done clinically. At four time points cerebral cortex and cerebrospinal fluid specimens were collected to study free radical formation, energy metabolism, and ultrastructure. During cardiopulmonary bypass cerebral electron spin resonance spectra and malondialdehyde contents were progressively higher than before bypass, especially at the 60 minutes of circulatory arrest and 30 minutes of reperfusion (p1 < 0.01, p2 < 0.05). In the coenzyme Q10 group at the latter two time points, they had increased less than in the control group at same time points (p1 < 0.02, p2 < 0.005). Adenosine triphosphate content in the cortex during bypass decreased gradually from the prebypass level (p1 < 0.02, p2 = p3 < 0.001), while lactate in cerebrospinal fluid increased (p1 < 0.05, p2 = p3 < 0.001). In the coenzyme Q10 group, adenosine triphosphate at the latter two time points was greater than that in the control group (p1 = p2 < 0.05), while the lactate changes were not significantly different from control at each time point (all p > 0.05). Ultrastructure of the cortex was normal before bypass and almost normal during bypass, but it was obviously abnormal at 60 minutes of circulatory arrest and more seriously abnormal at 30 minutes of reperfusion. In the coenzyme Q10 group the abnormality was obviously reduced. The results suggest that oxygen-derived free radicals and abnormal energy metabolism might play critical roles in brain ischemia/reperfusion injury. Coenzyme Q10 could protect the brain by improving cerebral metabolism.

SIP1 is a catabolite repression-specific negative regulator of GAL gene expression

The yeast Snf1p kinase is required for normal expression of many genes involved in utilization of non-glucose carbon. Snf1p is known to associate with several proteins. One is Sip1p, a protein that becomes phosphorylated in the presence of Snf1p and thus is a candidate Snf1p kinase substrate. We have isolated the SIP1 gene as a multicopy suppressor of the gal83-associated defect in glucose repression of GAL gene expression. Multicopy SIP1 also suppressed the gal82-associated defect in glucose repression, suggesting that SIP1, GAL83 and GAL82 function interdependently. Multicopy SIP1 gene reduces GAL1, GAL2, GAL7 and GAL10 gene expression three- to fourfold in cells grown in the presence of glucose but has no effect in cells grown on nonrepressing carbon. Sip1-deletion cells exhibited a two- to threefold increase in GAL gene expression compared to wild-type cells when grown on glucose. These studies show that SIP1 is a catabolite repression-specific negative regulator of GAL gene expression. Northern analysis revealed two SIP1 transcripts whose relative abundance changed with carbon source. Western blots revealed that Sip1p abundance is not markedly affected by carbon source, suggesting that Sip1p may be regulated post-translationally.

A pK change of acidic residues contributes to cation countertransport in the Ca-ATPase of sarcoplasmic reticulum. Role of H+ in Ca(2+)-ATPase countertransport

Proteoliposomal vesicles reconstituted with sarcoplasmic reticulum ATPase and exogenous lipids sustain ATP-dependent Ca2+ uptake and H+ ejection, as well as net charge displacement by Ca2+. We have studied the effect of lumenal (inner) and medium (extravesicular) pH variations on the countertransport ratios of H+ and Ca2+. We find that the Ca2+/H+ molar ratio is approximately 1 when the lumenal and medium pH is near neutrality, but changes with a specific pattern when the medium pH is varied in the presence of a constant lumenal pH and when the lumenal pH is varied in the presence of a constant medium pH. Empirical analysis of the experimental data shows that the apparent pK of the residue(s) releasing H+ into the medium is approximately 6.1, whereas the apparent pK of the residue(s) binding lumenal H+ is approximately 7.7. Assuming that the same acidic residues are involved in H+ and Ca2+ countertransport, our findings suggest a lower affinity for H+ in their outward orientation (prevalent in the ground state of the enzyme) and a higher affinity for H+ in lumenal orientation (prevalent in the phosphorylated state of the enzyme). Cyclic pK changes, coupled to ATP utilization, promote cation exchange, Ca2+ uptake, and H+ ejection by the vesicles. The stoichiometry of countertransport and net charge displacement is matched by a corresponding electrogenic behavior. A calculation of voltage development related to initial rates of charge transfer (dV/dt = (dQ/dt)/Cm) is given as a corrective replacement of a previous steady state calculation.

An electron-lucent region within the virion distinguishes HIV-1 from HIV-2 and simian immunodeficiency virus

Ultrastructural comparisons of immature or budding particles of human immunodeficiency virus (HIV) types 1 and 2 and simian immunodeficiency virus of macaques (SIVmac) revealed no significant difference between these genetically distinct, but related, viruses. However, a region encompassing the core of mature HIV-1 virions was found to be more electron lucent than that observed in HIV-2 and SIVmac. This ultrastructural distinction cannot be attributed to HIV-1-specific vpu, HIV-2/SIV-specific vpx, or virion-associated vpr gene products.

Postischemic diazepam is neuroprotective in the gerbil hippocampus

In this study, we address the hypothesis that enhancement of gamma-aminobutyric acid (GABA) neurotransmission following an ischemic episode is neuroprotective in the hippocampus. Mongolian gerbils were subjected to transient forebrain ischemia for 5 min by occlusion of the carotid arteries and then administered diazepam (10 mg/kg i.p.) 30 min or 30 and 90 min following ischemia. Diazepam produced a significant decrease in both rectal and brain temperature (4-6 degrees C) in the sham and ischemic gerbils. 1 day following the onset of reperfusion, diazepam substantially reduced the hyperactivity normally induced by the ischemic episode. 7 days later, neuronal viability in the hippocampus was assessed. The single dose of diazepam completely protected the CA1 pyramidal cells of the hippocampus in 62% of the gerbils and the double dose of diazepam completely protected CA1 pyramidal neurons in 67% of the gerbils. There was a significant correlation between the degree of pyramidal cell degeneration in the CA1 area of the hippocampus measured 7 days following ischemia and the degree of hyperactivity measured 1 day following ischemia. Diazepam also prevented the loss of [35S]t-butylbicyclophosphorothionate ([35S]TBPS) binding to GABA-gated chloride channels in the dendritic fields of the CA1 area of the hippocampus. Our findings support the hypothesis that enhancement of GABA neurotransmission following an ischemic event may offset neuronal excitability and prevent neuronal death in specific brain regions. We conclude that GABA-enhancing drugs, such as diazepam, are attractive candidates as neuroprotective agents following ischemic insults.

Monoclonal antibodies to Afipia felis--a putative agent of cat scratch disease

Twelve hybridoma clones producing monoclonal antibodies to Afipia felis, a putative causative agent of cat scratch disease, were derived from BALB/c mice immunized with A felis. All 12 monoclonal antibodies were species-specific for A felis and reacted with lipopolysaccharide antigens of A felis. These monoclonal antibodies belong to immunoglobulin (Ig) G1, IgG2a, IgG2b, IgG3, and IgM isotypes. All monoclonal antibodies reacted with both agar-grown A felis and tissue culture-propagated A felis. Formalin fixation did not alter the reactivity of the antigen with the monoclonal antibodies. These monoclonal antibodies could be a useful tool for investigation of the disputed role of A felis in cat scratch disease.

The effect of temperature and pH on the solubility of quinolone compounds: estimation of heat of fusion

Although many reports involving fluoroquinolone agents have been published in the past decades, only a few address preformulation studies. In this paper, we describe the effect of temperature and pH on the aqueous solubility of two typically used quinolones, ciprofloxacin and norfloxacin. We measured the aqueous solubilities over the pH range of 5.5 to 9.5 at temperature of 6, 25, 30, and 40 degrees C. The intrinsic solubilities and the thermodynamic dissociation constants were determined from solubility data and the temperature dependence of the intrinsic solubility was evaluated using van't Hoff and Hildebrand plots. The heat of fusion was determined from these two plots. When the heat of fusion was compared to that measured from differential scanning calorimetry (DSC) studies, we found that the Hildebrand method overestimated, and the van't Hoff equation underestimated, the heat of fusion. From the absolute values of the relative errors, the Hildebrand plot produced the better results. DSC results show that the heat of fusion is 15.41 kcal/mol for ciprofloxacin and 7.88 kcal/mol for norfloxacin.

Serotyping Coxiella burnetii isolates from acute and chronic Q fever patients by using monoclonal antibodies

Four mouse monoclonal antibodies reacting with Coxiella burnetti lipopolysaccharide antigens were produced and used in serotyping 17 C. burnetii isolates from acute Q fever and Q fever endocarditis patients in France. Two monoclonal antibodies (1B2 and 3B6) were considered specific for the Priscilla strain, a representative of Q fever endocarditis isolates, and did not react with the Nine Mile strain, which is representative of acute Q fever isolates. Monoclonal antibodies Nos. 1B2 and 3B6 reacted with 75% (3/4) acute Q fever isolates and 85% (11/13) of endocarditis isolates from France. It is reasonable to conclude that Priscilla-like strains cause both acute Q fever and Q fever endocarditis. The hypothesis that Priscilla-like strains only are associated with Q fever endocarditis should be reconsidered.

[Free thyroxine in burn patient and its clinical significance]

Using radioimmunoassay serum FT3 and FT4 and S-TSH were determined in 42 patients with different sizes of burn. The results were all in the normal range, indicating that there was only sufficient amount of thyroxine in trauma patients to maintain the lowest basal metabolism for living. The changes in the total T3 and T4 did not conform to that reported elsewhere. It deserves further clinical observation and study.

Differentiation among spotted fever group rickettsiae species by analysis of restriction fragment length polymorphism of PCR-amplified DNA

Restriction fragment length polymorphism (RFLP) analysis of PCR-amplified genes was used to study spotted fever group (SFG) rickettsiae, extending the previous work of Regnery et al. (R.L. Regnery, C.L. Spruill, and B.D. Plikaytis, J. Bacteriol. 173:1576-1589, 1991). Twenty-six strains of SFG rickettsia were studied, including several recognized species which have never been studied (R. parkeri, R. helvetica, and R. japonica) as well as strains which are not currently classified. Two previously used primer pairs derived from the R. prowazekii citrate syntase gene and the R. rickettsii 190-kDa protein antigen gene were studied, as were primer pairs obtained from the R. rickettsii 120-kDa protein antigen gene. By using three amplifications and three enzyme digestions, it was possible to differentiate between almost all of the known SFG rickettsia species and to differentiate between several strains of the R. conorii complex. Two human pathogens, "R. africae" and the Israeli tick typhus rickettsia, were first separated by using BG-12 pair primer amplification and then RsaI restriction endonuclease digestion. The proposed simplified model of identification may be useful in studying the geographical distributions of SFG rickettsiae.

Bidirectional modulation of GABA-gated chloride channels by divalent cations: inhibition by Ca2+ and enhancement by Mg2+

The effects of the divalent cations Ca2+, Sr2+, Ba2+, Mg2+, Mn2+, and Cd2+ were studied on gamma-aminobutyric acidA (GABAA) responses in rat cerebral cortical synaptoneurosomes. The divalent cations produced bidirectional modulation of muscimol-induced 36Cl- uptake consistent with their ability to permeate and block Ca2+ channels. The order of potency for inhibition of muscimol responses was Ca2+ > Sr2+ > Ba2+, similar to the order for permeation of Ca2+ channels in neurons. The order of potency for enhancement of muscimol responses was Cd2+ > Mn2+ > Mg2+, similar to the order for blockade of Ca2+ channels in neurons. Neither Ca2+ nor Mg2+ caused accumulation of GABA in the extravesicular space due to increased GABA release or decreased reuptake of GABA by the synaptoneurosomes. The inhibition of muscimol responses by Ca2+ was most likely via an intracellular site of action because additional inhibition could be obtained in the presence of the Ca2+ ionophore, A23187. This confirms electrophysiologic findings in cultured neurons from several species. In contrast, the effects of Cd2+, Mn2+, and Mg2+ may be mediated via blockade of Ca2+ channels or by intracellular sites, although the results of these studies do not distinguish between the two loci. The effects of Zn2+ were also studied, because this divalent cation is reported to have widely divergent effects on GABAA responses. In contrast to other studies, we demonstrate that Zn2+ inhibits GABAA responses in an adult neuronal preparation. Zn2+ produced a concentration-dependent inhibition (limited to 40%) of muscimol responses with an EC50 of 60 microM. The inhibition of muscimol-induced 36Cl- uptake by Zn2+ was noncompetitive.(ABSTRACT TRUNCATED AT 250 WORDS)

Three-dimensional reconstruction of a co-complex of F-actin with antibody Fab fragments to actin's NH2 terminus

We have decorated F-actin with Fab fragments of antibodies to actin residues 1-7. These antibody fragments do not strongly affect the rigor binding of myosin S-1 to actin, but do affect the binding of S-1 to actin in the presence of nucleotide (DasGupta, G., and E. Reisler, 1989. J. Mol. Biol. 207:833-836; 1991. Biochemistry. 30:9961-9966; 1992. Biochemistry. 31:1836-1841). Although the binding constant is rather low, we estimate that we have achieved about 85% occupancy of the actin sites. Three-dimensional reconstructions from electron micrographs of both negatively stained and frozen-hydrated filaments show that the Fab fragment is bound at the location of the NH2 terminus in the model of Holmes et al. (Holmes, K.C., D. Popp, W. Gebhard, and W. Kabsch. 1990. Nature. 347:37-44) for F-actin, excluding very different orientations of the actin subunit in the filament. Most of the mass of the antibody is not visualized, which is due to the large mobility of the NH2 terminus in F-actin, differences in binding angle within the polyclonal antibody population, or a combination of both of these possibilities.

Characterization and regulation of the protein binding to a cis-acting element, RET 1, in the rat opsin promoter

RET 1 is a binding site for retinal nuclear proteins located at -136 to -110 bp in the rat opsin promoter, as defined by DNase protection assays. A similar sequence is found in the upstream flanking regions of many other photoreceptor genes in mammals and other species, including Drosophila. A 7-base consensus sequence, CAATTAG, is found in these genes and has the binding activity of the longer RET 1 element. A 40-kDa protein that binds to RET 1 has been purified over 2 x 10(5)-fold to apparent homogeneity by affinity chromatography. The RET 1 binding activity is first detectable at E18 and increases during the first two postnatal weels, At embryonic ages the retarded bands show an altered mobility and at early postnatal ages two bands are detected, with the adult band increasing and the embryonic band decreasing in intensity. Treatment of early postnatal retinas with bFGF increased the binding activity in nuclear extracts and caused a shift in migration of the retarded band to a position characteristic of the embryonic form of the complex. The results support the hypothesis that RET 1-like elements play an important role in rod photoreceptor development.

A cis-acting element, T alpha-1, in the upstream region of rod alpha-transducin gene that binds a developmentally regulated retina-specific nuclear factor

The G protein transducin (T) is an integral component of the signal transduction pathway in photoreceptors. We have identified a cis-acting element, T alpha-1, in the upstream region of the mouse rod alpha-T (Tr alpha) gene that may be important for tissue-specific expression. T alpha-1 binds a retina-specific nuclear factor of apparent molecular mass of 90 kDa. Binding to the T alpha-1 site is developmentally regulated and peaks between postnatal days 6 and 9. This corresponds to the time of rod photoreceptor maturation and the rise in Tr alpha gene expression. The sequence of T alpha-1 shows homology with RET-1, a cis-acting element in the proximal promoter of opsin gene that binds a distinct retina-specific factor. T alpha-1 and RET-1 sequences may have been derived from a prototype T alpha-1/RET-1 sequence, evolved to confer photoreceptor specificity on retina-specific genes.