Detection of anticentromere antibodies using recombinant human CENP-A protein

OBJECTIVE

To evaluate CENP-A reactivity with anticentromere antibodies (ACA) using recombinant protein (rCENP-A).

METHODS

Human CENP-A antigen was overexpressed in insect cells using the baculovirus system. We tested for ACA activity against the full-length recombinant polypeptide by immunoblot and by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Of the ACA+ sera studied (n = 38), 95% were positive when tested against the rCENP-A in the ELISA system. Of the ACA- sera (n = 100), only 2% gave false-positive results in the assay. There was good correlation between the recombinant and bona fide antigens in assaying for ACA reactivity.

CONCLUSION

CENP-A is a significant ACA target. The availability of the rCENP-A assay is a valuable adjunct to the previously described rCENP-B assay in analyses of the clinical significance of ACA.

Human CENP-A contains a histone H3 related histone fold domain that is required for targeting to the centromere

Centromeres are the differentiated chromosomal domains that specify the mitotic behavior of chromosomes. To examine the molecular basis for the specification of centromeric chromatin, we have cloned a human cDNA that encodes the 17-kD histone-like centromere antigen, CENP-A. Two domains are evident in the 140 aa CENP-A polypeptide: a unique NH2-terminal domain and a 93-amino acid COOH-terminal domain that shares 62% identity with nucleosomal core protein, histone H3. An epitope tagged derivative of CENP-A was faithfully targeted to centromeres when expressed in a variety of animal cells and this targeting activity was shown to reside in the histone-like COOH-terminal domain of CENP-A. These data clearly indicate that the assembly of centromeres is driven, at least in part, by the incorporation of a novel core histone into centromeric chromatin.

LKM-1 autoantibodies recognize a short linear sequence in P450IID6, a cytochrome P-450 monooxygenase

LKM-1 autoantibodies, which are associated with autoimmune chronic active hepatitis, recognize P450IID6, a cytochrome P-450 monooxygenase. The reactivities of 26 LKM-1 antisera were tested with a panel of deletion mutants of P450IID6 expressed in Escherichia coli. 22 sera recognize a 33-amino acid segment of P450IID6, and 11 of these recognize a shorter segment, DPAQPPRD. PAQPPR is also found in IE175 of herpes simplex virus type 1 (HSV-1). Antibodies for HSV-1 proteins were detected by ELISA in 17 of 20 LKM-1 sera tested. An immobilized, synthetic peptide, DPAQPPRDC, was used to purify LKM-1 antibodies. Affinity purified LKM-1 autoantibodies react on immunoblots with a protein in BHK cells after infection with HSV-1. 11 of 24 LKM-1 sera, including 3 that recognize DPAQPPRD, also exhibit antibodies to the hepatitis C virus (HCV) protein, C100-3. Affinity purified LKM-1 antibodies did not recognize C100-3. However, partial sequence identity was evident between portions of the immunopositive 33-amino acid segment of P450IID6 and other portions of the putative HCV polyprotein. Immune cross-recognition of P450IID6 and HCV or HSV-1 proteins may contribute to the occurrence of LKM-1 autoantibodies.

CENP-B is a highly conserved mammalian centromere protein with homology to the helix-loop-helix family of proteins

CENP-B is a centromere associated protein originally identified in human cells as an 80 kDa autoantigen recognized by sera from patients with anti-centromere antibodies (ACA). Recent evidence indicates that CENP-B interacts with centromeric heterochromatin in human chromosomes and may bind to a specific subset of human alphoid satellite DNA. CENP-B has not been unambiguously identified in non-primates and could, in principal, be a primate-specific alphoid DNA binding protein. In this work, a human genomic DNA segment containing the CENP-B gene was isolated and subjected to DNA sequence analysis. In vitro expression identified the site for translation initiation of CENP-B, demonstrating that it is encoded by an intronless open reading frame (ORF) in human DNA. A homologous mouse gene was also isolated and characterized. It was found to possess a high degree of homology with the human gene, containing an intronless ORF coding for a 599 residue polypeptide with 96% sequence similarity to human CENP-B. 5' and 3' flanking and untranslated sequences were conserved at a level of 94.6% and 82.7%, respectively, suggesting that the regulatory properties of CENP-B may be conserved as well. CENP-B mRNA was detected in mouse cells and tissues and an immunoreactive nuclear protein identical in size to human CENP-B was detected in mouse 3T3 cells using human ACA. Analysis of the sequence of CENP-B revealed a segment of significant similarity to a DNA binding motif identified for the helix-loop-helix (HLH) family of DNA binding proteins. These data demonstrate that CENP-B is a highly conserved mammalian protein that may be a member of the HLH protein family and suggest that it plays a role in a conserved aspect of centromere structure or function.

The epidemiology of germinal matrix hemorrhage during the first half-day of life

The personal and maternal characteristics of 27 babies with early-onset germinal matrix hemorrhage (EGMH) were compared with those of 280 babies with normal cranial ultrasonograms, studied in a separate clinical trial. None of the mothers of the babies with EGMH had high blood pressure or pre-eclampsia during pregnancy. Gestational age less than 30 weeks and initial pH less than 7.2 indicated increased risks of EGMH, and maternal receipt of steroids indicated reduced risk of EGMH. Thus prenatal and immediately perinatal factors appear to convey much of the information about the risk of EGMH.

Optimization of routine transformation of Escherichia coli with plasmid DNA

Methods to optimize resources and transformation efficiency of routine daily transformations of DH1 Escherichia coli prepared by three calcium chloride methods were investigated and compared with polyethylene glycol and Hanahan methods. The benefit of a heat-shock step, a preplating incubation step to allow expression of antibiotic resistance, use of log phase bacteria and prolonged storage of bacteria were investigated using pBR322 and pUC18 plasmid DNAs. Bacteria prepared by CaCl2 methods consistently gave efficiencies of 4 x 10(6) transformants/microgram of plasmid DNA or better and were overall the most labor- and resource-efficient methods. Use of log phase bacteria, a heat shock and an incubation step were found to be beneficial for freshly prepared bacteria for all methods. Prolonged storage of up to 30 days of bacteria prepared by the CaCl2 methods was beneficial, resulting in a sustained increase in transformation efficiency when selection was by ampicillin but not when by tetracycline resistance. Also found when using bacteria stored three days or longer was an increased transformation efficiency of stationary vs. log phase bacteria and an unchanged or even increased efficiency when the preplating incubation step was omitted. The Hanahan methods were the most labor and resource intensive and routinely gave efficiencies of 2 x 10(7). Higher efficiencies of 10(8) were obtained only with repeated trial and error and were not consistently reproducible. The polyethylene glycol method consistently gave efficiencies of 2 x 10(7), and bacteria could easily be prepared daily or frozen with a minimal decrease in efficiency.

Insights into native epitopes of proliferating cell nuclear antigen using recombinant DNA protein products

A cDNA clone encoding full-length human proliferating cell nuclear antigen (PCNA) was used to generate a panel of in vitro translated labeled protein products with COOH-terminal deletions and to construct a set of fusion proteins with COOH- and NH2-terminal deletions. A rabbit antiserum raised against an NH2-terminal peptide, a well-characterized murine monoclonal antibody (mAb), and 14 human lupus sera with autoantibody to PCNA were analyzed for their reactivity with the constructs using both immunoprecipitation and immunoblotting techniques. The rabbit antiserum reacted in immunoprecipitation and immunoblotting with constructs containing the appropriate NH2-terminal sequence and mAb reacted with a sequence from the midregion of PCNA. These experimentally induced antibodies also reacted with 15-mer synthetic peptides in enzyme-linked immunosorbent assay (ELISA). In contrast, none of the lupus sera reacted with synthetic peptides in ELISA. 9 of the 14 lupus sera also failed to react in Western immunoblotting with any recombinant fusion protein, although they all immunoprecipitated in vitro translated full-length protein. Four of the nine had variable patterns of immunoprecipitation with shorter constructs. The remaining five lupus sera were able to immunoprecipitate translation products as well as Western blot recombinant fusion proteins. From analysis of the patterns of reactivity of human lupus sera, it was deduced that the apparent heterogeneity of human autoantibodies to PCNA could be explained by immune response to highly conformational epitopes. These observations demonstrate that there might be special features in "native" epitopes of intranuclear antigens that are recognized by autoantibodies, and that these special features of native epitopes might not be present in prepared antigen used for experimental immunization. These features may be related to protein folding or to association of the antigen with other intranuclear proteins or nucleic acids, as might occur with antigens that are components of subcellular particles.

Patients with type II autoimmune hepatitis express functionally intact cytochrome P-450 db1 that is inhibited by LKM-1 autoantibodies in vitro but not in vivo

Liver-kidney microsomal-1 autoantibodies characterize a subgroup of autoimmune chronic active hepatitis. The liver antigen of liver-kidney microsomal-1 antibodies has been identified as cytochrome P450 db1, a microsomal enzyme catalyzing the oxidative metabolism of more than 20 drugs, including debrisoquine, sparteine and bufuralol. A genetic polymorphism (debrisoquin-sparteine polymorphism) is responsible for the lack of P450 db1 protein in the livers of 5% to 10% of Caucasians, leading to impaired drug metabolism and a distinct poor metabolizer phenotype. We investigated whether liver-kidney microsomal-1 positive autoimmune chronic active hepatitis patients express functionally intact P450 db1 in their livers. In four patients with liver-kidney microsomal-1 positive chronic active hepatitis, but not in five patients with various liver-kidney microsomal-1 negative liver diseases, the presence of circulating liver-kidney microsomal-1 antibodies was confirmed by immunofluorescence, radioimmunoassay and immunoblotting analysis using recombinant P450 db1. Moreover, only sera from liver-kidney microsomal-1 positive autoimmune chronic active hepatitis patients strongly inhibited the enzymatic activity of P450 db1 in human liver microsomes in vitro. Immunoblotting detected 50-kd P450 db1 protein in liver biopsy specimens from all patients. The in vivo function of P450 db1 was investigated by determining the metabolic ratio for sparteine and its 2-dehydro and 5-dehydro metabolites in 12-hr urine samples after oral administration of sparteine sulfate. In vivo P450 db1-mediated drug metabolism was of the extensive metabolizer phenotype and did not differ significantly between liver-kidney microsomal-1 positive (metabolic ratio = 1.15 +/- 0.32) and liver-kidney microsomal-1 negative (metabolic ratio = 1.18 +/- 0.48) patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Periventricular-intraventricular hemorrhage, sonographic localization, phenobarbital, and motor abnormalities in low birth weight infants

A total of 228 low birth weight (less than 1750 g), mechanically ventilated infants with and without periventricular-intraventricular hemorrhage were examined at 18 months corrected age to assess the relationship between cranial ultrasonographic findings and specific motor abnormalities. All infants were previously enrolled in a double-blind, randomized, prospective clinical trial of phenobarbital prophylaxis against periventricular-intraventricular hemorrhage. Ultrasonographic abnormalities on the scans performed between 7 and 13 days of life were categorized as germinal matrix hemorrhage, lateral ventricular hemorrhage, parenchymal hemorrhage, ventriculomegaly, and any hemorrhage. Regardless of anatomical location, periventricular-intraventricular hemorrhage was associated with an increased risk for developing motor abnormalities. Hypertonia and hyperreflexia/ankle clonus were most common. No abnormal motor findings distinguished unilateral from bilateral germinal matrix hemorrhage and lateral ventricular hemorrhage or between phenobarbital and placebo treatment. None of the 5 infants with parenchymal hemorrhage had spastic cerebral palsy. Ventriculomegaly was associated with a fivefold increase in risk for spastic cerebral palsy and delayed walking and a threefold increase for hypertonia and hyperreflexia/clonus. The results suggest that ventriculomegaly, observed even as early as the first week of life, might be a significant antecedent of later motor abnormalities among the survivors of periventricular-intraventricular hemorrhage.

In vitro posttranslational modification of lamin B cloned from a human T-cell line

Autoimmune diseases are characterized by spontaneously occurring autoantibodies which have proven to be useful reagents for the characterization of specific nuclear proteins. Using a monoclonal autoantibody (72B9) derived from a murine lupus strain, we have cloned a cDNA from the human T-cell line MOLT-4, which encodes nuclear lamin B. The identity of the encoded protein as lamin B was established by both biochemical and immunological criteria. Inspection of the deduced amino acid sequence of lamin B revealed the presence in coil 1B of the alpha-helical domain of a leucine heptad repeat region. Analysis of mRNA in HL60 and MOLT-4 cells, which express only lamin B, or HeLa cells, which express all three major lamins (A, B, and C), together with the comigration of in vitro-translated product with isolated HeLa cell lamin B by two-dimensional gel electrophoresis, suggests that a single lamin B is expressed in mammalian somatic cells. In vitro translation with the cDNA clone revealed an EDTA-sensitive posttranslational modification which resulted in an increase in the apparent molecular weight to that equivalent to the native in vivo-synthesized lamin B protein. This in vitro modification included incorporation of a product of mevalonolactone and required an intact carboxy terminus.

Sjögren's syndrome nuclear antigen B (La): cDNA cloning, structural domains, and autoepitopes

SS-B/La is a major antigenic target for autoantibodies in patients with Sjögren's syndrome. Its transient association with nascent RNA polymerase III transcripts in the cell nucleus suggest a functional role of SS-B/La in RNA processing and maturation. Human SS-B/La autoantibodies recognize at least two distinct epitopes on two separate structural domains of the SS-B/La protein and these epitopes are conserved among mammalian species. In contrast, murine monoclonal antibodies produced though immunization with purified bovine SS-B/La recognize different epitopes. To elucidate these differences, cDNA sequences of SS-B/La were cloned from several mammalian species including human, bovine, and rabbit. Complete human SS-B/La cDNAs including the coding sequence (1227bp) and untranslated sequences were isolated. The complete bovine sequence was determined from two overlapping partial cDNA clones. Comparison of the complete protein sequences encoded by the human and bovine cDNAs revealed a high degree of conservation of amino acid sequence showing only 26 substitutions/deletions out of 408 residues. RNA blot analysis indicated the presence of two size species of transcripts in bovine and rabbit cells, 1.8 kb and greater than 2.5 kb, in contrast to a single 1.8 kb mRNA species in human cells. The results of cDNA cloning support our previous finding of SS-B/La as a two-domain protein, and the RNA-binding site is confirmed to be located within N-terminal domain designated X. Epitope mapping using recombinant SS-B/La fusion proteins confirmed the findings of at least two autoepitopes located on different domains.

Isolation and characterization of a cDNA clone encoding the 60-kD component of the human SS-A/Ro ribonucleoprotein autoantigen

SS-A/Ro is a nucleocytoplasmic ribonucleoprotein (RNP) particle that is a common target of autoimmune response in Sjögren's syndrome (SS) and systemic lupus erythematosus (SLE). Previously, SS-A/Ro has been shown to be composed of at least two polypeptide antigens of 60 and 52 kD noncovalently associated with a set of small RNAs, designated Y1-Y5. A serum from an SS patient was selected to screen a lambda gt11 cDNA library constructed from human T cell lymphoblastic leukemia (MOLT-4) mRNA. An immunoreactive clone was isolated that possessed a 1.8-kb cDNA insert. In vitro transcription and translation of the cDNA resulted in the synthesis of a 57.5-kD polypeptide which was specifically immunoprecipitated by SS-A/Ro antisera. The identity of the cDNA encoded protein as the 60-kD SS-A/Ro antigen was established by proteolytic peptide mapping of the cDNA-encoded protein and the 60-kD HeLa cell antigen. The sequence of the cDNA shows that the 60-kD SS-A/Ro protein possesses both RNA binding protein consensus sequences and a single zinc-finger motif. Recombinant SS-A/Ro antigen produced in bacteria proved to be a sensitive and specific reagent for detection of anti-SS-A/Ro antibodies in patient sera. The availability of the 60-kD SS-A/Ro cDNA will enable detailed analysis of the molecular structure and function of the SS-A/Ro RNP particle and its role in autoimmune pathology.

Ribonucleoprotein SS-B/La belongs to a protein family with consensus sequences for RNA-binding

Autoantibodies from systemic rheumatic disorders have become useful reagents in molecular biology. SS-B/La, a major target of autoantibodies in lupus and Sjogren's syndrome, has been identified as a 46 kDa protein component of a ribonucleoprotein (RNP) particle implicated in the maturation of RNA polymerase III transcripts. This report describes the complete sequences of human and bovine SS-B/La and the identification of RNA-binding protein consensus sequences RNP1 and RNP2 in the N-terminal region previously shown to be complexed with RNA in UV-crosslinking experiments. Segments of about 95 residues from the RNA-binding domain of SS-B/La and from 29 RNA-binding domains of several other proteins are analysed with respect to the frequency of amino acids and their hydrophobicity at each position. The data suggest that SS-B/La belongs to a large family of RNA-binding proteins which includes heterogeneous nuclear RNPs, nucleolin, mRNA polyadenylate binding protein, and small nuclear RNPs.

Major antigen of liver kidney microsomal autoantibodies in idiopathic autoimmune hepatitis is cytochrome P450db1

Type 1, liver kidney microsomal autoantibodies (LKM-1) are associated with a subgroup of idiopathic autoimmune type, chronic active hepatitis (CAH). The antigenic specificity of LKM-1 autoantibodies from 13 patients was investigated by immunoblot analysis of human liver microsomal proteins. Polypeptides of 50, 55, and 64 kD were detected with these antisera. A high titer LKM-1 serum was selected to screen a human liver lambda gt11 cDNA expression library, resulting in the isolation of several complementary (c)DNA clones. Autoantibodies affinity purified from proteins expressed by two of the immunopositive cDNA clones, HLD8.2 and HLD13.2, specifically react with a 50-kD protein of human liver microsomes and display immunofluorescence staining of the proximal renal tubular epithelia characteristic of LKM-1 sera. Determination of the sequence of HLD8.2 revealed that it encodes a recently described cytochrome P450db1. A bacterial fusion protein constructed from HLD8.2 proved to be a specific and sensitive diagnostic reagent. All sera from patients with LKM-1 positive liver disease react with this fusion protein. No reaction was seen, however, for sera from patients with other types of autoimmune liver diseases, viral hepatitis, systemic immunological disorders, or healthy controls.

Hemorrhage, phenobarbital, and fluctuating cerebral blood flow velocity in the neonate

Fifty-one sequential intubated babies with birth weights of less than 1,751 were evaluated by serial Doppler ultrasound during the first three days of life. These babies were part of a phenobarbital prophylaxis trial cohort study. Subependymal-intraventricular hemorrhage developed in 17 of the babies. Infants with subependymal-intraventricular hemorrhage, whether or not they received pancuronium or phenobarbital, had coefficients of variation comparable to those of babies without hemorrhage. Coefficient of variation values of the right were comparable to values obtained from the left anterior cerebral artery complex and did not appear to be consistently altered by the presence of subependymal-intraventricular hemorrhage. Coefficient of variation values appeared to be consistently greatest on day 1 and lowest on day 2. In addition, the values overall increased as the number of waves used to determine the coefficient of variation enlarged from five to 20. This phenomena, however, was not seen among pancuronium recipients and suggests that movement artifact may be a determinant of coefficient of variation values. We conclude that, when the best 20 waves are chosen to evaluate the coefficient of variation, no association exists between coefficient of variation values and development of subependymal-intraventricular hemorrhage or administration of phenobarbital.

Bilirubin, intraventricular hemorrhage, and phenobarbital in very low birth weight babies

The relationships among serum bilirubin concentration on days 5 and 7, birth weight, the presence of intraventricular hemorrhage, and the receipt of phenobarbital were examined in a group of 232 newborns weighing less than 1,751 g who were intubated, mechanically ventilated by 12 hours after birth, and whose parents had given permission for a randomized trial of phenobarbital prophylaxis of intraventricular hemorrhage. The ratio of serum bilirubin concentration to birth weight (the bilirubin divided by birth weight index [BBI]) was used to examine the impact of 25 variables on a clinical guideline for therapy of hyperbilirubinemia in newborn infants. A linear regression model was used; the most powerful covariate was a birth weight less than 1.0 kg. The only other variable that reduced the BBI was phenobarbital receipt. The presence of intraventricular hemorrhage and ecchymoses had a significant influence increasing the BBI.

A 52-kD protein is a novel component of the SS-A/Ro antigenic particle

Anti-SS-A/Ro autoantibodies are found in the sera of patients with Sjogren's syndrome (SS) and SLE. In the course of analyzing 61 SS patients for their autoantibody profiles, we found that 42 were positive for anti-SS-A by double diffusion in agarose and demonstrated precipitin lines identical to that produced by a prototype anti-SS-A serum. Further analysis of these SS-A antibody-positive sera by Western blotting of cell extracts revealed that 21 sera reacted with two proteins of 60 and 52 kD, 13 sera reacted with 52-kD protein, two detected only 60 kD, while six were nonreactive. Affinity-purified anti-60-kD and anti-52-kD antibodies reacted exclusively with their corresponding antigens. Partial proteolysis of these proteins did not reveal common degradation fragments. Thus the 52- and 60-kD proteins were found to be antigenically and apparently structurally distinct from each other. They were also distinct from 48-kD SS-B/La protein. In immunoprecipitation using labeled cell extracts, affinity-purified anti-52-kD antibodies brought down the 52-kD protein as well as the 60-kD band. In [32P]orthophosphate-labeled HeLa cell extract both antibodies precipitated the same spectrum of small RNAs (hYl-5). In indirect immunofluorescence, anti-52-kD and anti-60-kD antibodies immunolocalized in similar subcellular structures and showed similar punctate nuclear staining patterns. Western blot analysis revealed that both proteins were present in lymphocytic as well as epithelial human cell lines tested. The data above define a new antigen of 52 kD which is another component of the SS-A particle and is associated in complex formation with the previously reported 60-kD protein.

Antinuclear antibodies (ANAs): diagnostically specific immune markers and clues toward the understanding of systemic autoimmunity

The convergence of studies in the clinical and basic sciences has resulted in the definitive identification of many intracellular antigens which are the targets of autoantibodies in patients with systemic lupus erythematosus, scleroderma, dermatomyositis/polymyositis, Sjogren's syndrome, mixed connective tissue disease, and drug-induced autoimmunity. Some of this new knowledge includes the identification of the Sm and RNP antigens as ribonucleoprotein particles involved in splicing of precursor messenger RNA, Scl-70 as DNA topoisomerase I, proliferating cell nuclear antigen as auxiliary protein of DNA polymerase delta, and certain antigens in myositis as aminoacyl transfer RNA synthetases. This information confirms, at a molecular level, the presence of specific profiles of autoimmune responses so that autoantibodies can be used in clinical medicine as diagnostically useful immune markers. In addition the data give compelling reasons to consider that certain autoimmune diseases are antigen-driven. Many auto-antibodies have the interesting feature of recognizing epitopes on the antigens which are active or functional sites of the molecule. It is suggested that the data provide clues to the nature of the intracellular particle initiating the immune response and may help to elucidate some of the early mechanisms of the autoimmune process.

Arterial blood gas derangements associated with death and intracranial hemorrhage in premature babies

We evaluated to what extent acidosis and alkalosis and their respiratory and metabolic components during the first 12 hours of life occurred prior to early neonatal death and postnatal intracranial hemorrhage among 206 low birth weight, intubated premature babies participating in a clinical trial of phenobarbital prophylaxis for intracranial hemorrhage. Time-weighted indices included the time each baby spent with abnormal values of pH, PaCO2 and HCO3-. Babies whose birth weight was less than 1 kg suffered adversities associated with prolonged pH less than 7.35. Heavier birth weight babies were at increased risk of adversity if their pH fell below 7.2. Babies who were not severely acidotic initially, but became so within hours, were at prominently increased risk of death and hemorrhage. Babies who had a mild increase of PaCO2 between 45 and 60 mmHg were less likely to develop germinal matrix hemorrhage than their peers who had more severe hypercapnia. A time-weighted measure of metabolic deficit correlated with death, but not with hemorrhage. Prolonged exposure to pH greater than 7.55 was associated with reduced risk of subependymal/intraventricular hemorrhage and death, especially in babies below 1 kg birth weight. We conclude that acidosis is an antecedent of intracranial hemorrhage in low birth weight premature babies, that duration of exposure might convey important risk information, and that birth weight is a correlate of vulnerability to some pH disturbances.

Respiratory complications in low-birth-weight infants who received phenobarbital

We compared the ventilatory requirements of 127 infants who received phenobarbital for five days with those of 111 infants who received placebo. All infants were intubated, weighted less than 1750 g at birth, and survived the first ten days of life. Those infants who received phenobarbital did not require ventilatory assistance for more days than did placebo receivers. However, a pneumothorax or pulmonary interstitial emphysema was more likely to develop in infants who received phenobarbital than in infants who received placebo, even when adjustment was made for the presence of subependymal-intraventricular hemorrhage. We believe this is the first report of this relationship and recommend additional studies to test the hypothesis that phenobarbital contributes to the occurrence/recognition of pneumothorax or pulmonary interstitial emphysema in very-low-birth-weight infants if phenobarbital continues to be used routinely as prophylaxis or treatment.

Molecular cloning of cDNA for CENP-B, the major human centromere autoantigen

We have isolated a series of overlapping cDNA clones for approximately 95% of the mRNA that encodes CENP-B, the 80-kD human centromere autoantigen recognized by patients with anticentromere antibodies. The cloned sequences encode a polypeptide with an apparent molecular mass appropriate for CENP-B. This polypeptide and CENP-B share three non-overlapping epitopes. The first two are defined by monoclonal antibodies elicited by injection of cloned fusion protein. Epitope 1 corresponds to a major antigenic site recognized by the anticentromere autoantibody used to obtain the original clone. Epitope 2 is a novel one not recognized by the autoantibody. These epitopes were shown to be distinct both by competitive binding experiments and by their presence or absence on different subcloned portions of the fusion protein. The third independent epitope, recognized by a subset of anticentromere-positive patient sera, maps to a region substantially closer to the amino terminus of the fusion protein. DNA and RNA blot analyses indicate that CENP-B is unrelated to CENP-C, a 140-kD centromere antigen also recognized by these antisera. CENP-B is the product of a 2.9-kb mRNA that is encoded by a single genetic locus. This mRNA is far too short to encode a polypeptide the size of CENP-C. The carboxy terminus of CENP-B contains two long domains comprised almost entirely of glutamic and aspartic acid residues. These domains may be responsible for anomalous migration of CENP-B on SDS-polyacrylamide gels, since the true molecular mass of CENP-B is approximately 65 kD, 15 kD less than the apparent molecular mass deduced from gel electrophoresis. Quite unexpectedly, immunofluorescence analysis using antibodies specific for CENP-B reveals that the levels of antigen vary widely between chromosomes.

Sequence and expression of the chicken beta 5- and beta 4-tubulin genes define a pair of divergent beta-tubulins with complementary patterns of expression

We have determined the nucleotide sequence of the chicken beta 5 (c beta 5)-tubulin gene. The gene displayed the coding structure common to all previously studied vertebrate beta-tubulin genes and was divided into four exon sequences interrupted by three intervening sequences (located between codons 19 and 20, within codon 56, and within codon 93). Comparison of the predicted polypeptide sequence encoded by c beta 5 with those of four other available chicken beta-tubulin sequences revealed that c beta 5 encoded a highly divergent beta-tubulin polypeptide isotype which was distinguished from previously known sequences primarily by two discrete variable sequence domains. However, c beta 5 uniquely shared identity in 16 residue positions with another divergent chicken beta-tubulin gene, c beta 4. These common sequences distinguished c beta 4 and c beta 5 from the remaining three chicken beta-tubulin genes. Analysis of the expression of c beta 5 and c beta 4 revealed a strikingly complementary pattern of gene expression: c beta 5 was expressed in a wide variety of cell and tissue types but not in neurons, whereas c beta 4 expression was detected uniquely in neuronal cells. Overall, these findings suggest the existence of two divergent families of beta-tubulin sequences in the chicken and further raise the possibility that the complementary expression of the c beta 4 and c beta 5 genes may fulfill a requirement for the presence of a divergent beta-tubulin polypeptide isotype in all cell types.

Sequence and expression of the chicken beta 3 tubulin gene. A vertebrate testis beta-tubulin isotype

We report the determination of the complete DNA sequence for c beta 3, a chicken beta-tubulin gene which we show to be the dominant beta-tubulin expressed in testis. Like all previously studied vertebrate beta-tubulin genes, the gene is divided into four exon sequences interrupted by three intervening sequences (located between amino acids 19 and 20, within codon 56, and within codon 93). Analysis of the program of expression of this gene indicates that it encodes the dominant chicken testis beta-tubulin, although it is also expressed at lower levels in a wide variety of cell and tissue types. Comparison of the predicted polypeptide sequence for c beta 3 with four other available chicken beta-tubulin genes confirms our earlier suggestion that within an otherwise conserved framework, sequences within two variable region domains serve to define specific beta-tubulin polypeptide isotypes. The data indicate that the c beta 3 gene encodes a unique beta-tubulin isotype which diverges from the dominant neuronal beta-tubulin isotype in 18 of 445 residues (4%). Although the protein coding regions of the c beta 3 gene are highly homologous to the chicken c beta 1, c beta 2, c beta 4, and c beta 5 genes previously reported by us, no significant sequence homology with these previously analyzed genes is discernible in the 5'- or 3'-untranslated region sequences, in the intervening sequences, or in the presumptive transcriptional promoter sequences.