Gagging and cooperation in 4-12-year-old children over a series of dental appointments

PURPOSE

The purposes were to evaluate if gagging can affect children's cooperation with treatment, investigate possible changes in gagging and study factors that can predict children's behaviour over dental treatment.

METHODS

255 children aged 4-12 years, needing at least three consecutive dental appointments, completed the Children's Fear Survey Schedule-Dental Subscale before examination. The Gagging Problem Assessment was performed before the initial examination and after the third/final appointment. Frankl's Behaviour Rating Scale (FBRS) was used to rate children's behaviour. Multivariate Mixed Linear and Logistic Regression Models were used.

RESULTS

Children with definitely positive behaviour were significantly older, less fearful and less likely to gag before treatment. Girls and older children had lower odds of gagging over time, while fearful children had higher odds. There were no statistically significant associations between gagging over time, FBRS and the type of dental treatment at the third appointment. The percentage of children who gagged after the third appointment (27.05%) was significantly lower as compared to the percentage found at the initial appointment (32.54%; p = 0.004).

CONCLUSION

Among the variables studied, age, dental fear, initial GPA and type of treatment were good predictors of children's behaviour during dental treatment.

Factors associated with gagging during radiographic and intraoral photographic examinations in 4-12-year-old children

AIMS

No studies are available in paediatric samples evaluating gagging during toothbrushing, radiographic and/or intraoral photographic examinations. The aims were to collectively examine potential factors associated with gagging during radiographs and intraoral photographs in 4-12-year-old children.

METHODS

Parents/guardians of 395 children (aged 4-12 years old) completed questionnaires asking about their children's toothbrushing habits. Children completed Greek versions of the Gagging Assessment Scale (GAS) and the Children's Fear Survey Schedule-Dental Subscale (CFSS-DS), while the dentist used the shorter version of the Gagging Problem Assessment (GPA-de-c/SF) to objectively assess gagging. X-ray and Photo Rating Scales were created to evaluate gagging during X-rays and photographs, respectively. Multivariate logistic regression was used to examine the relationship between the potential factors and gagging.

RESULTS

59 of 275 patients (21%) and 56 of 276 patients (20%) who needed X-rays and intraoral photographs, respectively, gagged. Children who gagged during X-rays had significantly higher GAS scores (p = 0.007). Boys, younger children, and those who gagged on GPA-de-c/SF were more likely to gag during X-rays, and children who gagged on GPA-de-c/SF were more likely to gag during photographs. Brushing habits were not related to dental fear or gagging.

CONCLUSION

Of the variables which we studied, GPA-de-c/SF most strongly affected the odds of gagging during taking radiographs and/or intraoral photographs.

Assessing anxiety symptoms in children: Agreement between parents and children

Assessment of anxiety disorders in children is a difficult process and requires the use of multiple resources of information. Such resources may come from children, parents, and educators and they also require the use of multiple types of diagnostic tools, like structured and semi-structured clinical interviews, as well as self-report questionnaires. Previous research shows that anxiety symptoms ratings of different informants are to some degree correlated (low to moderate agreement) but nonetheless also often show clear discrepancies. Important variables may affect the degree of child-parent agreement. The present study focused on child's gender and age possible impact. The aim of the present study was to examine the agreement between children's and parents' reports on self-reported questionnaires for anxiety symptoms. 431 children from 4th to 6th grade of elementary school and their parents participated in the study. 190 were boys and 241 were girls. Both children and their parents responded to Spence Children's Anxiety Scale (SCAS) (child's and parent's version correspondingly). Relations between children's and parents' reports concerning anxiety symptoms were examined by calculation Pearson's correlation coefficients. The results showed that there was a medium but statistically important positive correlation between children's and parents' reports on SCAS total score (r=0.50, p<0.01). Concerning SCAS subscales results supported that higher correlations were those reported for Separation Anxiety (r=0.53, p<0.01) and Fear of Physical Injury (r=0.55, p<0.01). Concerning gender differences the present study found that correlation coefficients for girls were higher than for boys in SCAS total score (r=0.57 and r=0.39 correspondingly, p<0.01). Correlations according to age showed that the highest correlation coefficients were found in comparatively older children (r=0.34, r=0.54 και r=0.63, p<0.01 for 4th, 5th and 6th Grade). The latter underlies that in the process of assessing and diagnosing anxiety disorders in children, it is both necessary and important to gather information from multiple sources, especially in cases of younger children.

[A study of the effectiveness of a group-based cognitive-behavioral parent training program]

The role of the family in the development of the child as well as the quality of the parent-child relationship and its effect in the social, mental and cognitive development of the child has been the focus of attention of many sciences and scientists and it has been discovered that many parents are not well prepared to do their best for their children. The parent training programmes are willing to partly give a solution to this with their preventive role. In recent years, the effectiveness of the parent training programmes, which are offered to "high risk" parents, has been the focus of a big amount of research, meta-analyses and reviews. A smaller amount concerns the effectiveness of the universal programmes which are offered to the parents of the general population. The effectiveness of a ten-meeting structured group parent training programme of cognitive-behavioral approach, which had been offered to mothers of the general population, was researched in the present study. It aimed to research the effectiveness of the specific programme in the children's behavior and the subjective perception of the functionality of the family of the mothers who chose to participate in and completed the programme (n=56, experimental group/participants), compared to those who chose not to (n=113, control group/non participants). The mothers of the two groups were mothers with children aged between 2 and 12 and filled in the Family Adaptation and Cohesion Scales, FACES-III and the Questionnaire of Inter-personal and Cross-personal Adaptation, before (Phases A) and after (Phases B) the programme. The two groups were fully matched and did not present any significant difference regarding their demographic characteristics. During both Phases A and B of the training programme participants and non-participants expressed a high degree of satisfaction by the functionality of their family and did not differentiate significantly in the evaluation of the existent family cohesion and adaptability, the type of the family based on the cohesion and adaptability and the general type of family based on the functionality. In addition, while the children of the participants were, before the start of the programme, in a significantly disadvantaged position compared to the children of the non-participants, after the end of the programme, they were significantly improved, decreasing the negative symptoms and behaviors. This particular parent training programme of cognitive-behavioral approach, as well as other programmes which belong to the same theoretical direction, could contribute to the prevention of the behavior problems and the promotion of the mental health.

Hypoxia inducible factor-1 alpha and vascular endothelial growth factor in biopsies of small cell lung carcinoma

Neoangiogenesis has been documented in small cell lung carcinoma (SCLC). In addition, antiangiogenic therapies are being tested in clinical trials that involve SCLC. However, study of the underlying mechanisms has been performed almost exclusively in cell lines. In the current study, we immunostained 30 biopsy samples of SCLC with antibodies to hypoxia inducible factor-1 alpha (HIF-1 alpha), vascular endothelial growth factor (VEGF), vascular endothelial growth factor-receptor 1 (VEGF-R1/flt-1) and vascular endothelial growth factor-receptor 2 (VEGF-R1/flk-1). The immunoreactivity was analyzed using a bivariate Spearman correlation test and linear regression analysis. We found significant correlation between HIF-1 alpha nuclear staining and VEGF staining. Moreover HIF-1 alpha+/VEGF+ cases were associated with poor survival. We also found a positive correlation between VEGF and VEGF-R2 expression. We suggest that a HIF-1 alpha/VEGF angiogenic pathway may exist in vivo in SCLC, similar to that in non-SCLC. Our data also suggest a potential VEGF/VEGFR-2 autocrine pathway in SCLC. The inclusion of novel inhibitors to HIF-1 alpha and other factors may optimize antiangiogenic interventions in SCLC.

Enzyme-linked immunosorbent assay for pharmacological studies targeting hypoxia-inducible factor 1alpha

Hypoxia-inducible factor 1 (HIF-1) activates the transcription of a wide range of genes related to oxygen delivery and metabolic adaptation under hypoxic (low-oxygen) conditions. HIF-1 is, in fact, a heterodimer of two subunits, HIF-1alpha and HIF-1beta. The only analytical methods available for measuring HIF-1alpha levels in tumors are immunohistochemistry and Western blotting. Immunohistochemistry has the advantage of allowing the identification and direct examination of HIF-1alpha-expressing cells, but has the intrinsic limitation, as for Western blotting, of being nonquantitative. We developed and validated an enzyme-linked immunosorbent assay (ELISA) approach to measure HIF-1alpha levels in cultured tumor cell lines in vitro. HIF-1alpha was expressed in thirteen tumor cell lines grown under hypoxic conditions; however, the levels differed strongly between cell lines. These data point to intrinsic differences between cell lines for the induction of HIF-1alpha under hypoxic conditions. The ELISA developed in the present study is thus an interesting alternative to other analytical methods used to measure HIF-1alpha protein levels and should be useful in preclinical pharmacological studies targeting HIF-1alpha.

Pus1p-dependent tRNA pseudouridinylation becomes essential when tRNA biogenesis is compromised in yeast

Yeast Pus1p catalyzes the formation of pseudouridine (psi) at specific sites of several tRNAs, but its function is not essential for cell viability. We show here that Pus1p becomes essential when another tRNA:pseudouridine synthase, Pus4p, or the essential minor tRNA for glutamine are mutated. Strikingly, this mutant tRNA, which carries a mismatch in the T psi C arm, displays a nuclear export defect. Furthermore, nuclear export of at least one wild-type tRNA species becomes defective in the absence of Pus1p. Our data, thus, show that the modifications formed by Pus1p are essential when other aspects of tRNA biogenesis or function are compromised and suggest that impairment of nuclear tRNA export in the absence of Pus1p might contribute to this phenotype.

Arc1p organizes the yeast aminoacyl-tRNA synthetase complex and stabilizes its interaction with the cognate tRNAs

Eukaryotic aminoacyl-tRNA synthetases, in contrast to their prokaryotic counterparts, are often part of high molecular weight complexes. In yeast, two enzymes, the methionyl- and glutamyl-tRNA synthetases associate in vivo with the tRNA-binding protein Arc1p. To study the assembly and function of this complex, we have reconstituted it in vitro from individually purified recombinant proteins. Our results show that Arc1p can readily bind to either or both of the two enzymes, mediating the formation of the respective binary or ternary complexes. Under competition conditions, Arc1p alone exhibits broad specificity and interacts with a defined set of tRNA species. Nevertheless, the in vitro reconstituted Arc1p-containing enzyme complexes can bind only to their cognate tRNAs and tighter than the corresponding monomeric enzymes. These results demonstrate that the organization of aminoacyl-tRNA synthetases with general tRNA-binding proteins into multimeric complexes can stimulate their catalytic efficiency and, therefore, offer a significant advantage to the eukaryotic cell.

Cloning and characterization of the Schizosaccharomyces pombe tRNA:pseudouridine synthase Pus1p

Saccharomyces cerevisiae cells that carry deletions in both the LOS1 (a tRNA export receptor) and the PUS1 (a tRNA:pseudouridine synthase) genes exhibit a thermosensitive growth defect. A Schizosaccharomyces pombe gene, named spPUS1, was cloned from a cDNA library by complementation of this conditional lethal phenotype. The corresponding protein, spPus1p, shows sequence similarity to S. cerevisiae and murine Pus1p as well as other known members of the pseudouridine synthase family. Accordingly, recombinant spPus1p can catalyze in vitro the formation of pseudouridines at positions 27, 28, 34, 35 and 36 of yeast tRNA transcripts. The sequence and functional conservation of the Pus1p proteins in fungi and mammalian species and their notable absence from prokaryotes suggest that this family of pseudouridine synthases is required for a eukaryote-specific step of tRNA biogenesis, such as nuclear export.

Assessment of dysfunctional working models of self and others in schizophrenic patients: a summary of data collected in nine nations. International Research Group

OBJECTIVE

To investigate the cross-cultural feasibility of a new scale for assessing dysfunctional working models of self and others, and to evaluate its discriminative power.

METHOD

Schizophrenic patients (N=351), non-psychotic patients (N= 86) and non-clinical subjects (N= 511) collected in 10 centres completed the DWM-S. Current psychopathology was assessed by means of the BPRS.

RESULTS

Alpha coefficients were high in all samples. Mean scores on the DWM-S appeared to be comparable in all countries, suggesting cross-national generalizability. No significant correlation was found with sex, age, levels of psychopathology and duration of illness. Discriminant analyses showed that more than 70% of the schizophrenic patients are correctly classified.

CONCLUSION

The DWM-S is an easily administered self-report instrument which allows to pinpoint internal dysfunctional working models of self and others in various types of patients. It is a useful tool for case conceptualization, especially when psychotherapeutic interventions are part of the treatment programme.

Review: transport of tRNA out of the nucleus-direct channeling to the ribosome?

Although tRNA was the first substrate whose export from the nuclei of eukaryotic cells had been shown to be carrier-mediated and active, it has only been in the last 2 years that the first mechanistic details of this nucleocytoplasmic transport pathway have begun to emerge. A member of the importin/karyopherin beta superfamily, Los1p in yeast and Xpo-t in vertebrates, has been shown to export tRNA in cooperation with the small GTPase Ran (Gsp1p) from the nucleus into the cytoplasm, where tRNA becomes available for translation. However, Los1p is not essential for viability in yeast cells, suggesting that alternative tRNA export pathways exist. Recent results show that aminoacylation and a translation factor are also required for efficient nuclear tRNA export. Thus, protein translation and nuclear export of tRNA appear to be coupled processes.

An aminoacylation-dependent nuclear tRNA export pathway in yeast

Yeast Los1p, the homolog of human exportin-t, mediates nuclear export of tRNA. Using fluorescence in situ hybridization, we could show that the export of some intronless tRNA species is not detectably affected by the disruption of LOS1. To find other factors that facilitate tRNA export, we performed a suppressor screen of a synthetically lethal los1 mutant and identified the essential translation elongation factor eEF-1A. Mutations in eEF-1A impaired nuclear export of all tRNAs tested, which included both spliced and intronless species. An even stronger defect in nuclear exit of tRNA was observed under conditions that inhibited tRNA aminoacylation. In all cases, inhibition of tRNA export led to nucleolar accumulation of mature tRNAs. Our data show that tRNA aminoacylation and eEF-1A are required for efficient nuclear tRNA export in yeast and suggest coordination between the protein translation and the nuclear tRNA processing and transport machineries.

Transfer RNA biogenesis: A visa to leave the nucleus

Only correctly folded and mature tRNAs can leave the nucleus and enter the cytoplasm. Surprisingly, tRNA-aminoacylation has been found to occur, not only in the cytosol, but also inside the nucleus, where it may act as an additional proofreading step and facilitate the export of 'ready-to-function' aminoacyl-tRNAs.

A novel in vivo assay reveals inhibition of ribosomal nuclear export in ran-cycle and nucleoporin mutants

To identify components involved in the nuclear export of ribosomes in yeast, we developed an in vivo assay exploiting a green fluorescent protein (GFP)-tagged version of ribosomal protein L25. After its import into the nucleolus, L25-GFP assembles with 60S ribosomal subunits that are subsequently exported into the cytoplasm. In wild-type cells, GFP-labeled ribosomes are only detected by fluorescence in the cytoplasm. However, thermosensitive rna1-1 (Ran-GAP), prp20-1 (Ran-GEF), and nucleoporin nup49 and nsp1 mutants are impaired in ribosomal export as revealed by nuclear accumulation of L25-GFP. Furthermore, overexpression of dominant-negative RanGTP (Gsp1-G21V) and the tRNA exportin Los1p inhibits ribosomal export. The pattern of subnuclear accumulation of L25-GFP observed in different mutants is not identical, suggesting that transport can be blocked at different steps. Thus, nuclear export of ribosomes requires the nuclear/cytoplasmic Ran-cycle and distinct nucleoporins. This assay can be used to identify soluble transport factors required for nuclear exit of ribosomes.

Yeast Los1p has properties of an exportin-like nucleocytoplasmic transport factor for tRNA

Saccharomyces cerevisiae Los1p, which is genetically linked to the nuclear pore protein Nsp1p and several tRNA biogenesis factors, was recently grouped into the family of importin/karyopherin-beta-like proteins on the basis of its sequence similarity. In a two-hybrid screen, we identified Nup2p as a nucleoporin interacting with Los1p. Subsequent purification of Los1p from yeast demonstrates its physical association not only with Nup2p but also with Nsp1p. By the use of the Gsp1p-G21V mutant, Los1p was shown to preferentially bind to the GTP-bound form of yeast Ran. Furthermore, overexpression of full-length or N-terminally truncated Los1p was shown to have dominant-negative effects on cell growth and different nuclear export pathways. Finally, Los1p could interact with Gsp1p-GTP, but only in the presence of tRNA, as revealed in an indirect in vitro binding assay. These data confirm the homology between Los1p and the recently identified human exportin for tRNA and reinforce the possibility of a role for Los1p in nuclear export of tRNA in yeast.

Nuclear mRNA export requires complex formation between Mex67p and Mtr2p at the nuclear pores

We have identified between Mex67p and Mtr2p a complex which is essential for mRNA export. This complex, either isolated from yeast or assembled in Escherichia coli, can bind in vitro to RNA through Mex67p. In vivo, Mex67p requires Mtr2p for association with the nuclear pores, which can be abolished by mutating either MEX67 or MTR2. In all cases, detachment of Mex67p from the pores into the cytoplasm correlates with a strong inhibition of mRNA export. At the nuclear pores, Nup85p represents one of the targets with which the Mex67p-Mtr2p complex interacts. Thus, Mex67p and Mtr2p constitute a novel mRNA export complex which can bind to RNA via Mex67p and which interacts with nuclear pores via Mtr2p.

Mtr10p functions as a nuclear import receptor for the mRNA-binding protein Npl3p

MTR10, previously shown to be involved in mRNA export, was found in a synthetic lethal relationship with nucleoporin NUP85. Green fluorescent protein (GFP)-tagged Mtr10p localizes preferentially inside the nucleus, but a nuclear pore and cytoplasmic distribution is also evident. Purified Mtr10p forms a complex with Npl3p, an RNA-binding protein that shuttles in and out of the nucleus. In mtr10 mutants, nuclear uptake of Npl3p is strongly impaired at the restrictive temperature, while import of a classic nuclear localization signal (NLS)-containing protein is not. Accordingly, the NLS within Npl3p is extended and consists of the RGG box plus a short and non-repetitive C-terminal tail. Mtr10p interacts in vitro with Gsp1p-GTP, but with low affinity. Interestingly, Npl3p dissociates from Mtr10p only by incubation with Ran-GTP plus RNA. This suggests that Npl3p follows a distinct nuclear import pathway and that intranuclear release from its specific import receptor Mtr10p requires the cooperative action of both Ran-GTP and newly synthesized mRNA.

Characterization of yeast protein Deg1 as pseudouridine synthase (Pus3) catalyzing the formation of psi 38 and psi 39 in tRNA anticodon loop

The enzymatic activity of yeast gene product Deg1 was identified using both disrupted yeast strain and cloned recombinant protein expressed in yeast and in Escherichia coli. The results show that the DEG1-disrupted yeast strain lacks synthase activity for the formation of pseudouridines psi 38 and psi 39 in tRNA whereas the other activities, specific for psi formation at positions 13, 27, 28, 32, 34, 35, 36, and 55 in tRNA, remain unaffected. Also, the His6-tagged recombinant yeast Deg1p expressed in E. coli as well as a protein fusion with protein A in yeast display the enzymatic activity only toward psi 38 and psi 39 formation in different tRNA substrates. Therefore, Deg1p is the third tRNA:pseudouridine synthase (Pus3p) characterized so far in yeast. Disruption of the DEG1 gene is not lethal but reduces considerably the yeast growth rate, especially at an elevated temperature (37 degrees C). Deg1p localizes both in the nucleus and in the cytoplasm, as shown by immunofluorescence microscopy. Identification of the pseudouridine residues present (or absent) in selected naturally occurring cytoplasmic and mitochondrial tRNAs from DEG1-disrupted strain points out a common origin of psi 38- and psi 39-synthesizing activity in both of these two cellular compartments. The sensitivity of Pus3p (Deg1p) activity to overall three-dimensional tRNA architecture and to a few individual mutations in tRNA was also studied. The results indicate the existence of subtle differences in the tRNA recognition by yeast Pus3p and by its homologous tRNA:pseudouridine synthase truA from E. coli (initially called hisT or PSU-I gene product).

A conserved domain within Arc1p delivers tRNA to aminoacyl-tRNA synthetases

Two yeast enzymes that catalyze aminoacylation of tRNAs, MetRS and GluRS, form a complex with the protein Arc1p. We show here that association of Arc1p with MetRS and GluRS is required in vivo for effective recruitment of the corresponding cognate tRNAs within this complex. Arc1p is linked to MetRS and GluRS through its amino-terminal domain, while its middle and carboxy-terminal parts comprise a novel tRNA-binding domain. This results in high affinity binding of cognate tRNAs and increased aminoacylation efficiency. These findings suggest that Arc1p operates as a mobile, trans-acting tRNA-binding synthetase domain and provide new insight into the role of eukaryotic multimeric synthetase complexes.

Intron-dependent enzymatic formation of modified nucleosides in eukaryotic tRNAs: a review

In eukaryotic cells, especially in yeast, several genes encoding tRNAs contain introns. These are removed from pre-tRNAs during the maturation process by a tRNA-specific splicing machinery that is located within the nucleus at the nuclear envelope. Before and after the intron removal, several nucleoside modifications are added in a stepwise manner, but most of them are introduced prior to intron removal. Some of these early nucleoside modifications are catalyzed by intron-dependent enzymes while most of the others are catalyzed in an intron-independent manner. In the present paper, we review all known cases where the nucleoside modifications were shown to depend strictly on the presence of an intron. These are pseudouridines at anticodon positions 34, 35 and 36 and 5-methylcytosine at position 34 of several eukaryotic tRNAs. One common property of the corresponding intron-dependent modifying enzymes is that their activities are essentially dependent on the local specific architecture of the pre-tRNA molecule that comprises the anticodon stem and loop prolonged by the intron domain. Thus introns clearly serve as internal (cis-type) RNAs that guide nucleoside modifications by providing transient target sites in tRNA for selected nuclear modifying enzymes. This situation may be similar to the recently discovered (trans-type) snoRNA-guided process of ribose methylations of ribosomal RNAs within the nucleolus of eukaryotic cells.

Mitotic phosphorylation of the lamin B receptor by a serine/arginine kinase and p34(cdc2)

The lamin B receptor (LBR) is an integral protein of the inner nuclear membrane that is modified at interphase by a nuclear envelope-bound protein kinase. This enzyme (RS kinase) specifically phosphorylates arginine-serine dipeptide motifs located at the NH2-terminal domain of LBR and regulates its interactions with other nuclear envelope proteins. To compare the phosphorylation state of LBR during interphase and mitosis, we performed phosphopeptide mapping of in vitro and in vivo 32P-labeled LBR and analyzed a series of recombinant proteins and synthetic peptides. Our results show that LBR undergoes two types of mitotic phosphorylation mediated by the RS and the p34(cdc2) protein kinases, respectively. The RS kinase modifies similar sites at interphase and mitosis (i.e. Ser76, Ser78, Ser80, Ser82, Ser84), whereas p34(cdc2) mainly phosphorylates Ser71. These findings clarify the phosphorylation state of LBR during the cell cycle and provide new information for understanding the mechanisms responsible for nuclear envelope assembly and disassembly.

The lamin B receptor (LBR) provides essential chromatin docking sites at the nuclear envelope

Morphological studies have established that peripheral heterochromatin is closely associated with the nuclear envelope. The tight coupling of the two structures has been attributed to nuclear lamins and lamin-associated proteins; however, it remains to be determined which of these elements are essential and which play an auxiliary role in nuclear envelope-chromatin interactions. To address this question, we have used as a model system in vitro reconstituted vesicles assembled from octyl glucoside-solubilized nuclear envelopes. Comparing the chromosome binding properties of normal, immunodepleted and chemically extracted vesicles, we have arrived at the conclusion that the principal chromatin anchorage site at the nuclear envelope is the lamin B receptor (LBR), a ubiquitous integral protein of the inner nuclear membrane. Consistent with this interpretation, purified LBR binds directly to chromatin fragments and decorates the surface of chromosomes in a distinctive banding pattern.

The yeast protein Arc1p binds to tRNA and functions as a cofactor for the methionyl- and glutamyl-tRNA synthetases

Arc1p was found in a screen for components that interact genetically with Los1p, a nuclear pore-associated yeast protein involved in tRNA biogenesis. Arc1p is associated with two proteins which were identified as methionyl-tRNA and glutamyl-tRNA synthetase (MetRS and GluRS) by a new mass spectrometry method. ARC1 gene disruption leads to slow growth and reduced MetRS activity, and synthetically lethal arc1- mutants are complemented by the genes for MetRS and GluRS. Recombinant Arc1p binds in vitro to purified monomeric yeast MetRS, but not to an N-terminal truncated form, and strongly increases its apparent affinity for tRNAMet. Furthermore, Arc1p, which is allelic to the quadruplex nucleic acid binding protein G4p1, exhibits specific binding to tRNA as determined by gel retardation and UV-cross-linking. Arc1p is, therefore, a yeast protein with dual specificity: it associates with tRNA and aminoacyl-tRNA synthetases. This functional interaction may be required for efficient aminoacylation in vivo.

Characterization of p18, a component of the lamin B receptor complex and a new integral membrane protein of the avian erythrocyte nuclear envelope

Employing avian erythrocytes, we have previously isolated a multimeric complex consisting of the lamin B receptor (LBR, or p58), the nuclear lamins, an LBR-specific kinase, a 34-kDa protein, and an 18-kDa polypeptide termed p18. As the LBR kinase and the 34-kDa component have been recently characterized, we now proceed in the characterization of p18. We show here that p18 is an integral membrane protein specific to the erythrocyte nuclear envelope which binds to LBR and B-type lamins. NH2-terminal sequencing indicates that p18 is distinct from other nuclear envelope components, but has similarity to the mitochondrial isoquinoline-binding protein. In situ analysis by immunoelectron microscopy and examination of digitonin-permeabilized cells by indirect immunofluorescence show that p18, unlike LBR and other lamin-binding proteins, is equally distributed between the inner and outer nuclear membrane. Furthermore, cycloheximide inhibition experiments reveal that the fraction of p18 that resides in the outer nuclear membrane does not represent nascent chains en route to the inner nuclear membrane, but rather material in equilibrium with the p18 that partitions with the inner nuclear membrane. The paradigm of p18 suggests that transmembrane complexes formed by the nuclear lamins and LBR provide potential docking sites for integral membrane proteins of the nuclear envelope that equilibrate between the rough endoplasmic reticulum and the inner nuclear membrane.

Nuclear pore proteins are involved in the biogenesis of functional tRNA

Los1p and Pus1p, which are involved in tRNA biogenesis, were found in a genetic screen for components interacting with the nuclear pore protein Nsp1p. LOS1, PUS1 and NSP1 interact functionally, since the combination of mutations in the three genes causes synthetic lethality. Pus1p is an intranuclear protein which exhibits a nucleotide-specific and intron-dependent tRNA pseudouridine synthase activity. Los1p was shown previously to be required for efficient pre-tRNA splicing; we report here that Los1p localizes to the nuclear pores and is linked functionally to several components of the tRNA biogenesis machinery including Pus1p and Tfc4p. When the formation of functional tRNA was analyzed by an in vivo assay, the los1(-) pus1(-) double mutant, as well as several thermosensitive nucleoporin mutants including nsp1, nup116, nup133 and nup85, exhibited loss of suppressor tRNA activity even at permissive temperatures. These data suggest that nuclear pore proteins are required for the biogenesis of functional tRNA.

A nuclear envelope-associated kinase phosphorylates arginine-serine motifs and modulates interactions between the lamin B receptor and other nuclear proteins

Previous studies have identified a subassembly of nuclear envelope proteins, termed "the LBR complex." This complex includes the lamin B receptor protein (LBR or p58), a kinase which phosphorylates LBR in a constitutive fashion (LBR kinase), the nuclear lamins A and B, an 18-kDa polypeptide (p18), and a 34-kDa protein (p34/p32). The latter polypeptide has been shown to interact with the HIV-1 proteins Rev and Tat and with the splicing factor 2 (SF2). Using recombinant proteins produced in bacteria and synthetic peptides representing different regions of LBR, we now show that the LBR kinase modifies specifically arginine-serine (RS) dipeptide motifs located at the nucleoplasmic, NH2-terminal domain of LBR and in members of the SR family of splicing factors. Furthermore, we show that the NH2-terminal domain of LBR binds to p34/p32, whereas a mutated domain lacking the RS region does not. Phosphorylation of LBR by the RS kinase completely abolishes binding of p34/p32, suggesting that this enzyme regulates interactions among the components of the LBR complex.

Nucleocytoplasmic transport: factors and mechanisms

In the past two years, our knowledge concerning the mechanisms of nucleocytoplasmic transport through the nuclear pore complex (NPC) has considerably expanded. The application of in vitro systems that reconstitute nuclear protein import has allowed the identification of cytosolic factors that are required for the import process. Microinjection into Xenopus oocytes and yeast genetic systems have provided interesting candidates for RNA export mediators. Functional and structural analysis of nucleoporins has demonstrated the involvement of NPC components in the transport process. Finally, new concepts have emerged such as the integration of the mechanisms of the nuclear protein import and RNA export reactions and the assembly of the transport machinery at specialised domains of the NPC.

The lamin B receptor-associated protein p34 shares sequence homology and antigenic determinants with the splicing factor 2-associated protein p32

The lamin B receptor (p58) is an inner nuclear membrane protein that forms an in vivo complex with the nuclear lamins, a nuclear envelope kinase, and two other nuclear proteins with apparent M(r) of 18,000 (p18) and 34,000 (p34). We now report the isolation of p34 by partial dissociation of the immunoaffinity-purified p58 protein complex. Determination of the N-terminal amino acid sequence of purified p34 shows that this polypeptide is homologous to p32, a splicing factor 2 (SF2)-associated protein. The relatedness between p34 and p32 can be further established by showing that antibodies raised against N- and C-terminal peptides of p32 cross-react with purified p34. As the amino acid sequence of p58 contains an arginine/serine (RS)-rich region similar to the RS-rich region found in SF 2, we speculate that these domains provide binding sites for p34 and that this protein may be a linker between the nuclear membrane and intranuclear spliceosomal substructures.

Lamins and lamin-associated proteins

A variety of morphological and biochemical studies have established that the nuclear lamins play an important role in nuclear structure and dynamics. Recent work reveals the existence of specialized lamin isotypes and novel pathways of modulation of lamin import into the nucleus via phosphorylation by protein kinase C. Other studies also unveil a wide spectrum of molecular interactions between the lamin proteins and integral membrane components of the nuclear envelope.

Barley beta-glucosidase: expression during seed germination and maturation and partial amino acid sequences

Unlike most of the hydrolytic enzymes that participate in endosperm mobilization, beta-glucosidase of barley (Hordeum vulgare) seeds does not increase during germination, even in the presence of exogenously added gibberellic acid. However, the germination process affects the physical properties of beta-glucosidase in terms of charge and apparent molecular weight. Analysis of developing barley grains shows that the enzyme is synthesized two weeks before maturation and is stored in the endosperm of the dry dormant seed. Partial amino acid sequencing of the purified beta-glucosidase demonstrates significant similarity between the barley enzyme and beta-glycosidases that belong to family 1 of glycosyl hydrolases.

The inner nuclear membrane protein p58 associates in vivo with a p58 kinase and the nuclear lamins

p58, also referred to as the lamin B receptor, is an intrinsic protein of the inner nuclear membrane that binds in vitro to lamin B. Previous studies have demonstrated that p58 is phosphorylated in vivo and removal of its phosphate moieties affects lamin B binding. Using affinity-purified antipeptide antibodies, we have now immunoisolated p58 from bird erythrocyte lysates under isotonic, non-denaturing conditions. Analysis of the immunopurified material shows that five distinct proteins are tightly and specifically associated with p58. Two of these polypeptides can be identified as nuclear lamins A and B. The immunoisolate also contains a kinase activity that phosphorylates p58 in vivo and in vitro, exclusively at serine residues, as indicated by phosphoamino acid analysis and two-dimensional phosphopeptide mapping. Cell fractionation experiments and in vitro phosphorylation assays demonstrate that the p58 kinase resides in the nuclear envelope and is distinct from protein kinase A and cdc2 kinase, for both of which p58 is an in vitro substrate. These data suggest that p58 is interacting in vivo with a p58 kinase and the nuclear lamins.

Binding of lamin A to polynucleosomes

Morphological observations suggest a close association between heterochromatin and the nuclear lamina. To investigate the molecular aspects of this association, we have established a simple sedimentation assay employing purified lamin proteins, or their 125I-labeled derivatives, and polynucleosomal particles isolated from avian erythrocytes. We report here that purified, unlabeled lamin A and 125I-lamin A, but not 125I-lamin B or 125I-bovine serum albumin, bind to polynucleosomes in a saturable and specific fashion. The specific binding of 125I-lamin A is of high affinity (Kd = approximately 1 x 10(-9) M) and is distinctly temperature-dependent. This interaction is not affected by exogenous polyionic agents such as polylysine and DNA, but it can be abolished by protease digestion of the polynucleosomes. These data suggest that nuclear lamin A maintains a direct association with a proteinaceous constituent of interphase chromatin.

Lactose-hydrolyzing beta-glycosidases of barley meal

A beta-glucosidase and a beta-galactosidase were purified to homogeneity from barley meal. The beta-glucosidase is a single basic polypeptide (pI greater than 8.5) with an Mr of 53,000 acting optimally at pH 4.5-5.0. The beta-galactosidase is composed of two subunits with an Mr of 42,000 and 33,000, respectively, and is acidic in nature (pI less than 5.7). Both enzymes are able to hydrolyze lactose with Michaelis constants lower than the concentration of this sugar in milk whey. Consequently, barley seems to be an inexpensive source of lactose-splitting enzymes.