Inhibition of DLX-7 homeobox gene causes decreased expression of GATA-1 and c-myc genes and apoptosis

The DLX gene family is a family of divergent homeobox genes which are related to the Drosophila distal-less (Dll) gene and has been reported to be expressed primarily in the forebrain and craniofacial structures. We have previously identified a new member of this family, DLX-7. We now report that this gene is expressed in normal hematopoietic cells and leukemia cell lines with erythroid characteristics. We used an antisense oligonucleotide targeted against the translation start site of DLX-7 mRNA to inhibit its expression in a human erythroleukemia cell line K562, which expresses DLX-7 at a high level. The antisense oligonucleotide efficiently reduced the DLX-7 mRNA, while control oligonucleotides, including a mutant oligonucleotide identical to the antisense sequence except for four nucleotide mismatches, had no effect on DLX-7 mRNA level. Inhibition of DLX-7 expression decreased the plating efficiency by approximately 70% compared with control. The antisense treatment caused apoptosis, as shown by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-digoxigenin nick end labeling (TUNEL) method. Down-regulation of DLX-7 expression by antisense treatment was associated with a reduction in GATA-1 and c-myc mRNA levels. Thus, we conclude that DLX-7 is expressed in hematopoietic cells and that the inhibition of its expression results in the decreased levels of GATA-1 and c-myc genes, with an accompanying induction of apoptosis.

[Breakage of a Seldinger spring guide wire during percutaneous catheterization of a subclavian vein]

Spring guide wires have been widely used for the central venous catheterization with the popularity of the Seldinger technique. We report here an accidental breakage of a spring guide wire during percutaneous catheterization of a subclavian vein. The venipuncture by a plastic catheter over an introducer needle and the insertion of a spring guide wire through the catheter were easily achieved. However, the insertion of an indwelling catheter over the guide wire was difficult to perform, and the pulling out of the guide wire from the catheter was more difficult, which brought the uncoiling of the spring part of the guide wire from the mandrel. The tip of the guide wire was not cut off, and there were no sequelae in the patient. A plastic catheter over an introducer needle for a subclavian venipuncture is so flexible that it is occasionally bent between the clavicle and the first rib after pulling out of the inside needle. Probably, that is the reason of the difficulties of the insertion of an indwelling catheter and the pulling out of a guide wire. The use of a rigid metal needle for the venipuncture is an alternative way to avoid these troubles.

Primary structure and properties of the Na+/glucose symporter (Sg1S) of Vibrio parahaemolyticus

Previously, we cloned and sequenced a DNA fragment from Vibrio parahaemolyticus and found four open reading frames (ORFs). Here, we clearly demonstrate that one of the ORFs, ORF1, is the gene (sglS) encoding a Na+/glucose symporter (SglS). We characterize the Na+/glucose symporter produced in Escherichia coli mutant (JM1100) cells which lack original glucose transport activity and galactose transport activity. We also show that phlorizin, a potent inhibitor of the SGLT1 Na+/glucose symporter of animal cells, inhibited glucose transport, but not galactose transport, via the SglS system.

Passive smoking and plasma fibrinogen concentrations

To examine the effect of passive smoking on plasma fibrinogen, a coronary risk factor, a cross-sectional study was conducted between 1990 and 1993 for 1,780 Japanese women aged 45-74 years who resided in Kyowa town, Ibaraki-ken, Japan. Fibrinogen concentrations controlling for age, body mass index, ethanol intake, serum total cholesterol, diabetes mellitus, and menopausal status were 8.6 (95% confidence interval 1.6-15.6) mg/dl higher in women exposed passively to smoking outside the home (n = 435) and 11.2 (95% confidence interval 3.0-19.3) mg/dl higher in women exposed both in and outside the home (n = 272) than in women unexposed in either location (n = 524). These effects of passive smoking were about 40-60% of that of current active smoking. An effect of passive smoking at home only was small and not statistically significant. The association between fibrinogen and passive smoking was primarily observed in women aged 45-59 years but not in those aged 60-74 years. Passive smoking may raise the risk of coronary heart disease partly by increasing plasma fibrinogen concentrations.

Pattern of expression and their clinical implications of the GATA family, stem cell leukemia gene, and EVI1 in leukemia and myelodysplastic syndromes

Transcription factors play a key role in controlling the cellular differentiation of hematopoietic cells. Among the known transcription factors, both GATA-1 and SCL play roles in the cellular differentiation of erythrocytic and megakaryocytic lineages, while GATA-2 is thought to maintain and promote the proliferation of early hematopoietic progenitors. In this review, the clinical implications of expression of the GATA family, SCL, and EVI1 gene in various types of human leukemia are discussed. De novo acute myeloid leukemia (AML) patients may be subdivided into three categories depending on the expression pattern of transcription factors, i.e., GATA-1(+)SCL(+), GATA-1(+)SCL(-), and GATA-1(-)SCL(-). AML patients with both GATA-1 and SCL expression have a poor prognosis and have some characteristic clinical and hematologic features. The EVI1 gene may be expressed through at least two pathways in hematologic malignancies; one is related to chromosomal changes at 3q26, while the other is related to myelodysplasia regardless of chromosomal changes at 3q26 region. These findings suggest that the pattern of expression in transcription factors in abnormal hematopoietic cells is reflected in the malignant phenotype and play a role in the pathogenesis of the disease.

Polymorphism of the apolipoprotein B gene and blood lipid concentrations in Japanese and Caucasian population samples

To examine whether a racial difference in apolipoprotein B (Apo B) gene polymorphism between Japanese and American Caucasians corresponds with the lower blood cholesterol concentrations in Japanese than in Americans, we examined the EcoRI polymorphism of the Apo B gene for 271 nonsmoking men and women aged 47-69 years in two population-based samples: rural Japanese living in Akita and Caucasians living in Minneapolis-St. Paul, Minnesota, USA. Mean values of serum cholesterol concentrations were significantly lower in Japanese than in Caucasians for both men and women (difference = 25-26 mg/dl). An allele-specific polymerase chain reaction was conducted to examine the Eco RI cutting site at the 12669 cDNA position of the Apo B gene. The allele R2 (absence of the cutting site) has been associated with lower cholesterol concentrations in two previous studies. The frequency of the R2 allele was 6% for Japanese and 17% for Caucasians (P < 0.001), and this race difference in allele frequency was identical for men and women. After controlling for age, body mass index, alcohol intake, and for women, menopausal status and hormone replacement therapy, the adjusted mean (SE) cholesterol level among Japanese was 204 (3) mg/dl for genotype R1R1 and 185 (7) mg/dl for genotype R1R2 or R2R2 combined (P = 0.01). The respective mean values among Caucasians were 224(5) mg/dl and 232(7) mg/dl (P = 0.36). The polymorphism had a similar effect on total cholesterol concentrations for both men and women. The observed lower prevalence of the R2 allele in Japanese than in Caucasians indicates that this variation in the Apo B gene does not explain the racial difference in blood cholesterol concentrations.

Mutational analysis of the CitA citrate transporter from Salmonella typhimurium: altered substrate specificity

The CitA citrate transporter in Salmonella typhimurium is encoded by the citA gene and consists of 434 amino acid residues that probably include 12 membrane-spanning segments [Shimamoto. T., et al. (1991) J. Biochem. 110, 22-28]. CitA mutants with altered substrate specificities were isolated by in vitro mutagenesis using nitrous acid. The mutants could grow on isocitrate as a sole carbon source which normally cannot be transported well by the CitA transporter of S. typhimurium. The mutation sites in the citA gene of the nine mutants were determined to involve single residues at seven sites (one mutation per mutant). The original amino acid residues at these sites (Arg-19, Ala-38, Glu-51, Gly-132, Ala-169, Pro-262 and Leu-271) were identified to be responsible for the altered substrate specificity. All these amino acid residues were conserved in four other homologous citrate transporters from Escherichia coli, Citrobacter amalonaticus and Klebsiella pneumoniae and are suggested to be involved in substrate recognition by the CitA transporter.

Replication errors in hematological neoplasias: genomic instability in progression of disease is different among different types of leukemia

Genetic alteration, including genomic instability, is an ultimate step toward the malignant process. One approach to delineating replication errors in cancer cells is to determine the alterations of microsatellites, which are short, repeated nucleotide sequences existing throughout the genomes. We used a fluorescent system to assess microsatellite changes in seven loci (D2S123, D3S643, D5S107, LPL, D17S261, TP53, and D18S34) of 73 consecutive patients with various hematological neoplasias. De novo acute leukemia patients had a low frequency (<1%) of microsatellite alterations at each locus, and none of them demonstrated multiple microsatellite changes. In chronic myeloid leukemia patients, no microsatellite instability was detected in the chronic phase, whereas a relatively high frequency (25%) of multiple microsatellite changes was evident in the blastic phase, and half of these patients had multiple microsatellite changes. About 50% of the patients with myelodysplastic syndrome (MDS) and post-MDS acute myeloid leukemia (post-MDS AML) had microsatellite alterations. We next compared microsatellite alterations in two different hematological phases (MDS and post-MDS AML phases); 5 of 11 patients with post-MDS AML had de novo appearance of microsatellite instability during disease progression. This indicates that genomic instability at multiple microsatellite loci could occur either before or after leukemic transformation in MDS patients. We concluded that genomic instability in chronic myeloid leukemia might be linked to blastic transformation in combination with cytogenetic changes. In contrast, MDS patients had replication errors as a relatively early genetic event as well as a late genetic event. These results suggest that the involvement of genomic instability in the progression of disease is different among various types of leukemia.

Epidemiology of cerebrovascular disease: stroke epidemic in Japan

Japan had the highest mortality from stroke among developed countries in 1960, but experienced rapid changes in diet and other lifestyles with economic growth between the 1960s and the 1980s, which provided an unique opportunity to observe a natural experiment of changes in risk factors and stroke. Blood pressure levels declined due to improvements of drug treatment for hypertension and to dietary improvements such as sodium reduction. An increase in mean values of ethanol intake and body mass index did not correspond with a decline of blood pressure levels. Serum total cholesterol increased with an increased intake of meat, egg, milk and dairy products. Age-adjusted mortality rate of stroke declined 70% between 1960 and 1990. The changes of diet, blood pressure levels and stroke were more evident in rural populations than in urban populations. Risk factors of stroke has been investigated prospectively, and hypertension was found to be the most important risk factor. A low blood cholesterol was associated with the increased risk of intracerebral hemorrhage, which has been confirmed in several Japanese populations, Japanese Americans and Caucasian Americans. Thus, a rise in serum cholesterol suggested to contribute in part to a decline in intracerebral hemorrhage. Risk factors for cerebral infarction include age, atrial fibrillation and hypertensive endorgan effects such as resting electrocardiogram and fundscopic examination. A community-based hypertension control program for stroke prevention has been evaluated; a larger decline in stroke incidence in the intervention community (69%) than in the reference community (49%, the difference: p < 0.001). Effective community programs stimulated the formation of the 1982 national act on health and medical care in which every municipal government is required to conduct health screenings and education for residents aged 40 and over to prevent cardiovascular diseases.

Lipoprotein(a) and its correlates in Japanese and U.S. population samples

To examine whether serum levels of lipoprotein(a) [Lp(a)], a potential coronary risk factor, are higher in Caucasian-Americans than in Japanese, a circumstance that would correspond to the higher mortality from coronary heart disease in the United States than in Japan, we analyzed serum Lp(a) levels in 300 nonsmoking men and women aged 47-69 years. Participants were drawn from two population-based samples: rural Japanese living in Akita and Caucasians living in Minneapolis-St. Paul, MN. Geometric mean and median serum Lp(a) concentrations were higher (P < 0.05) in Japanese than in Caucasians for both men (difference in geometric mean = 3.2 mg/dL) and women (difference = 5.3 mg/dL). There was however, no racial difference in the proportion of elevated Lp(a) concentrations (i.e., > or = 30 mg/dL) in either sex. Alcohol intake was inversely correlated with Lp(a) levels in Japanese men, who had a high average alcohol intake, but not in other sex and racial groups. Serum Lp(a) was nonsignificantly but consistently correlated with plasma fibrinogen and LDL-cholesterol for all sex and racial groups. With adjustment for alcohol intake, LDL-cholesterol, and plasma fibrinogen, the Japanese-Caucasian difference in geometric mean Lp(a) values was even larger for men and was not changed for women. Results of the present study do not support the hypothesis that racial differences in Lp(a) concentrations contribute to the higher mortality rate from coronary heart disease in the United States than in Japan.

Plasma fibrinogen and its correlates in urban Japanese men

BACKGROUND

The intention of the study was to examine determinants of plasma fibrinogen concentrations in Japanese men.

METHODS

A cross-sectional study was conducted in 1991 among 995 male employees aged 40-59 years in two urban companies.

RESULTS

The overall mean value (standard deviation) of plasma fibrinogen concentration was 257 (57) mg/dl. There was a strong dose-response relationship between cigarette smoking and plasma fibrinogen concentration. Plasma fibrinogen was positively associated with age and serum total cholesterol, and inversely associated with ethanol intake, dietary intake of sea foods such as squid, octopus or shrimp. Intake of other major protein and lipid resources such as meat, eggs and milk, or intake of vegetables was not related to plasma fibrinogen. An effect of dietary intake of sea foods on plasma fibrinogen was small but significant after controlling for the other covariates; an 80 g/week larger intake of sea foods was associated with a 3.9 mg/dl (95% confidence interval: 0.5, 7.3) lower fibrinogen concentration.

CONCLUSIONS

This study confirms the relation of known coronary risk factors to plasma fibrinogen in Japanese men, and suggests that dietary intake of sea foods affects plasma fibrinogen concentrations.

Community-based education classes for hypertension control. A 1.5-year randomized controlled trial

Community-based hypertension control is important for primary prevention of cardiovascular disease. In this study, untreated men and women aged 35 to 69 years were randomly assigned to an intervention (n=56) or control (n=55) group in a 1.5-year community-based education program. Subjects had no evidence of hypertensive end-organ defects and had screening blood pressures of 140 to 179 mm Hg systolic and/or 90 to 109 mm Hg diastolic, with no difference in mean blood pressure between groups (148 to 150 mm Hg for mean systolic and 83 to 84 mm Hg for mean diastolic pressures). The intervention group took four education classes in the first 6 months and four classes during the next year, and the control group took two classes. Health education focused on reduced dietary sodium and increased milk intake, brisk walking, and, if necessary, reduction of alcohol and sugar intakes. Antihypertensive medication was started less often in the intervention than in the control group at 1.5 years (9% versus 24%, P <.05). Mean systolic pressure was 5 to 6 mm Hg less in the intervention than in the control group at both 6 months and 1.5 years (P <.05), with or without inclusion of those subjects who began antihypertensive medication. Diastolic pressure and body mass index did not change significantly between groups. Urinary sodium excretion declined in the intervention but not in the control group (differences between groups: P=.04 at 6 months and P=.07 at 1.5 years). According to a behavioral questionnaire, sodium reduction and milk increase were greater in the intervention than the control group (sodium: P <.01 at 6 months and P=.08 at 1.5 years; milk: P <.001 at 6 months and P <.01 at 1.5 years). Mean ethanol intake was reduced in the intervention but not the control group (P=.04 at 1.5 years). This community-based hypertension control program was effective in reducing systolic pressure levels by nonpharmacological means during the first 6 months and maintaining the reduction for 1.5 years.

A possible correlation between interferon-stimulated gene expression and cytogenetic responses in chronic myelogenous leukemia patients treated with alpha-interferon

We studied the expression of the interferon-stimulated genes (ISGs), ISG-54 and 2',5'-oligoadenylate synthetase (2'-5' OAS), using the reverse transcription-polymerase chain reaction in 22 patients with chronic myelogenous leukemia (CML), who were treated with alpha-interferon (alpha-IFN). At the time of diagnosis, 7 patients (31.8%) showed no detectable expression of either gene, whereas 8 expressed both. The remaining 7 expressed neither ISG-54 nor 2'-5' OAS. After alpha-IFN treatment, 5 of the 7 CML patients who had not previously express ISGs expressed either ISG-54 or 2'5' OAS or both and 6 of the 7 who had previously expressed either ISG-54 or 2'-5' OAS expressed both. Three of the 7 (42.9%) CML patients who expressed both genes before and after alpha-IFN administration showed cytogenetic responses, as did 6 of the 11 (54.5%) in whom ISG expression was induced. In contrast, cytogenetic responses occurred in none of the patients in whom ISG expression was not induced. These results suggest that induction of ISG-54 and 2'-5' OAS expression by alpha-IFN may be an indicator of cytogenetic responses and, therefore, of value for monitoring CML patients.

[The relation of alcohol intake to constitutional and biochemical variables in Japanese populations]

To investigate associations of alcohol intake to constitutional and biochemical variables, cross-sectional studies of men aged 40-59 years from six geographical and occupational populations with varied lifestyles were conducted in the 1990's. Systolic and diastolic blood pressures, glutamic oxaloacetic transaminase, gamma glutamyl transpeptidase, HDL-cholesterol, and uric acid were linearly associated with alcohol intake in all six populations. Drinkers of 2+ drinks (46 g ethanol or more) per day showed higher levels of triglyceride, glutamic pyruvic transaminase than never-drinkers. In two urban occupational populations, men who mainly drank beer had higher uric acid levels; men mainly drinking sake had higher blood pressures and lower serum total cholesterol; men mainly drinking whiskey had higher obesity indices. These differences in constitutional and biochemical variables related to type of alcoholic beverage consumed may be due to differences in lifestyles such as diet and physical activity.

Mutational analysis of Era, an essential GTP-binding protein of Escherichia coli

Era is an essential GTP-binding protein of an unknown function in Escherichia coli. On the basis of its sequence similarities to other GTP-binding proteins such as E. coli EF-Tu, EF-G, IF2 and eukaryotic Ras proteins, it has been suggested that the Era function is activated by GTP binding, and that subsequent conversion of bound GTP to GDP by the intrinsic GTPase activity modulates its function. Two Era mutants, one dominant negative mutant (dE), which has a deletion mutation from Ala40 to Gly49, and the other non-functional mutant (T42A/T43A), which has two substitution mutations, Thr42 to Ala and Thr43 to Ala, were analyzed for their abilities of GTP-binding and GTPase activity. It was found that the dE mutant lost the GTP-binding ability, while it still retained the GTPase activity. On the other hand, the T42A/T43A mutant retained both the GTP-crosslinking and GTPase activities. However, the Km values for GTPase activity increased 5- and 12-fold for dE and T42A/T43A mutants, respectively. These results indicate that both the GTP-binding and GTPase activities are important for the Era function.

Reconstruction with bilateral gluteus maximus myocutaneous rotation flap after wide local excision for perianal extramammary Paget's disease. Report of two cases

PURPOSE

Extramammary Paget's disease is a rare dermatosis. Wide local excision is recommended in patients with perianal extramammary Paget's disease. After wide local excision, it is necessary to do reconstruction, with preservation of bowel function. We present here two cases of perianal Paget's disease, in which the patients were treated by reconstruction with bilateral gluteus maximus myocutaneous rotation flap after wide local excision.

PATIENTS AND METHODS

A 55-year-old woman and 58-year-old man were admitted with anal pain and bleeding. Histologic examination of the perianal lesion revealed the presence of typical Paget's cells, and no underlying carcinoma and no distant metastasis was detected in either patient. Wide local excision, including the rectal mucosa, was performed, with reference to intraoperative frozen sections. Surgical defect was overlapped with bilateral gluteus maximus myocutaneous rotation flap, and the anus was reconstructed.

RESULTS

Postoperative bowel function and quality of life were well preserved, and flaps healed satisfactorily. Patients have had no recurrence and have been able to return to work.

CONCLUSION

Bilateral gluteus maximus rotation flap may be useful after wide local excision of perianal extramammary Paget's disease without underlying invasive carcinoma.

Near-hexaploid Ph-positive acute myeloid leukemia with major-BCR/ABL transcript

We describe the first case of acute myeloid leukemia (AML) with a Philadelphia (Ph) translocation and a near-hexaploid range chromosome number, whose leukemic cells had the major-BCR/ABL transcript. The genesis of near-hexaploid leukemic cells might be due to endoreduplication of triploid leukemic cells with the Ph, since the relapsed leukemic cells had triploid range chromosomes with double Ph chromosomes.

The expression pattern of erythrocyte/megakaryocyte-related transcription factors GATA-1 and the stem cell leukemia gene correlates with hematopoietic differentiation and is associated with outcome of acute myeloid leukemia

To understand the clinical implications of transcription factors and their biologic roles during cellular differentiation in the hematopoietic system, we examined the expression of GATA-1, GATA-2, and stem cell leukemia (SCL) gene in human leukemia cell lines and various leukemia patients using the reverse transcriptase-polymerase chain reaction. Cell lines exhibiting megakaryocytic or erythrocytic phenotypes had GATA-1, GATA-2, and SCL gene transcripts, while monocytic cell lines had no detectable GATA-1, GATA-2, or SCL gene mRNA. In some myeloid cell lines, GATA-1 expression, but not SCL gene expression, was detected; GATA-1 expression in HL-60 cells was downregulated during the process of monocytic differentiation. We next examined GATA-1, GATA-2, and SCL gene expression in 110 leukemia samples obtained from 76 patients with acute myeloid leukemia (AML), 19 with acute lymphoblastic leukemia (ALL), and 15 with chronic myeloid leukemia in blast crisis (CML-BC). SCL gene expression was usually accompanied by GATA-1 expression and was preferentially detected in patients with leukemia exhibiting megakaryocytic or erythrocytic phenotypes, while patients with monocytic leukemia were clustered in the group with no detectable GATA-1 expression. None of the patients with ALL or CML-lymphoid-BC expressed SCL. De novo AML patients with SCL gene expression had a lower complete remission (CR) rate and had a significantly poorer prognosis. Among the patients with AML not expressing SCL, a high percentage of patients with CD7+ AML and CD19+ AML had detectable GATA-1, while patients with GATA-1-negative AML had the best CR rate (87.5%). Our results suggest that the expression pattern of transcription factors reflects the lineage potential of leukemia cells, and GATA-1 and SCL gene expression may have prognostic value for the outcome of patients with AML.

[Relation of serum fatty acids with serum lipids and blood pressure in women]

We studied the correlation of serum fatty acids, a potential coronary risk factor, with serum lipids and blood pressure. The subjects were women aged 40-69 of four Japanese populations (fishing, coastal farming, inland farming and urban populations) and a Caucasian population in which different dietary habits have been reported. Within populations, the total cholesterol level was not correlated with serum fatty acids. HDL-cholesterol was inversely correlated with saturated fatty acids and monounsaturated fatty acids, and positively correlated with polyunsaturated fatty acids although not significantly so in all populations. LDL-cholesterol was not correlated with saturated fatty acids and mono polyunsaturated fatty acids, but was positively correlated with polyunsaturated fatty acids. Triglyceride was positively correlated with saturated fatty acids and monounsaturated fatty acids, and inversely correlated with polyunsaturated fatty acids for all populations. Blood pressure correlated positively with saturated fatty acids, and inversely with polyunsaturated fatty acids although these associations were not statistically significant.

[Characteristics of participants in community-based rehabilitation programs and their levels of independence in activities of daily living]

To clarify characteristics of participants in community-based rehabilitation programs provided by local municipalities (cities, towns, and villages) and effect of the program on their levels of independence in activities of daily living (ADL), a cross-sectional study was performed on 422 participants in 49 municipalities in Kochi Prefecture. 1. Mean age of participants was 68.3 +/- 9.0, and 77.7% of them were stroke patients. 2. The mean interval between disease onset and program participation was 40.4 months, and the mean duration of program participation was 54.5 months. 3. At the start of rehabilitation programs and at the time of the investigation (December 1993), about 90% of the participants had good levels of independence in ADL (Rank A and over according to the standard of the Ministry of Health and Welfare). 4. The frequency of rehabilitation programs and the presence of occupational therapists were positively associated with the improvement of levels of independence in ADL. In particular, the frequency of rehabilitation programs was associated with improvement of quality of life in self-supporting participants (Rank J2), and the presence of occupational therapists was associated with the improvement of ADL in semi-bed-ridden participants (Rank A). 5. After adjusting for age and sex, using multiple logistic regression analysis, type of diseases (non-stroke), hospital rehabilitation immediately after onset, higher levels of independence in ADL at the start of rehabilitation programs, and higher frequency of rehabilitation programs were significantly associated with improvements in levels of independence in ADL. Shorter interval between disease onset and program participation, and the presence of occupational therapists were also associated with improvements in levels of independence in ADL, although the relation did not reach statistical significance.

Expression and functional analyses of the Dxpa gene, the Drosophila homolog of the human excision repair gene XPA

Xeroderma pigmentosum (XP) is a human hereditary disease characterized by a defect in DNA repair after exposure to ultraviolet light. Among the seven groups of XP, group A (XP-A) patients show the most severe deficiency in excision repair and a wide variety of cutaneous and neurological disorders. We have cloned homologs of the human XPA gene from chicken, Xenopus, and Drosophila, and sequence analysis revealed that these genes are highly conserved throughout evolution. Here, we report characterization of the Drosophila homolog of the human XPA gene (Dxpa). The Dxpa gene product shows DNA repair activities in an in vitro repair system, and Dxpa cDNA has been shown to complement a mutant allele of human XP-A cells by transfection. Polytene chromosome in situ hybridization mapped Dxpa to 3F6-8 on the X chromosome, where no mutant defective in excision repair was reported. Northern blot analysis showed that the gene is continuously expressed in all stages of fly development. Interestingly, the Dxpa protein is strongly expressed in the central nervous system and muscles as revealed by immunohistochemical analysis using anti-Dxpa antibodies, consistent with the results obtained in transgenic flies expressing a Dxpa-beta-galactosidase fusion gene driven by the Dxpa promoter.

In vivo evidence for involvement of a 58 kDa component of nuclear pore-targeting complex in nuclear protein import

We recently showed that a nuclear location signal (NLS)-containing karyophile forms a stable complex with cytoplasmic components for nuclear pore-targeting The complex, termed nuclear pore-targeting complex (PTAC), contained two essential proteins of 54 and 90 kDa, respectively, as estimated by electrophoresis. In this study, we found that the 54 kDa component of PTAC is the mouse homologue of Xenopus importin (m-importin). Cytoplasmic injection of the antibodies raised against recombinant m-importin showed an inhibitory effect on nuclear import of a karyophile in living mammalian cells. A portion of cytoplasmically injected antibodies migrated rapidly into the nucleus, indicating dynamic movement of this protein across the nuclear envelope. Moreover, the injected antibodies co-precipitated the karyophile, in an NLS-dependent manner, with endogenous m-importin in the cytoplasm. These results provide in vivo evidence that m-importin is involved in nuclear protein import through association with a NLS in the cytoplasm before nuclear pore binding.

The nuclear pore-targeting complex binds to nuclear pores after association with a karyophile

We recently showed that a karyophilic protein forms a stable complex, termed nuclear pore-targeting complex (PTAC), with cytoplasmic components prior to nuclear pore-binding. In this study, we cloned a cDNA encoding a 97 kDa of PTAC (PTAC97). Recombinant PTAC97 completely reconstitutes the nuclear binding-step in conjunction with a 58 kDa component of PTAC (PTAC58) in the semi-intact cell-free transport assay. Biochemical analysis reveals that PTAC58 binds to a karyophilic protein, and PTAC97 is associated with PTAC58 in a 1:1 molar ratio. A complex of PTAC97 and PTAC58 targets nuclear pores, depending on the presence of a karyophile. These in vitro results suggest that the first step in nuclear import occurs through the targeting-complex formation of a karyophile with PTAC58 bound to PTAC97.