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Biomedical subjects

M Saijo

Publications and source records attributed to M Saijo.

At least 55 records · Page 3Linked to original sources
PubMed1997

DNA damage recognition by XPA protein promotes efficient recruitment of transcription factor II H.

The human basal transcription factor IIH (TFIIH) is an essential component of the nucleotide excision repair machinery. TFIIH is required for reaction steps concomitant with or prior to the formation of dual incisions in the damaged DNA strand. To understand the mechanism underlying the recruitment of TFIIH to DNA damage sites we have analyzed i) the direct affinity of TFIIH for damaged or undamaged DNA and ii) the interaction of TFIIH with XPA.DNA complexes, formed using unirradiated or UV-irradiated DNA. Filter binding assays showed that TFIIH has some affinity for the DNA, but in contrast to XPA, does not show any preference for UV-irradiated DNA. Pull-down experiments demonstrated that TFIIH binds to XPA.DNA complexes in an UV damage-dependent manner by a direct protein-protein interaction with XPA. We propose that an enhancement of the affinity of XPA protein for TFIIH could arise from conformational changes of XPA when it binds to UV lesions on the DNA.

DNA↗
PubMed1997

Mutations in the XPD gene leading to xeroderma pigmentosum symptoms.

XP is a sun-sensitive and cancer-prone genetic disorder, consisting of eight (group A-G) genetically distinct complementation groups. Some XP group D patients exhibit clinical symptoms of other genetic disorders, CS, and TTD. The XP group D gene (XPD gene) product is required for nucleotide excision repair and is one of the components of basal transcription factor TFIIH as well. Therefore, different mutations in the XPD gene may result in a variety of clinical manifestations. Here we report on two causative mutations of the XPD gene in XP61OS, a Japanese XP group D patient who has only mild skin symptoms of XP without CS, TTD, or other neurological complications. One of the mutations was the 4-bp deletion at nucleotides 668-671, resulting in frameshift and truncation of the protein. The other was a nucleotide substitution leading to Ser-541 to Arg (S541R) in helicase domain IV of the XPD protein. The patient's father was heterozygous for the 4-bp deletion, while the mother was heterozygous for the S541R mutation. Thus, the parents were obligate carriers of the XP-D trait. The expression study showed that the XPD cDNA containing the deletion or the S541R missense mutation failed to restore the UV sensitivity of XP6BE, group DaXP cells, while the wild-type XPD cDNA restored it to the normal level. However, the transfectant expressing the XPD cDNA with the missense mutation was slightly more resistant than the parental XP6BE cells. These findings are consistent with the mild symptoms of the XP61OS patient.

Cells, Cultured↗
PubMed1997

Analysis of the non-sense mutants of varicella-zoster virus thymidine kinase.

Three non-sense mutants of varicella-zoster virus (VZV) thymidine kinase (TK) gene, VZTK325, VZTK278 and VZTK224, were isolated. The mutants had a single nucleotide substitution at codons 326, 279 and 225, which changed the codon of TGG (tryptophan) to the stop codon TGA. The wild type (WT) and mutant TKs were expressed in E. coli cells and their characteristics were evaluated. VZTK224 lost TK activity, but VZTK325 and VZTK278 maintained 74.8% and 21.2% of the WT TK activity. On the other hand, all mutants lost the thymidylate kinase activity. Moreover, VZTK325 and VZTK278 polypeptides were heat-labile. These data suggest that the carboxy-terminal portion of herpesvirus TK plays an important role in the stable folding of TK and thymidylate kinase activity.

Heating↗
PubMed1997

Epidemiology of influenza virus infections in children with acute respiratory infections in Zambia.

A viral aetiological and epidemiological study of acute respiratory infections (ARI) in children was carried out in Lusaka, Zambia between June 1993 and September 1995. A total of 3,760 throat swab specimens were collected for virus isolation from children under 5 years of age who had ARI and were attending three health centres in Lusaka. Between June and November 1993, 52 cases of the influenza A/H3N2 viruses were isolated. Between May and July 1994, 34 influenza B cases were isolated. In 1995, one A/H3N2 influenza virus was isolated in January and then the same type of influenza virus was isolated from 55 samples between June and August. The isolation rate of influenza virus was highest at 14.3% (20/139) in August 1993, at 15.1% (18/119) in June 1994 and at 25.4% (43/169) in July 1995. This is the first report of a consecutive study of influenza virus infections in Zambia and the results reveal that influenza virus infections are one of the most important pathogens of ARI in children in the cool, dry season (June-August) in this country.

Acute Disease↗
PubMed1997

[Trend of bacterial meningitis in children over a 14 year period (1981 through 1994) in Japan--an analysis based on studies in 27 institutions].

We observed 266 children with purulent meningitis in 27 institutions in Japan during the 14 years from 1981 on dividing these years into 3 periods, 1981-1985, 1986-1990 and 1991-1994, and studied the trend of causative organisms identified in 254 among the 266 patients. Their ages were less than 3 months after birth in 50 children and 3 months or older in 216: there were 141 boys and 125 girls. The causative organisms were H. influenzae in 134 patients and S. pneumoniae in 50, most of them being aged 3 months or older. Next to the above bacteria ranked S. agalactiae in 29 and E. coli in 12, many of the patients were aged less than 3 months. Staphylococcus spp. was found in 7 patients and about 70% of them were aged 3 months or older. L. monocytogenes was found in 4 patients and N. meningitidis in 3 and they were aged 3 months or older in both patient groups. S. pyogenes, Enterococcus spp., Peptostreptococcus spp., P. Mirabilis and Enterobacter spp. were detected each in 1 patient. The causative organism was unknown in 21 patients and there was no double infection. H. influenzae were detected in 18 patients in 1981-1985 period (36.7%), in 56 in 1986-1990 (54.9%) and in 60 in 1991-1994 (63.8%) showing an increasing tendency, but S. pneumoniae exhibited neither an increasing nor decreasing tendency. There was a decreasing tendency with S. agalactiae and E. coli, but the details were not clear because there were few patients aged less than 3 months. Although the period of coexistence of 4 main bacterial species was not made clear in this study. Listeria is considered to develop mainly in the early childhood, and we believe that the conventional way of using a cephem preparation and ampicillin combined for patients under 6 years need not be altered. However, panipenem (phonetic) is likely to be effective for insensible S. pneumoniae for the time being.

Escherichia coli↗
PubMed1997

[Central nervous system infection caused by mumps virus].

Central nervous system infection caused by mumps virus is reviewed. Aseptic meningitis, acute encephalitis, chronic encephalitis, hydrocephalus, ataxia, transverse myelitis, Guillain-Barré syndrome and deafness are noted as central nervous system complications of mumps. Among these complications, acute and chronic encephalitis, hydrocephalus, transverse myelitis and deafness occasionally result in severe sequelae. Aseptic meningitis due to mumps vaccine strain increased significantly after the introduction of trivalent measles, mumps and rubella vaccination in Japan. Recently, a differentiation method of mumps vaccine strain from wild viruses has been established using molecular analysis. Mumps virus infection is still one of the most common communicable viral infections, although it is preventable by vaccination. We emphasize the importance of mumps vaccination to prevent such severe complications as encephalitis and deafness.

Central Nervous System Diseases↗
PubMed1996

Sequential binding of DNA repair proteins RPA and ERCC1 to XPA in vitro.

Recent studies have shown that many proteins are involved in the early steps of nucleotide excision repair and that there are some interactions between nucleotide excision repair proteins, suggesting that these interactions are important in the reaction mechanism. The xeroderma pigmentosum group A protein (XPA) was shown to bind to the replication protein A (RPA) or the excision repair cross complementing rodent repair deficiency group 1 protein (ERCC1), and these interactions might be involved in the damage-recognition and/or incision steps, of nucleotide excision repair. Here we show that the XPA regions required for the binding to the 70 and 34 kDa subunits of RPA are located in the middle and on N-terminal regions of XPA, respectively. These regions do not overlap with the ERCC1-binding region of XPA, and a ternary protein complex of RPA, XPA and ERCC1 was detected in vitro. In addition, using the surface plasmon resonance biosensor, the binding of RPA and ERCC1 to XPA was investigated. The dissociation constants (KD) of RPA and ERCC1 with XPA were 1.9 x 10(-8 )and 2.5 x 10(-7) M, respectively. Moreover, our results suggest the sequential binding of RPA and ERCC1 to XPA.

Binding Sites↗
PubMed1996

Phosphorylation-independent stimulation of DNA topoisomerase II alpha activity.

It has been suggested that casein kinase II phosphorylates DNA topoisomerase II alpha (topo II alpha) in mouse FM3A cells, by comparison of phosphopeptide maps of topo II alpha labeled in intact cells and of topo II alpha phosphorylated by various kinases in vitro. The phosphorylation of purified topo II alpha by casein kinase II, which attached a maximum of two phosphate groups per topo II alpha molecule, had no effect on the activity of topo II alpha. Dephosphorylation of purified topo II alpha by potato acid phosphatase, which almost completely dephosphorylated the topo II alpha, did not reduce the activity of topo II alpha. The incubation itself, regardless of phosphorylation or dephosphorylation status, stimulated the enzyme activity in both reactions. Topo II alpha activity was stimulated by incubation in a medium containing low concentrations of glycerol but not in that containing high concentrations of glycerol, such as the 50% in which purified topo II alpha is stored. The stimulation of topo II alpha activity by incubation was dependent on the concentration of topo II alpha, requiring a relatively high concentration of topo II alpha.

Animals↗
PubMed1996

Identification of a damaged-DNA binding domain of the XPA protein.

The XPA (xeroderma pigmentosum group A) protein is a zinc metalloprotein consisting of 273 amino acids which binds preferentially to UV- or chemical carcinogen-damaged DNA, suggesting that it is involved in the recognition of several types of DNA damage during nucleotide excision repair processes. Here we identify a DNA binding domain of the XPA protein. The region of the XPA protein responsible for preferential binding to DNA damaged by UV or cis-diammine-dichloroplatinum(II) (cisplatin) is contained within a truncated derivative of the XPA protein, MF122, consisting of 122 amino acids and containing a C4 type zinc finger motif. CD (circular dichroism) measurements of the MF122 protein showed that it has a helix-rich secondary structure, suggesting that it is a discretely folded, functional mini-domain. The MF122 protein should be useful for structural investigation of the XPA protein and of its interaction with damaged DNA.

Base Sequence↗
PubMed1996

Emotional disturbances in trauma patients during the rehabilitation phase: studies of posttraumatic stress disorder and alexithymia.

Recent studies have shown a partial similarity between posttraumatic stress disorder (PTSD) and alexithymia. In this study, the authors examined the relationship between PTSD and alexithymia in two samples of 26 patients with burn injury and 27 patients with digit amputation during rehabilitation. The prevalence rates of DSM-III-R PTSD and alexithymia assessed by the Toronto Alexithymia Scale (TAS) were significantly higher for injury patients than for healthy volunteers. The rate of PTSD symptoms of avoidance and emotional numbing was significantly and positively correlated with the TAS scores in injury patients. The PTSD symptoms of avoidance and emotional numbing had a significant relationship with function after digit replantation. Alexithymia also had a similar relationship with physical conditions. These results suggest that 1) in some cases, alexithymia may be evident when PTSD emotional symptoms appear in injury patients, and 2) emotional disturbances (i.e., PTSD symptoms of avoidance and emotional numbing and alexithymia) may be influenced by the level of functional recovery after digit replantation.

Adult↗
PubMed1996

White blood cell count, C-reactive protein and erythrocyte sedimentation rate in respiratory syncytial virus infection of the lower respiratory tract.

Laboratory findings such as white blood cell (WBC) count, C-reactive protein (CRP) concentration and erythrocyte sedimentation rate (ESR) level in patients with bronchiolitis, bronchopneumonia and lobar pneumonia caused by respiratory syncytial virus (RSV) were studied. The diagnosis of having RSV infection of the lower respiratory tract was made on the presence of RSV antigen in nasopharyngeal specimens by means of enzyme immunoassay, on chest X-ray appearances and clinical manifestations. The WBC counts in the lobar pneumonia cases (n = 25, 12,288 +/- 6296/mm3) were significantly greater than those for the bronchiolitis (n = 52, 9562 +/- 2720/mm3) and bronchopneumonia (n = 43, 8369 +/- 3714/mm3) cases. The concentrations of CRP in lobar pneumonia cases (n = 25, 6.5 +/- 7.3 mg/dL) were significantly greater than those in the bronchiolitis (n = 52, 1.9 +/- 2.0 mg/dL) and bronchopneumonia (n = 43, 2.1 +/- 2.4 mg/dL) cases. The ESR levels in the lobar pneumonia cases (n = 24, 43.8 +/- 29. mm/h) were also significantly higher than those in the bronchiolitis (n = 34, 20.1 +/- 12.3 mm/h) and bronchopneumonia (n = 40, 24.7 +/- 15.9 mm/h) cases. There were no significant differences in the WBC counts, the CRP concentrations and ESR levels between the bronchiolitis and bronchopneumonia cases. These results suggest that the RSV lobar pneumonia cases are coinfected with some bacterial organisms more heavily than in the RSV bronchiolitis and bronchopneumonia cases.

Blood Sedimentation↗
PubMed1996

Truncated XPA protein detected in atypical group A xeroderma pigmentosum.

XPA protein from a patient with typical group A xeroderma pigmentosum (XP) and three atypical group-A XP patients were analysed. Immunoblot analysis of XPA proteins revealed that a typical group-A XP patient showed no XPA protein band, while a smaller, truncated XPA protein, which appears to be responsible for mid skin lesions and minimal neurological abnormalities, was detected in cells from three atypical group-A XP patients. Furthermore, the difference in the amount of truncated XPA protein correlated with the mildness of neurological manifestations in these three atypical group-A XP patients. The results suggest a correlation between clinical manifestations and qualitative and quantitative abnormalities of XPA protein products.

Adolescent↗
PubMed1995

cDNA sequence and chromosomal localization of a novel human protein, RBQ-1 (RBBP6), that binds to the retinoblastoma gene product.

We have previously isolated cDNA of a novel protein (RBQ-1, HGMW-approved symbol RBBP6) that binds to the retinoblastoma gene product (pRB). Total nucleotide sequence of the cDNA has now been determined. It encoded a protein of 140 kDa that consists of 948 amino acids and contains multiple repeated sequences like SRS, YRE, and VPPP. The region used for pRB binding was identified on a small region near the C-terminus. We have mapped this gene to 16p11.2-p12 using polymerase chain reaction analysis on a human-hamster hybrid cell panel and chromosomal fluorescence in situ hybridization.

Amino Acid Sequence↗
PubMed1995

70-kDa heat shock cognate protein interacts directly with the N-terminal region of the retinoblastoma gene product pRb. Identification of a novel region of pRb-mediating protein interaction.

Retinoblastoma protein (pRb) functions as a tumor suppressor, and certain proteins are known to bind to pRb in the C-terminal region. Although the N-terminal region of pRb may also mediate interaction with some proteins, no such protein has been identified yet. We demonstrated previously the in vivo protein association between pRb and 73-kDa heat shock cognate protein (hsc73) in certain human tumor cell lines. In this report we analyzed the interaction between these two proteins in vitro. Our data showed that hsc73 interacts with the novel N-terminal region of pRb; that is, pRb binds directly to hsc73 and dissociates from hsc73 in an ATP-dependent manner. By using deletion mutants of cDNA encoding pRb, the hsc73 binding site of pRb was determined to be located in the region (residues 301-372) outside the so-called A pocket (residues 373-579) of this tumor suppressor protein. This finding was compatible with the fact that the adenovirus E1A oncoprotein, which is known to bind to the E2F binding pocket region of pRb, could not compete with hsc73 for the binding. Furthermore, phosphorylation of pRb by cyclin-dependent kinase inhibited the binding of pRb to hsc73. These data suggest that hsc73 may act exclusively as the molecular chaperone for nonphosphorylated pRb. As a result, hsc73 may function as a molecular stabilizer of nonphosphorylated pRb.

Adenosine Triphosphate↗
PubMed1995

High incidence of ultraviolet-B-or chemical-carcinogen-induced skin tumours in mice lacking the xeroderma pigmentosum group A gene.

Xeroderma pigmentosum (XP) is an autosomal recessive disorder characterized by a high frequency of skin cancer on sun-exposed areas, and neurological complications. XP has a defect in the early step(s) of nucleotide-excision repair (NER) and consists of eight different genetic complementation groups (groups A-G and a variant). We established XPA (group-A XP) gene-deficient mice by gene targeting of mouse embryonic stem (ES) cells. The XPA-deficient mice showed neither obvious physical abnormalities nor pathological alterations, but were defective in NER and highly susceptible to ultraviolet-B- or 9,10-dimethyl-1,2-benz[a]anthracene-induced skin carcinogenesis. These findings provide in vivo evidence that the XPA protein protects mice from carcinogenesis initiated by ultraviolet or chemical carcinogen. The XPA-deficient mice may provide a good in vivo model to study the high incidence of skin carcinogenesis in group A XP patients.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1995

Enhancement of damage-specific DNA binding of XPA by interaction with the ERCC1 DNA repair protein.

The human XPA and ERCC1 proteins, which are involved in early steps of nucleotide excision repair of DNA, specifically interacted in an in vitro binding assay and a yeast two-hybrid assay. A stretch of consecutive glutamic acid residues in XPA was needed for binding to ERCC1. Binding of XPA to damaged DNA was markedly increased by the interaction of the XPA and ERCC1 proteins. ERCC1 did not enhance binding to DNA when a truncated XPA protein, MF122, was used in place of the XPA protein. MF122 retains damaged DNA binding activity but lacks the region for protein-protein interaction including the E-cluster region. These results suggest that the XPA/ERCC1 interaction may participate in damage-recognition as well as in incision at the 5' site of damage during nucleotide excision repair.

Binding Sites↗
PubMed1995

Molecular cloning of a human protein that binds to the retinoblastoma protein and chromosomal mapping.

We have isolated distinct clones for cellular proteins that bind to the retinoblastoma protein by direct screening of cDNA expression libraries using purified pRB as a probe. The total nucleotide sequence of one of these clones, RBQ-3, was determined and found to encode a protein of 66 kDa localized in the nucleus. The RBQ-3 preferentially binds to underphosphorylated pRB. The region used for binding to this protein was mapped to the E1A-binding pocket B of pRB, which has sequence similarity to the general transcription factor TFIIB. We have mapped the gene to 1q32 using polymerase chain reaction analysis on a human-hamster hybrid cell panel and chromosomal fluorescence in situ hybridization.

Amino Acid Sequence↗