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M Horikoshi

Publications and source records attributed to M Horikoshi.

At least 37 records · Page 2Linked to original sources
PubMed1998

Defect in cytokinesis of fission yeast induced by mutation in the WD40 repeat motif of a TFIID subunit.

BACKGROUND: TBP-associated factors contain a variety of structural motifs and their related in vivo significance has remained unclear. We have attempted to identify specific biological phenomena linked to a particular domain of a TAF by analysing domain-exchanged chimeric mutants between Schizosaccharomyces pombe (Sp) and Saccharomyces cerevisiae (Sc) counterparts. RESULTS: Contrary to the case of TBP, Sp TAF containing the WD40 repeat cannot be exchanged for its Sc counterpart, despite their highly conserved primary structures. This 'species-specific' function locates in the N-terminal region. The C-terminal region, largely consisting of the WD40 repeat, is exchangeable for the corresponding region of its Sc counterpart. Growth of the strain harbouring this C-terminal chimeric mutant is temperature-sensitive. The chimeric gene product did not disappear at a restrictive temperature, a finding which strongly suggests that the growth defect is caused by an aberration in the interactions through the WD40 repeat structural motif. With temperature elevation, the chimeric mutants underwent drastic morphological changes due to a defect in cytokinesis. CONCLUSIONS: The WD40 repeat of TAF is primarily involved in reactions which might regulate cytokinesis in Sp.

Cell Division↗
PubMed1998

Tip60 acetylates six lysines of a specific class in core histones in vitro.

BACKGROUND: Tip60, an HIV-1-Tat interactive protein, is a nuclear histone acetyltransferase (HAT) with unique histone substrate specificity. Since the acetylation of core histones at particular lysines mediates distinct effects on chromatin assembly and gene regulation, the identification of lysine site specificity of the HAT activity of Tip60 is an initial step in the analysis of its molecular function. RESULTS: Tip60 significantly acetylates amino-terminal tail peptides of histones H2A, H3 and H4, but not H2B, consistent with substrate preference on intact histones. Preferred acetylation sites for Tip60 are the Lys-5 of histone H2A, the Lys-14 of histone H3, and the Lys-5, -8, -12, -16 of histone H4, determined by a method which combined matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) measurements and Lys-C endopeptidase digestion, or a method detecting the incorporation of radiolabelled acetate into synthetic peptides. CONCLUSION: The lysine site specificity of Tip60 in histone amino-terminal tail peptides in vitro has been characterized by an assay measuring the molecular mass of endopeptidase digested peptides, or a previously described assay. These results agree well with our proposed classification of lysines in core histones. The classification may be useful for an analysis of the relationships between HATs and the substrates of other uncharacterized HATs.

Acetylation↗
PubMed1998

Isolation and initial characterization of GBF, a novel DNA-binding zinc finger protein that binds to the GC-rich binding sites of the HIV-1 promoter.

Human immunodeficiency virus (HIV) and its clinical syndrome, acquired immune deficiency syndrome (AIDS), are one of the world's most prominent health problems. To understand the mechanisms underlying HIV transcription and thereby its propagation, we have focused on the molecular interactions at the GC-rich binding sites of the HIV-1 core promoter, a region important for HIV-1 transcription. Previous biochemical studies have shown that Sp1, a zinc finger transcription factor initially isolated as a cellular factor binding that binds to the SV40 early promoter GC-rich sequence, binds to the HIV-1 GC-rich binding sites due to sequence similarities. However, the HIV-1 GC-rich binding sites are considerably different from the Sp1 consensus binding sequence, and recent genetic studies have shown the lack of regulation by Sp1 in numerous genes thought to be regulated by that factor in the past. We reasoned that other factors may bind to the HIV-1 GC-rich binding sites. Using the native HIV-1 GC-rich binding sequence as the bait, genetic screening for interacting factors was performed by the yeast one-hybrid method. A cDNA encoding a novel zinc finger protein named GBF, GC-rich sites binding factor, was isolated from a human peripheral blood leukocyte library. Primary structure analysis of GBF revealed a C2H2 Krüppel-type zinc finger at its C-terminus, and putative acidic and proline-rich domains at its N-terminus. We also show that GBF belongs to a subgroup of Krüppel-type zinc fingers distinct from Sp1. By directly addressing interactions at the HIV-1 GC-rich binding sites, our present study sheds new light on molecular interactions at the HIV-1 promoter.

Amino Acid Sequence↗
PubMed1998

Follow-up of patients with superior vena cava syndrome by functional analysis of radionuclide venography.

In addition to imaging, radionuclide venography can be used for studying haemodynamic changes in superior vena cava syndrome (SVCS) by using the indices of transit time (TT), time of half peak count (TH) and peak count ratio (PC ratio). The objective of this study was to examine the utility of applying these indices, alongside images, in the post-therapy assessment of SVCS patients. Radionuclide venography was performed twice on 36 patients with SVCS due to thoracic malignancies, 29 of whom received specific anti-cancer therapy between the two studies (Group I); the other 7 did not receive such therapy (Group II). On the images, 12 patients in Group I showed improvement, one a deterioration and 16 no change; in Group II, 4 showed a deterioration and 3 no change. Using the indices, nearly all patients in Group I had decreased post-therapy values indicating haemodynamic improvement. A significant difference was seen between the mean (+/- S.E.) pre- and post-therapy values for TT (pre vs post: 6.2 +/- 0.7 vs 2.7 +/- 0.3 s) and TH (pre vs post: 16.9 +/- 2.3 vs 7.9 +/- 0.8 s) (P < 0.001). Although the PC ratio showed a non-significant decrement, it related to the status of collateral change. The above indices provide clinically valuable information about the haemodynamic status of patients with SVCS and can be used for their post-therapy evaluation.

Adult↗
PubMed1997

Novel substrate specificity of the histone acetyltransferase activity of HIV-1-Tat interactive protein Tip60.

Tip60, originally isolated as an HIV-1-Tat interactive protein, contains an evolutionarily conserved domain with yeast silencing factors. We demonstrate here direct biochemical evidence that this domain of Tip60 has histone acetyltransferase activity. The purified recombinant effectively acetylates H2A, H3, and H4 but not H2B of core histone mixtures. This substrate specificity has not been observed among histone acetyltransferases analyzed to date. These results indicate that Tip60 is a histone acetyltransferase with a novel property, suggesting that Tip60 and its related factors may introduce a distinct alteration on chromatin.

Acetyltransferases↗
PubMed1997

Specific interactions and potential functions of human TAFII100.

Human transcription initiation factor TFIID contains the TATA-binding protein (TBP) and several TBP-associated factors (TAFs). To investigate the structural organization and function of TFIID, we have cloned and expressed a DNA encoding the third largest human TFIID subunit, hTAFII100. Immunoprecipitation studies demonstrate that hTAFII100 is an integral subunit that is associated with all transcriptionally-competent forms of TFIID. They further suggest that at least part of the N-terminal region lies on the surface of TFIID, while a C-terminal region containing conserved WD-40 repeats appears inaccessible. Both in vivo and in vitro assays indicate that hTAFII100 interacts strongly with the histone H4-related hTAFII80 and the histone H3-related hTAFII31, as well as a stable complex comprised of both hTAFII80 and hTAFII31. Apparently weaker interactions of hTAFII100 with TBP, hTAFII250, hTAFII28, and hTAFII20, but not hTAFII55, also have been observed. These results suggest a role for hTAFII100 in stabilizing interactions of TAFs, especially the histone-like TAFs, in TFIID. In addition, functional studies show that anti-hTAFII100 antibodies selectively inhibit basal transcription from a TATA-less initiator-containing promoter, relative to a TATA-containing promoter, suggesting a possible core promoter-specific function for hTAFII100.

Amino Acid Sequence↗
PubMed1997

Drosophila TAF(II)230 and the transcriptional activator VP16 bind competitively to the TATA box-binding domain of the TATA box-binding protein.

The transcription initiation factor TFIID, consisting of the TATA box-binding protein (TBP) and many TBP-associated factors (TAFs), plays a central role in both basal and activated transcription. An intriguing finding is that the 80-residue N-terminal region of Drosophila TAF(II)230 [dTAF(II)230-(2-81)] can bind directly to TBP and inhibit its function. Here, studies with mutated forms of TBP demonstrate that dTAF(II)230-(2-81) binds to the concave surface of TBP, which is important for TATA box binding. Previously, it was reported that a point mutation (L114K) on this concave surface destroys the ability of TBP to bind VP16 and to mediate VP16-dependent activation in vitro, but has no effect on basal transcription. Importantly, the same TBP mutation eliminates TBP binding to dTAF(II)230-(2-81). Consistent with these effects of the L114K mutation, dTAF(II)230-(2-81) and the VP16 activation domain compete for binding to wild-type TBP. These results indicate that transcriptional regulation may involve, in part, competitive interactions between transcriptional activators and TAFs on the TBP surface.

Amino Acid Sequence↗
PubMed1997

Molecular genetic elucidation of the tripartite structure of the Schizosaccharomyces pombe 72 kDa TFIID subunit which contains a WD40 structural motif.

BACKGROUND: The multisubunit general transcription factor termed TFIID is comprised of the TATA box DNA binding protein TBP and several TBP-associated factors termed TAFs. Current arguments regarding the mechanisms of regulation of transcription contend that TFIID makes multiple specific protein-protein interactions with numerous protein factors, and that these interactions are important for the regulation of transcriptional initiation. TAFs contain a variety of potential structural motifs and it has been speculated that these motifs participate directly in TAF function. However, to date the physiological significance of these putative structural motifs has not been systematically analysed in vivo. RESULTS: The essential gene encoding the Schizosaccharomyces pombe 72 kDa TFIID subunit is termed taf72+, which contains WD40 repeats, was cloned and sequenced. A comparison of the primary structure of this gene with its Drosophila and S. cerevisiae counterparts suggests the presence of regions that might play a role in TFIID function, due to the fact that significant portions of the sequences are highly conserved. Complementation analyses of a series of deletion mutants of this gene revealed that the most evolutionarily conserved regions of taf72+, including the WD40 repeats, are in fact indispensable for the viability. CONCLUSIONS: The 72 kDa subunit of S. pombe TFIID, which contains putative WD40 repeats, consists of three distinct functional domains separated by intervening regions. The functional significance of the WD40 repeats is demonstrated by this in vivo study.

Amino Acid Sequence↗
PubMed1997

The involvement of the histone fold motifs in the mutual interaction between human TAF(II)80 and TAF(II)22.

The TATA box-binding factor TFIID mediates transcriptional regulation through interactions with various regulatory factors and putative participation in reconfiguration of nucleosomes, utilizing its components, which include TATA box-binding protein (TBP) and TBP-associated factors (TAFs). Our and other previous studies have elucidated that there exist histone-similar TAFs. Studies on TAFs similar to histone H3 and H4 have revealed their biochemical and structural similarities to the corresponding histones. However, the existence of histone-like interactions involving the other TAFs is still ambiguous. Here we report the analyses with a two-hybrid system of the mutually interacting regions between hTAF(II)80 and hTAF(II)22, which resemble histone H4 and H2B, respectively. The results demonstrate the indispensability of the histone fold motifs of these two TAFs for mutual interaction. Together with earlier biochemical or structural studies, the present results suggest the presence of a histone octamer-like partial TAF complex and its involvement in transcription from chromatin templates.

Histones↗
PubMed1997

Restricted expression of a member of the transcription elongation factor S-II family in testicular germ cells during and after meiosis.

Whether expression of transcription elongation factors is regulated during development has not been investigated, though genes encoding elongation factor S-II are transcribed in a tissue-specific manner. We investigated the expression profile of tissue-specific S-II during development using an isolated cDNA, termed mouse S-II-T1, whose transcripts are detected almost exclusively in testis. Three experiments were performed with various types of germ and somatic cells in testis to determine in which cells S-II-T1 is expressed. (1) Expression of S-II-T1 is markedly reduced in the testes of adult WBB6F1-W/Wv mutant mice which lack testicular germ cells, indicating its expression is specific to testicular germ cells. (2) The onset of mouse S-II-T1 mRNA appearance in testis is seen about 10-14 days after birth, which is consistent with the start of meiotic events, suggesting that S-II-T1 is not transcribed in premeiotic and early meiotic cells such as spermatogonia, leptotene spermatocytes, or zygotene spermatocytes. (3) Mouse S-II-T1 transcripts accumulate in meiotic pachytene spermatocytes and are detected in postmeiotic haploid cells such as round and elongated spermatids during spermatogenesis, as shown by fractionation of testicular germ cells at four different stages. These results indicate that expression of mouse S-II-T1 is restricted to testicular germ cells during and after meiosis in the course of spermatogenesis. This is the first report that expression of a transcription elongation factor in particular cells is regulated in a stage-specific manner in the course of development.

Amino Acid Sequence↗
PubMed1997

[A case of atrial septal defect complicated by persistent left superior vena cava in whom hemophagocytic syndrome appeared after operation].

The patient was a 22-year-old woman and suffered from atrial septal defect (ASD) complicated by persistent left superior vena cava (PLSVT). The patient underwent a patch closure using calf pericardium. Despite favorable progress immediately after the operation, fever, enlarged cervical lymph nodes, and leukocytopenia appeared beginning day 8 after the operation. Based on the results of cytodiagnosis of myeloaspiration specimen, the diagnosis of hemophagocytic syndrome (HPS) was made. Since an elevation of 2-5 oligo A synthetase (2-5 AS) levels was observed, the patient was diagnosed to suffer from virus-associated hemophagocytic syndrome (VAHS), and steroid was administered. The patient exhibited a good response to the treatment. The fever declined 3 days after the start of administration. Leukocyte counts were also increased gradually. The patient condition was improved and she was discharged from the hospital on day 28. At present, seven months after the operation, there is no evidence of recurrence and the patient's condition is still monitored.

Adult↗
PubMed1997

[A case of coronary artery bypass grafting without cardiopulmonary bypass in a patient with left ventricular dysfunction].

A 54-year-old man who had severe deterioration of left ventricular function (cardiac index ; 1.6 l/min/m2, left ventricular ejection fraction ; 26%) due to two myocardial infarcts underwent bypass of the left anterior descending artery using the left internal thoracic artery under IABP assist without extracorporeal circuration or cardiac arrest. Two hours postoperatively, he was extubated. Subsequent clinical course was uneventful with a satisfactory outcome. These findings suggest that coronary artery bypass without extracorporeal circulation or cardiac arrest is a safe and effective procedure in patients with left ventricular dysfunction.

Cardiopulmonary Bypass↗
PubMed1996

Cloning of the cDNA encoding a novel subtype of histone H1.

The H1 class of histones is implicated in organizing a higher order of chromatin structure and in involvement with transcriptional repression. They compromise multiple subtypes that presumably have a specific function. We report here the isolation and characterization of a human cDNA encoding a novel subtype of histone H1. It is the most distantly related subtype of mammalian H1 reported to date. However, it still shares the characteristic features of H1: the tripartite structure, conservation in the globular domain, the profile of hydropathy and the basic isoelectric point. The expression of this H1 subtype was ubiquitously observed in all tissues examined. Our findings suggest that novel subtypes of H1 may remain unidentified in mammals.

Amino Acid Sequence↗
PubMed1996

Isolation of Xenopus laevis TFIID subunit p22 reveals two distinct structural regions.

A cDNA clone encoding a Xenopus laevis (Xl) homologue of the TATA box-binding factor TFIID subunit p22, which shows similarities to histones H2B and H3, was isolated and sequenced. The deduced 164-amino-acid (aa) sequence was compared to those of homologues cloned from human and Drosophila melanogaster (Dm). Analysis showed that the TFIID subunit p22 consists of an approx. 60-aa less-conserved N-terminus and approx. 100-aa highly-conserved C terminus.

Amino Acid Sequence↗
PubMed1996

Isolation and characterization of a cDNA encoding a novel human transcription factor TFIID subunit containing similarities with histones H2B and H3.

Using the yeast two-hybrid system, we isolated a human cDNA that encodes a protein (hp22) interacting with TATA box-binding factor TFIID subunit p80 containing similarity with histone H4. Sequence analysis showed that the open reading frame (ORF) specifies a 161-amino-acid (aa) polypeptide homologous to Drosophila melanogaster TFIID subunit p22 (dp22). Comparison of the aa sequence of human TFIID subunit p22 (hp22) with that of dp22 revealed that p22 is composed of two distinct regions; the less conserved N-terminal (20% identity) and the highly conserved C-terminal (65% identity) regions. Additionally, the C-terminal region was found to contain similarities with histones H2B and H3. Northern blot analysis showed mRNA corresponding to hp22 to be expressed in all tissues examined.

Amino Acid Sequence↗
PubMed1996

Isolation and characterization of a cDNA encoding a human TFIID subunit containing a variety of putative structural motifs including direct repeats.

A cDNA encoding human TFIID subunit p30 beta (hp30 beta) was isolated and sequenced. Comparison of the deduced 211 amino acid (aa) sequence with that of Drosophila melanogaster p30 beta (dp30 beta) showed 45% identity in overall length, and subunits with highly conserved C-terminal (81% identity) and less conserved N-terminal (21% identity) regions. Three acidic and basic regions were alternately placed. Potent target sites for protein kinases and a putative nuclear localization signal (NLS) were located in the N-terminal region. Interestingly, analysis of the aa sequence of p30 beta led us to find several interesting structural motifs/regions including 1) direct repeats, 2) a region similar to histone H4 between the two direct repeats and 3) acidic and hydrophobic aa surfaces in the potent helical region. Northern blot analysis showed ubiquitous expression of mRNA corresponding to hp 30 beta.

Amino Acid Sequence↗