Proceedings of the Japan Academy, Series B

Original Papers

Experimental study of the transition time of convection patterns and its application to the Wilson cycle

Takatoshi YANAGISAWA, Yozo HAMANO

2003 Volume 79B Issue 4 Pages 99-104
Published: 2003
Released on J-STAGE: May 19, 2004

DOIhttps://doi.org/10.2183/pjab.79B.99

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We studied the influence of the inhomogeneous boundary conditions on the convection pattern and the response of the pattern to the change of these conditions. These are the idealized models for drifting continental tectospheres at the surface of the Earth. Continental tectosphere acts as a thermal insulator and it can regulate convection upwelling region to come below it. We investigated the transition time of convection patterns and found out that it is much longer than the flow circulation time under some conditions. The Earth satisfies this condition at present; hence we can explain the time scales for aggregation and breakup of continents.

(Communicated by Ikuo KUSHIRO, M. J. A., April 14, 2003)

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First oncocerid cephalopod from Japan

Shuji NIKO, Tamio NISHIDA

2003 Volume 79B Issue 4 Pages 105-107
Published: 2003
Released on J-STAGE: May 19, 2004

DOIhttps://doi.org/10.2183/pjab.79B.105

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The two Lochkovian (Early Devonian) specimens of karocerartid cephalopod from the Fukuji Formation, Gifu Prefecture represent the first record of the order Oncocerida in Japan, and constitute the basis for a new species, Ankyloceras takii. This species is morphologically closest to Ankyloceras accomodatum Zhuravleva and A. virgulaforme (Foerste) both from the early Lochkovian of Novaya Zemlya. Paleobiogeographic implications of the present discovery are discussed.

(Communicated by Tatsuro MATSUMOTO, M. J. A., April 14, 2003)

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Knudson’s two hits, both associated with the insertions of genetic mobile elements in a rat pituitary adenoma

Kazunori KAJINO, Okio HINO

2003 Volume 79B Issue 4 Pages 108-113
Published: 2003
Released on J-STAGE: May 19, 2004

DOIhttps://doi.org/10.2183/pjab.79B.108

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The Eker rat bears a germline mutation of the tumor suppressor Tsc2 gene with insertion of a retrotransposon, intracisternal A particle (IAP). With a second somatic mutation of the Tsc2 gene, virtually all Eker rats develop renal carcinoma. Furthermore, some of them develop pituitary adenomas which are also caused by a second hit mutation in the Tsc2 gene. Previously we found an Eker rat pituitary adenoma case with a rearranged Tsc2 gene by Southern blot analysis. In this study we determined its structure, and found that another retrotransposon, LINE1, was involved in the rearrangement of the wild type Tsc2 allele. To our knowledge, this is the first case of Knudson’s two hits associated with two retrotransposons.

(Communicated by Masanori OTSUKA, M. J. A., April 14, 2003)

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Characteristics of DNA superstructures formed upon interaction with feast/famine regulatory proteins, FFRPs

Masashi SUZUKI, Hideaki KOIKE

2003 Volume 79B Issue 4 Pages 114-119
Published: 2003
Released on J-STAGE: May 19, 2004

DOIhttps://doi.org/10.2183/pjab.79B.114

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By analyzing the 3D structures of full length FFRPs, which were crystallized previously in the absence of DNA, characteristics of DNA superstructures formed upon interaction with these proteins have been predicted. A pair of α-helices 3 in an FFRP dimer are positioned, so that they will bind to two DNA sites separated by 9, or a slightly fewer, basepairs. The nucleotide sequences of the two DNA sites will be reverse complementary to each other, reflecting the symmetric positioning of the two recognition helices. With this DNA fragment embedded in the center of a unit of ∼20 basepairs, four such units, altogether of ∼80 basepairs, will circle around the disk-like assembly of FFRP. Around each helical turn of the cylindrical assembly of FFRP, six such units, i.e. ∼120 basepairs, would wrap.

(Communicated by Masanori OTSUKA, M. J. A., April 14, 2003)

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DNA-binding activity of p100, a transcriptional coactivator, to single-stranded C-rich sequences

Hirokazu FUKUDA, Naoto TSUCHIYA, Maiko SATO, Akira YAMAGUCHI, Nanae TA ...

2003 Volume 79B Issue 4 Pages 120-123
Published: 2003
Released on J-STAGE: May 19, 2004

DOIhttps://doi.org/10.2183/pjab.79B.120

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We have recently identified and purified six minisatellite Pc-1 binding proteins (MNBPs), which bind to mouse hypervariable minisatellite Pc-1, from nuclear extracts of NIH3T3 cells. In the present paper, we describe one of those MNBPs, MNBP-G, that binds to single-stranded d(CTGCC)_n. Amino acid sequences of three proteolytic peptide fragments of MNBP-G were determined and cDNA clones isolated. MNBP-G was thereby proved identical to the transcriptional coactivator protein, p100. The mRNA was expressed ubiquitously but particularly strongly in liver, heart, and kidney. Recombinant p100 bound to single-stranded d(CTGCC)_n and other C-rich sequences, such as d(CCTGCC)_n, d(CTTCC)_n, and d(C)_n, but not to their complementary G-rich sequences or double-stranded forms. The DNA-binding ability of p100 demonstrated here suggests an involvement in transcriptional activating processing, in addition to its bridging activity between transcription factors and the basal transcription machinery reported previously.

(Communicated by Tamio YAMAKAWA, M. J. A., April 14, 2003)

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