Biomedical subjects

K W Makabe

Publications and source records attributed to K W Makabe.

22 records · Page 2Linked to original sources

PubMed1993

A complementary DNA for an ascidian embryonic nuclear antigen Hgv2 encodes a protein closely related to the amphibian histone-binding protein N1.

We have isolated and sequenced a cDNA clone encoding an ascidian embryonic nuclear protein, Hgv2. An insert about 2 kb long covered almost the entire length of 2.3-kb Hgv2 mRNA. The amino acid sequence of Hgv2 deduced from the cDNA sequence showed that this protein is related to the amphibian karyophilic histone-binding protein N1, which is thought to be involved in nucleosome assembly. Homology between these two proteins is evident from their extremely similar amino acid compositions and hydropathy profiles. In addition, Hgv2 protein has sequences strikingly similar to the nuclear targeting signal of N1. This is therefore the first report of molecular cloning of a homologue of N1 in non-amphibian species. Putative histone-binding domains of N1 are composed of two acidic residue-rich clusters. Hgv2 polypeptide contains two highly acidic regions, but amino acid sequences of the regions are not conserved. Since Hgv2 protein exists in nuclei of every embryonic cell but disappears from nuclei of metamorphosed juvenile tissues, this protein may function as a nucleosome assembly factor during rapid embryonic cell divisions.

Amino Acid Sequence↗

PubMed1993

Novel genes expressed differentially in ascidians with alternate modes of development.

We have used a subtractive procedure to isolate cDNA clones encoding genes expressed differentially in ascidian species with alternate modes of development. The ascidians used in this study were Molgula occulta, which develops a tailed (urodele) larva, and Molgula occulta, which develops a tailless (anural) larva. Two of the identified clones, Uro-2 and Uro-11, are described. Southern blots show that the Uro-2 and Uro-11 genes are present in both species, but the corresponding mRNAs are expressed preferentially in the urodele species. In situ hybridization showed that Uro-2 and Uro-11 transcripts accumulate in small oocytes during oogenesis. The maternal Uro-2 and Uro-11 transcripts were distributed throughout the oocyte cytoplasm. Transcript concentrations declined during vitellogenesis, but mature eggs still contain detectable levels of Uro-2 and Uro-11 mRNA. After fertilization, the maternal Uro-2 and Uro-11 transcripts were localized in the ectoplasm of uncleaved zygotes and mostly entered the ectoderm cells during cleavage. The Uro-2 gene appears to produce only maternal transcripts. In contrast, the Uro-11 gene may also produce zygotic transcripts, which accumulate between gastrulation and neurulation in posterior epidermis, neural and tail muscle cells. Zygotic expression of the Uro-11 gene was not detected in embryos of the anural species. The deduced amino acid sequences of the Uro-2 and Uro-11 cDNAs suggest that they encode novel basic proteins with distinctive structural features. The predicted Uro-2 protein contain, a leucine zipper motif, suggesting that it may dimerize with another protein. The predicted Uro-11 protein contains a nuclear localization signal, a region with similarity to part of the DNA-binding motif in the bacterial histone-like HU and IHF proteins, 12 repeats of the proposed DNA-binding motif S(T)PXX, and a potential zinc finger of the C6 or C6H2 class, suggesting that it may be a DNA-binding protein. The Uro-2 and Uro-11 proteins are candidates for regulatory factors involved in the evolutionary transition from urodele to anural development.

Amino Acid Sequence↗

PubMed1992

Tunicate muscle actin genes. Structure and organization as a gene cluster.

We have isolated and determined the complete nucleotide sequences of two genes, HrMA4a and HrMA2, which encode the same muscle actin protein of the tunicate Halocynthia roretzi. HrMA4a and HrMA2 contain three exons, and the genes have intron-exon splice junctions at the same positions. The 5' flanking region of HrMA4a gene contains several potential regulatory elements. A TATA box is located at -30 and a CArG box found in regulatory region of vertebrate muscle-specific genes is located at -116. Seven E-box consensus sequences (CANNTG) known as binding sites for vertebrate myogenic determination factors are found within a 500 base-pair portion of the 5' flanking region of HrMA4a gene. HrMA4a and HrMA2 are separated by 1600 bases in genomic DNA and transcribed in the same direction. In addition to these genes, we have identified three other actin genes encoding muscle-type actins. All five actin genes are located in a 30 x 10(3) base-pair region of the genome and aligned in the same direction. This is the first report of a cluster of "vertebrate-type" muscle actin genes. The consensus sequences of 5' flanking region are conserved among these five genes, suggesting that the expression of the genes is controlled coordinately. This may be advantageous for the accumulation of considerable amounts of actin proteins in rapidly developing embryos of this animal.

Actins↗

PubMed1991

Molecular cloning and expression of a novel homeobox gene AHox1 of the ascidian, Halocynthia roretzi.

We have isolated a novel ascidian homeobox gene, designated AHox1, by screening the genomic DNA of Halocynthia roretzi with the Bombyx mori Antennapedia type homeobox as a probe. The AHox1 gene encodes a protein that consists of 741 amino acids. The homeobox of AHox1 is interrupted by 2 introns each of which is about 300 bp in length and it shows about 70% similarity at a deduced amino acid level to that of Drosophila H2.0. This suggests that AHox1 is one of the most diverged homeobox genes so far characterized. Northern blot hybridization with an AHox1 probe showed the presence of single transcripts approximately 2.8 kb in length in larvae, juveniles and some adult tissues. The expression of AHox1 is scarcely detected during the course of early development but it increases to a moderate level at the larval stage. After metamorphosis, the level of AHox1 expression increases as development proceeds. In situ hybridization to the juvenile 7 days after metamorphosis showed that the site of AHox1 expression is the epithelium of digestive tract. Among the adult tissues examined, digestive tract, digestive gland and coelomic cells were the major sites of the expression of AHox1. In gonad, body wall muscle and pharyngeal epithelium, the expression of AHox1 is relatively weak. These results suggest that AHox1 is primarily expressed in the tissues of endodermal origin and that the gene expression may be associated with differentiation of the endodermal tissues.

Amino Acid Sequence↗