PubMed Health⌕ Search

Biomedical subjects

R Kikuno

Publications and source records attributed to R Kikuno.

43 records · Page 3Linked to original sources
PubMed1983

Complete nucleotide sequence of the human corticotropin-beta-lipotropin precursor gene.

The nucleotide sequence of an 8658-base-pair human genomic DNA segment containing the entire corticotropin-beta-lipotropin precursor gene has been determined, and some sequence features of the gene and its flanking regions have been analysed. The gene is composed of 7665 base pairs including two introns of 3708 and 2886 base pairs. Comparison of the 5'-flanking sequences of the human, bovine and mouse corticotropin-beta-lipotropin precursor genes reveals the presence of a highly conserved region, which contains sequences of 14-15 base pairs homologous with sequences located upstream of the mRNA start site of other glucocorticoid-regulated genes.

Adrenocorticotropic Hormone↗
PubMed1982

A pseudogene cluster in the leader region of the Euglena chloroplast 16S-23S rRNA genes.

The nucleotide sequence of a region (leader region) preceding the 5'-end of 16S-23S rRNA gene region of Euglena gracilis chloroplast DNA was compared with the homologous sequences that code for the 16S-23S rRNA operons of Euglena and E. coli. The leader region shows close homology in sequence to the 16S-23S rRNA gene region of Euglena (Orozco et al. (1980) J. Biol.Chem. 255, 10997-11003) as well as to the rrnD operon of E. coli, suggesting that it was derived from the 16S-23S rRNA gene region by gene duplication. It was shown that the leader region had accumulated nucleotide substitutions at an extremely rapid rate in its entirety, similar to the rate of tRNAIle pseudogene identified in the leader region. In addition, the leader region shows an unique base content which is quite distinct from those of 16S-23S rRNA gene regions of Euglena and E. coli, but again is similar to that of the tRNAIle pseudogene. The above two results strongly suggest that the leader region contains a pseudogene cluster which was derived from a gene cluster coding for the functional 16S-23S rRNA operon possibly by imperfect duplication during evolution of Euglena chloroplast DNA.

Base Sequence↗
PubMedDate not supplied

Possible role of the first intron of c-H-ras in gene expression: anti-cancer elements in oncogenes.

When members of ras gene family, which encode structurally related proteins of approximately 21,000 daltons (p21), are activated by either structural mutations or enhanced promoter activities, immortalized mammalian cells can be transformed into malignant forms. The ras genes are classified as "housekeeping genes" which express relatively constantly at low levels in all tissues and throughout all developmental stages. It is therefore important to understand how regulatory, cis-acting in particular, elements of the genes control their expression. We have previously reported that the principal promoter, 51 bp long or less, located around 1370 bp upstream from the first coding ATG, plays the most important role for expression, though there seem to be residual promoter activities further downstream as well. The most upstream mRNA start site is located at the 3'-end of the principal promoter, which lies directly adjacent to the homologous sequence between human and rat c-H-ras 5'-flanking regions. It is therefore proposed that the c-H-ras gene may have a dispersed promoter in which the principal promoter and subpromoters may be distributed. On the other hand, the first intron region seems to contain two sets of positive and negative elements which appear to have, respectively, a positive and negative influence on the efficiency of focus formation with the activated c-H-ras oncogene. From testing done in our laboratory, it was further revealed that these cis-acting elements in the intron affect c-H-ras gene expression at the post-transcriptional level. The middle part of the first intron was in fact shown unusually conserved between human and rat DNA sequences. Moreover, computer analyses revealed that the intron sequences of various oncogenes (both human and rodent sequences available from GenBank DNA sequence data-bank) such as ras, fos, c-myc, N-myc and int-1, are in general significantly more highly conserved when compared with sequences of non-oncogene introns. The significance of this oncogene-related conserved sequence is discussed and the proposal is made that it may function as an "anti-cancer element" or "safety valve" against gene truncation/translocational activation of oncogenes.

Base Sequence↗