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Biomedical subjects

H Naora

Publications and source records attributed to H Naora.

At least 73 records · Page 4Linked to original sources
PubMed1982

Clustered genes require extragenic territorial DNA sequences.

This paper is concerned with the basic question as to whether there exists a complex interaction between DNA sequences which have little specific function and functional genes regarding the spatial arrangement of the gene. Since gene clusters are a characteristic and basic feature of gene structure in higher eukaryotes, the size of extragenic DNA sequences surrounding the individual genes of various clustered gene families were compared. The size of the intergenic region, which is composed of the extragenic DNA sequences flanking the 3'-end of one gene and those flanking the 5'-end of the other gene, of the paired genes increases as the genes becomes larger. However, such a gene size-dependent increase is not seen if the total gene size of the paired genes is less than 0.3 kb or greater than 4 kb. The results suggests that a higher eukaryote gene requires extragenic territorial DNA sequences surrounding it, which presumably are necessary to maintain the gene's active functions.

Animals↗
PubMed1981

Nucleotide sequence complementarity between adenovirus 2-coded VA RNA and host cell pre-mRNA. A possible regulatory mechanism of cellular RNA splicing by VA RNA.

Using a computer program, complementary of nucleotide sequences was assessed between adenovirus 2-coded VA RNA and presumptive cellular and viral 'pre-mRNAs'. In this paper, the possibility is considered that the splicing of cellular 'pre-mRNA' can be regulated in such a way that the formation of the proper intramolecular double-stranded hairpin structures, key elements for RNA splicing, is prevented by the binding of VA RNAI or RNAII to the nucleotide sequences around the exon-intron and intron-exon joint sites of cellular 'pre-mRNA' molecules. Complementarity assessment showed that VA RNAI can bind to the joint sites in such a way as to form an omega shape at two separate regions around the joint sites of cellular 'pre-mRNA'. Whereas VA RNAI is not capable of binding to viral hexon 'pre-mRNA' in the same manner as it does to cellular 'pre-mRNA', the binding may occur in a different way. Such differential binding is discussed in relation to the post-transcriptional sequence selection which takes place during the late phase of adenovirus infection.

Base Sequence↗
PubMed1981

Electron microscopic observations of heterogeneous nuclear RNA of chicken reticulocytes.

Secondary structures of annealed, snapped-back and untreated chicken reticulocyte poly(A)-containing nuclear RNA were investigated by electron microscopy. Three shapes of molecules were observed: 'coat'hanger' shaped, loop-bearing and filamentous molecules. The former two shaped molecules consist of a small and large fold-back or loop plus a short hook or tail, corresponding to the poly(A) segment at the apparent middle of the structure. The third shaped molecule, mainly seen after snap-back treatment, possesses a small fold-back structure at one end only. It is suggested that the small and large fold-backs or loops of the molecule represent the 5'- and 3'-terminal hairpin structures, respectively. Two distinct sizes of molecule, small and large, irrespective of molecule shape, were observed.

Animals↗
PubMed1981

A possible regulatory mechanism in RNA processing and its implication for posttranscriptional sequence control during differentiation of cell function.

1. This paper is concerned with the possible molecular mechanism for RNA processing including posttranscriptional sequence control underlying the differentiation of cell functions. 2. It was previously postulated that intramolecular double-stranded hairpin structures present at 5'- and 3'-terminal regions of a 'pre-mRNA' are key elements for RNA splicing [24]. 3. In this paper the possibility is considered that the splicing of 'pre-mRNA' can be regulated in such a way that the formation of the proper double-stranded hairpin structures is prevented by the binding of low-molecular-weight nuclear RNA (LnRNA) to the terminal regions and/or to the nucleotide sequences around the exon-intron and intron-exon joint sites of the 'pre-mRNA' molecules. 4. Complementarity assessment of nucleotide sequences of rat preproinsulin 'pre-mRNA' and rat LnRNA, i.e. Ul, showed that Ul RNA is capable of forming stable double-standard intermolecular structures around the joint sites of preproinsulin 'pre-mRNA' and may prevent the formation of intramolecular double-stranded structures required for RNA splicing. This may imply a regulatory (inhibitory) role for Ul RNA in the processing of 'pre-mRNA'. 5. A possible regulatory role of LnRNA in RNA splicing is discussed in relation to the determination of the mRNA population to be translated in the cytoplasm during differentiation of cell functions.

Animals↗
PubMed1980

Complete nucleotide sequence of a cloned chicken alpha-globin cDNA.

Chicken globin double-stranded cDNA was synthesised from anaemic adult reticulocyte alpha- and beta-globin mRNA and ligated into the Hind III site of pBR322 using synthetic Hind III decamers. Transformation of E. coli x1776 resulted in the production of a number of alpha- and beta-cDNA clones. One of the alpha-type clones (pCG alpha-8) was fully sequenced and found to code for neither alpha A- nor alpha D-globin. Partial sequencing of the other alpha-cDNA clones indicates that they are all of the same type.

Animals↗
PubMed1977

Electron microscopic studies of purified eukaryote messenger RNA.

Rat liver mRNA, hen and rabbit globin messenger RNA (mRNA) were investigated by electron microscopy. No secondary structures were visible in the molecules of these mRNAs under conditions where short secondary structures of other types of RNA, i.e. MS2 phage RNA and 28 S rRNA, were clearly demonstrated. The contour lengths of these mRNAs were also determined by electron microscopy and compared with the sizes estimated by other techniques. The contour lengths of rabbit short and long globin mRNA are 0.1498 +/- 0.0019 and 0.1908 +/- 0.0021 micrometer, respectively. The former is assumed to be globin mRNA for alpha chain and the latter for beta chain. Similarly, hen "alpha" and "beta" globin mRNA have mean lengths of 0.1449 +/- 0.0011 and 0.1891 +/- 0.0017 micrometer, respectively. Hen and rabbit reticulocytes contain 1.8-2.0 times as much mRNA for alpha globin chains as for beta.

Animals↗
PubMed1975

A comparison of the chromatographic properties of various polyadenylate binding materials.

The suitability of various materials for messenger RNA isolation and possible fractionation was examined by comparing the chromatographic behaviour of synthetic poly(riboadenylic acid) [poly(A)] and ribosomal RNA on each suport. The ratios of poly(A) to ribosomal RNA capacities of the various materials under different chromatographic conditions were used to estimate the potential selectivity of the columns for messenger RNA isolation. Using this criterion, benzoylated cellulose and oligo(deoxythymidylate)-cellulose should be the most selective materials of those studied. The elution conditions (temperature or salt gradient) used to obtain bound poly(A) were investigated to determine the optimum conditions for possible messenger RNA fractionation. It is concluded that oligo(deoxythymidylate)-cellulose appears to be the most suitable support of those investigated for messenger RNA isolation and possible fractionation.

Binding Sites↗