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At least 361 records · Page 20Linked to original sources
PubMed2001

Role of distal zinc finger of nucleocapsid protein in genomic RNA dimerization of human immunodeficiency virus type 1; no role for the palindrome crowning the R-U5 hairpin.

Genomic RNA isolated from HIV-1 variously mutated in nucleocapsid protein (NC) was characterized by nondenaturing gel electrophoresis. Mutations in the C-terminal, the N-terminal, and the linker regions had no effect on genomic RNA dimerization [they are R7R10K11S, P31L, R32G, S3(32-34), and K59L], while a C36S/C39S mutation in the distal zinc knuckle (Cys-His box or zinc finger) inhibited genome dimerization as much as disrupting the kissing-loop domain. The four mutations which inhibited tRNA(Lys3) genomic placement (i.e., the in vivo placement of tRNA(Lys3) on the primer binding site) had no effect on genome dimerization. Among five mutations which inhibited genome packaging, four had no effect on genome dimerization. Thus the N-terminal and linker regions of NC control genome packaging/tRNA(Lys3) placement (two processes which do not require mature NC) but have little influence on genome dimerization and 2-base extension of tRNA(Lys3) (two processes which are likely to require mature NC). It has been suggested, based on electron microscopy, that the AAGCUU82 palindrome crowning the R-U5 hairpin stimulates genomic RNA dimerization. To test this hypothesis, we deleted AGCU81 from wild-type viruses and from viruses bearing a disrupted kissing-loop hairpin or kissing-loop domain; in another mutant, we duplicated AGCU81. The loss of AGCU81 reduced dimerization by 2.5 +/- 4%; its duplication increased it by 3 +/- 6%. Dissociation temperature was left unchanged. We reach two conclusions. First, the palindrome crowning the R-U5 hairpin has no impact on HIV-1 genome dimerization. Second, genomic RNA dimerization is differentially influenced by NC sequence: it is Zn finger dependent but independent of the basic nature of the N-terminal and linker subdomains. We propose that the NC regions implicated in 2-base extension of tRNA(Lys3) are required for a second (maturation) step of tRNA placement. Genome dimerization and mature tRNA placement would then become two RNA-RNA interactions sharing similar NC sequence requirements.

Amino Acid Sequence↗
PubMed1990

Role of calf thymus DNA-topoisomerase I phosphorylation on relaxation activity expression and on DNA-protein interaction. Role of DNA-topoisomerase I phosphorylation.

Calf thymus DNA-Topoisomerase I activity was found to be altered by changing in phosphorylation: it was completely inhibited upon dephosphorylation by alkaline phosphatase, but incubation with N II protein kinase and ATP restored the relaxation activity to a level higher than that observed prior to dephosphorylation. The calf thymus Topoisomerase I-mediated DNA cleavage, induced by camptothecin, also proved to be inhibited by dephosphorylation, which, apparently, stabilizes the initial enzyme-substrate complex. We conclude that: the native protein is partially phosphorylated, the phosphorylation involvement is essential for the activity expression and also for DNA-protein interaction, changes in the degree of phosphorylation might be involved in the regulation of DNA processing; that evokes some properties of chromatinic peptide models, which bind DNA only when phosphorylated and leads to the assumption that they represent the minimum functional substrate for N II protein kinase.

Animals↗
PubMed1987

Adipose tissue development: the role of precursor cells and adipogenic factors. Part I: Adipose tissue development and the role of precursor cells.

Obesity is regarded as a heterogeneous syndrome, which may appear in different forms. Various causes have been found to contribute to its pathogenesis. During recent years investigations of adipose tissue cellularity and its dynamic changes have gained growing interest. An important progress was the discovery of adipose tissue precursor cells. These cells have not yet been precisely identified by morphological and biochemical methods in intact tissue. However, due to methodological developments such precursor cells can be cultured both as primary cultures and as established cell lines. These culture systems have proven to be valuable models for the study of the processes involved in the formation of new fat cells.

Adipose Tissue↗
PubMed1980

Evidence that endogenous vasopressin plays a protective role in circulatory shock. Role for reticuloendothelial system using Brattleboro rats.

Experiments performed on male Wistar, Long Evans and Brattleboro rats indicate that the latter strain of animals, lacking vasopressin in their posterior pituitaries, are extremely sensitive to hemorrhagic and bowel ischemic shock. Mild forms of both hemorrhagic and bowel ischemic shock, as produced in Wistar or Long Evans rats, results in marked hypotension, hemoconcentration and blockade of the reticuloendothelial system (RES) in Brattleboro animals of similar sex, age and weight. These direct findings indicate that release of endogenous vasopressin in shock syndromes may be critical in maintenance of circulatory homeostasis and RES function.

Animals↗
PubMed1994

Role of proline in the imprinting developed by dipeptides--in Tetrahymena. Possible role in hormone evolution.

The effects of proline and serine dipeptides containing phenylalanine, alanine and leucine on the behaviour of receptors of Tetrahymena were investigated. Only proline-containing dipeptides were able to develop positive imprinting, and the activity depended on which other amino acid was present in the dipeptide. In contrast to the positive imprinting effect of the dipeptides Pro-Phe and Pro-Ala, the dipeptide Pro-Pro and Pro-Leu caused negative imprinting. Serine dipeptides produced negative imprinting in all cases. The possible importance of proline in the evolution of hormone specificity is discussed.

Animals↗
PubMed2005

The role of intramolecular hydrogen bonding on nucleobase acidification following metal coordination: possible implications of an "indirect" role of metals in acid-base catalysis of nucleic acids.

The acidifying effect of Pt(II) on nucleobase -NH and -NH2 groups depends both on the site of metal coordination and on the efficiency of stabilization of the deprotonated nucleobase via intracomplex hydrogen bonding. Weakly acidic nucleobase protons with pK (a) values between 9 and 17 can be acidified by a single Pt(II) to have pK (a) values which are well within the physiological pH range. This could open the possibility of an acid-base catalysis occurring at pH 7, with the metal-nucleobase entity functioning either as an acid or a base. Examples of Pt(II) complexes studied here include, among others, mixed nucleobase systems of 1-methylcytosine and 1,9-dimethyladenine as well as a complex of the rare iminooxo tautomer of 1-methylcytosine having the metal bonded at N4.

Catalysis↗