RESUMEN
The mutation system has been developed to study the mutagenic properties of modified oligonucleotide analogs. The mutagenic properties of oligonucleotides containing one ribonucleotide have been examined. The presence of a ribonucleotide is shown not to induce any mutations. But when the oligonucleotide induces two marker deletions detached by 6 nucleotides they may be repaired separately, in this case the deletion bordering with the ribonucleotide is predominantly repaired.
Asunto(s)
Reparación del ADN , Replicación del ADN , Mutagénesis Sitio-Dirigida , Oligonucleótidos/genética , Ribonucleótidos/genética , Secuencia de Bases , Datos de Secuencia MolecularRESUMEN
The 2' (3'),5'-diphosphates of cytidine, uridine, adenosine and the trinucleoside diphosphates, such as NpCpC, NpCpU, NpUpC, NpUpU and ApNpC (where N = U, C, A, G), were used to study the substrate specificity of the T4 RNA ligase. The outcome of ligating various phosphate acceptors to a common phosphate donor was governed not only by nucleotide composition but also the nucleotide sequence of a phosphate acceptor. The effect of the changes in a single position of the phosphate acceptor on the efficiency of the intermolecular ligation cannot be defined independently of the other nucleotide residues. For four examined groups of phosphate acceptors and pCp as a donor, four different ranks were obtained (in order of decreasing reactivity): C greater than A greater than greater than U greater than G (for NpCpC); G greater than U approximately equal to A greater than C (NpCpU); A greater than U greater than C greater than G (NpUpC) and A greater than G greater than C greater than U (NpUpU). The yield of ligation products with various phosphate donors and a common phosphate acceptor significantly depends on the donor structure: pyrimidine phosphate donors are more effective than pAp, while pCp is more effective than pUp.
Asunto(s)
Fosfatos/metabolismo , Polinucleótido Ligasas/metabolismo , ARN Ligasa (ATP)/metabolismo , Fagos T/enzimología , Secuencia de Bases , Cromatografía por Intercambio Iónico , Nucleósidos/metabolismo , Especificidad por SustratoRESUMEN
A technique for isolation of RNA-ligase of bacteriophage T4 was proposed. It is mainly based on the using of Soviet materials and sorbents and includes seven purification stages. The technique enables to isolate about 80 000 units of active enzyme from 100 g of E. coli B cells infected with the phage. T4am N82; that makes up 20% of the activity of the cell extract. The obtained preparations of RNA-ligase are homogeneous by the data of electrophoresis and practically, free of endo- and exonuclease admixtures.
Asunto(s)
Polinucleótido Ligasas/aislamiento & purificación , ARN Ligasa (ATP)/aislamiento & purificación , Fagos T/enzimología , Cromatografía de Afinidad , Cromatografía DEAE-Celulosa , Cromatografía en Gel , Electroforesis en Gel de Agar , Electroforesis en Gel de Poliacrilamida , Endonucleasas/aislamiento & purificación , Exonucleasas/aislamiento & purificación , Métodos , ARN Ligasa (ATP)/análisis , Fagos T/aislamiento & purificaciónRESUMEN
Restoration of tyrosinamine transferase (TAT) with cortisol in the rat hepatocytes after the cessation of prolonged (for many days) administration of this hormone was investigated. The effect of the liver regeneration and insulin administration on this process was also studied. In single cortisol administration the TAT activity rose 5-fold; the induction response decreased after 21 days of daily administration. The TAT induction in response to cortisol administration was restored completely only on the 25th--30th day after the cessation of this hormone injection. A three-day insulin administration led to the restoration of TAT induction in response to cortisol administration. The process of the liver regeneration during the first 24 hours after partial hepatectomy induced TAT in the cells of both control animals and those given cortisol for prolonged periods; besides, it aided restoration of the induction response to cortisol administration.