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S Maines

Publications and source records attributed to S Maines.

7 recordsLinked to original sources
PubMed1998

Novel mutations in the RAD3 and SSL1 genes perturb genome stability by stimulating recombination between short repeats in Saccharomyces cerevisiae.

Maintaining genome stability requires that recombination between repetitive sequences be avoided. Because short, repetitive sequences are the most abundant, recombination between sequences that are below a certain length are selectively restricted. Novel alleles of the RAD3 and SSL1 genes, which code for components of a basal transcription and UV-damage-repair complex in Saccharomyces cerevisiae, have been found to stimulate recombination between short, repeated sequences. In double mutants, these effects are suppressed, indicating that the RAD3 and SSL1 gene products work together in influencing genome stability. Genetic analysis indicates that this function is independent of UV-damage repair and mutation avoidance, supporting the notion that RAD3 and SSL1 together play a novel role in the maintenance of genome integrity.

Adenosine Triphosphatases↗
PubMed1995

The essential helicase gene RAD3 suppresses short-sequence recombination in Saccharomyces cerevisiae.

We have isolated an allele of the essential DNA repair and transcription gene RAD3 that relaxes the restriction against recombination between short DNA sequences in Saccharomyces cerevisiae. Double-strand break repair and gene replacement events requiring recombination between short identical or mismatched sequences were stimulated in the rad3-G595R mutant cells. We also observed an increase in the physical stability of double-strand breaks in the rad3-G595R mutant cells. These results suggest that the RAD3 gene suppresses recombination involving short homologous sequences by promoting the degradation of the ends of broken DNA molecules.

Adenosine Triphosphatases↗
PubMed1991

Loss of response to thyroid hormone in developing nervous tissue correlates with enhanced synthesis of a 25-kilodalton stress protein.

Directly following transfer to in vitro conditions, lumbar dorsal root ganglia (DRG) from triiodothyronine (T3)-treated premetamorphic tadpoles showed an approximately three fold increase in incorporation of bath-applied radiolabeled amino acid relative to DRG from vehicle-treated tadpoles. By contrast, at 1 h after transfer, no increased incorporation was detected. At this time, examination of in-vitro-synthesized [35S]proteins by two-dimensional gel electrophoresis revealed a selective enhancement of a slightly acidic 25-kilodalton (kD) polypeptide. Addition of 1 M glycerol to the incubation medium prevented the enhanced synthesis of the low-molecular-weight polypeptide and preserved the T3 response. When DRG were exposed in situ, the T3 response - monitored following intraganglionic injection of [35S]methionine-was detected after 2 h, but not after 4 h. Four hours were also the earliest time at which an elevated level of the 25-kD polypeptide was observed. The correlation between loss of hormonal responsiveness and appearance of a putative stress protein is of general importance as a cautionary note for in vitro studies of endocrine effects on developing tissues.

Animals↗
PubMed1989

Sensory ganglia from tadpoles but not adult bullfrogs synthesize heat shock-like proteins in vitro at non-heat shock temperature.

Lumbar dorsal root ganglia (DRG) from premetamorphic bullfrog tadpoles showed a selectively enhanced accumulation of two radiolabeled proteins when incubated in vitro at 22 degrees C for longer than 1 hr. During the first hour in vitro or after in vivo labeling, these polypeptides--of 25 and 68 kD molecular mass and slightly acidic isoelectric point--were detected in the DRG only at relatively low levels. Accumulation of the 25 kD species increased in lumbar DRG from tadpoles of all metamorphic stages but waned at stage XXV (completion of metamorphosis) and was absent from DRG of adult bullfrogs. In contrast, increased levels of the 68 kD species were detected only at premetamorphic stages. Tail DRG from premetamorphic tadpoles did not increase their synthesis of either polypeptide in vitro, which is consistent with the above findings because sensory neurons in tail DRG, but not in lumbar DRG, are mature at this developmental stage. Although the molecular sizes of the two polypeptides led us initially to consider them as heat shock-like proteins, only the 68 kD species was further increased (by approximately 100-fold) when premetamorphic lumbar DRG were incubated at 37 degrees C. The 25 kD species, which was the predominant protein induced at 22 degrees C, showed no further increase in response to hyperthermia. The enhanced in vitro synthesis of these polypeptides at control temperature (22 degrees C) is an example of cellular stress responses that may occur not as a consequence of elevated temperature or exogenous chemical agents, but as a result of transplantation-associated trauma. This phenomenon also represents an example of a cellular stress response that is "outgrown" during development.

Aging↗
PubMed1988

Synthesis, biological activity and conformational analysis of cyclic GRF analogs.

A novel cyclic GRF analog, cyclo(Asp8-Lys12)-[Asp8,Ala15]-GRF(1-29)-NH2, i.e. cyclo8,12[Asp8,Ala15]-GRF(1-29)-NH2, was synthesized by the solid phase procedure and found to retain significant biological activity. Solid phase cyclization of Asp8 to Lys12 proceeded rapidly (approximately 2 h) using the BOP reagent. Substitution of Ala2 with D-Ala2 and/or NH2-terminal replacement (desNH2-Tyr1 or N-MeTyr1) in the cyclo8,12[Asp8,Ala15]-GRF(1-29)-NH2 system resulted in highly potent analogs that were also active in vivo. Conformational analysis (circular dichroism and molecular dynamics calculations based on NOE-derived distance constraints) demonstrated that cyclo8,12[Asp8,Ala15]-GRF(1-29)-NH2 contains a long alpha-helical segment even in aqueous solution. A series of cyclo8,12 stereoisomers containing D-Asp8 and/or D-Lys12 were prepared and also found to be highly potent and to retain significant alpha-helical conformation. The high biological activity of cyclo8,12[N-MeTyr1,D-Ala2,Asp8,Ala15]-GRF(1-29)- NH2 may be explained on the basis of retention of a preferred bioactive conformation.

Animals↗
PubMed1988

Hepatic cytochrome P-450j induction in the spontaneously diabetic BB rat.

Hepatic microsomal cytochrome P-450j has been studied using the male spontaneously diabetic BB rat as a model for insulin-dependent diabetes. This approach avoids any direct hepatotoxic effects from chemical diabetogenic agents. Both diabetic rats maintained on insulin and nondiabetic littermates were used as controls. Levels of cytochrome P-450j were increased approximately 3-fold in the diabetics 4 days after the cessation of insulin therapy. In addition, cytochrome P-450j-catalyzed enzymatic activities, aniline hydroxylation, and N-nitrosodimethylamine N-demethylation were increased by the diabetic state at this same time period. Cytochrome P-450f remained at control levels in all groups of animals. In order to test the hypothesis that ketone bodies are involved in the increase in cytochrome P-450j in the diabetic state, plasma beta-hydroxybutyrate levels were monitored. Hepatic aniline hydroxylation, N-nitrosodimethylamine N-demethylation, and cytochrome P-450j levels in individual animals were found to correlate with plasma beta-hydroxybutyrate levels (r = 0.59-0.71 p less than 0.001). In contrast, no significant correlation between levels of cytochrome P-450j and plasma glucose, insulin, or cholesterol was observed in individual animals (r = 0.07-0.23, p greater than 0.4). We conclude that cytochrome P-450j is induced in the livers of spontaneously diabetic rats, and that this induction may be associated directly or indirectly with elevated plasma ketone levels.

3-Hydroxybutyric Acid↗