Error-Prone Translesion DNA Synthesis by Escherichia coli DNA Polymerase IV (DinB) on Templates Containing 1,2-dihydro-2-oxoadenine

Escherichia coli DNA polymerase IV (Pol IV) is involved in bypass replication of damaged bases in DNA. Reactive oxygen species (ROS) are generated continuously during normal metabolism and as a result of exogenous stress such as ionizing radiation. ROS induce various kinds of base damage in DNA. It is important to examine whether Pol IV is able to bypass oxidatively damaged bases. In this study, recombinant Pol IV was incubated with oligonucleotides containing thymine glycol (dTg), 5-formyluracil (5-fodU), 5-hydroxymethyluracil (5-hmdU), 7,8-dihydro-8-oxoguanine (8-oxodG) and 1,2-dihydro-2-oxoadenine (2-oxodA). Primer extension assays revealed that Pol IV preferred to insert dATP opposite 5-fodU and 5-hmdU, while it inefficiently inserted nucleotides opposite dTg. Pol IV inserted dCTP and dATP opposite 8-oxodG, while the ability was low. It inserted dCTP more effectively than dTTP opposite 2-oxodA. Pol IV's ability to bypass these lesions decreased in the order: 2-oxodA > 5-fodU~5-hmdU > 8-oxodG > dTg. The fact that Pol IV preferred to insert dCTP opposite 2-oxodA suggests the mutagenic potential of 2-oxodA leading to A:T→G:C transitions. Hydrogen peroxide caused an ~2-fold increase in A:T→G:C mutations in E. coli, while the increase was significantly greater in E. coli overexpressing Pol IV. These results indicate that Pol IV may be involved in ROS-enhanced A:T→G:C mutations

Development and prevention of advanced diabetic nephropathy in RAGE-overexpressing mice

金沢大学医薬保健研究域医学系Vascular complications arising from multiple environmental and genetic factors are responsible for many of the disabilities and short life expectancy associated with diabetes mellitus. Here we provide the first direct in vivo evidence that interactions between advanced glycation end products (AGEs; nonenzymatically glycosylated protein derivatives formed during prolonged hyperglycemic exposure) and their receptor, RAGE, lead to diabetic vascular derangement. We created transgenic mice that overexpress human RAGE in vascular cells and crossbred them with another transgenic line that develops insulin-dependent diabetes shortly after birth. The resultant double transgenic mice exhibited increased hemoglobin A1c and serum AGE levels, as did the diabetic controls. The double transgenic mice demonstrated enlargement of the kidney, glomerular hypertrophy, increased albuminuria, mesangial expansion, advanced glomerulosclerosis, and increased serum creatinine compared with diabetic littermates lacking the RAGE transgene. To our knowledge, the development of this double transgenic mouse provides the first animal model that exhibits the renal changes seen in humans. Furthermore, the phenotypes of advanced diabetic nephropathy were prevented by administering an AGE inhibitor, (±)-2-isopropylidenehydrazono-4-oxo-thiazolidin-5-ylacetanilide (OPB-9195), thus establishing the AGE-RAGE system as a promising target for overcoming this aspect of diabetic pathogenesis

The role of AGE-Rage system in the development of diabetic nephropathy in vivo

金沢大学大学院医学部医学系研究科Vascular complications are what eventually threaten the lives of diabetic patients. Here we show direct in vivo evidence that the interaction between advanced glycation end products (AGE), the formation of which is accelerated during prolonged hyperglycemic exposure, and a cell surface receptor for AGE (RAGE) is the major cause of such complications. We created transgenic mice that overexpress human RAGE in vascular cells and crossbred them with another transgenic line which develops insulin-dependent diabetes early after birth. The resultant double transgenic mice exhibited accelerated kidney changes compared with single transgenic littermates, and the nephropathy was ameliorated by an inhibitor of AGE formation. The AGE–RAGE system will thus be a promising target for overcoming diabetic complications

Trinitrophenyl derivatives bind differently from parent adenine nucleotides to Ca2+-ATPase in the absence of Ca2+

Trinitrophenyl derivatives of adenine nucleotides are widely used for probing ATP-binding sites. Here we describe crystal structures of Ca2+-ATPase, a representative P-type ATPase, in the absence of Ca2+ with bound ATP, trinitrophenyl-ATP, -ADP, and -AMP at better than 2.4-Å resolution, stabilized with thapsigargin, a potent inhibitor. These crystal structures show that the binding mode of the trinitrophenyl derivatives is distinctly different from the parent adenine nucleotides. The adenine binding pocket in the nucleotide binding domain of Ca2+-ATPase is now occupied by the trinitrophenyl group, and the side chains of two arginines sandwich the adenine ring, accounting for the much higher affinities of the trinitrophenyl derivatives. Trinitrophenyl nucleotides exhibit a pronounced fluorescence in the E2P ground state but not in the other E2 states. Crystal structures of the E2P and E2 ∼ P analogues of Ca2+-ATPase with bound trinitrophenyl-AMP show that different arrangements of the three cytoplasmic domains alter the orientation and water accessibility of the trinitrophenyl group, explaining the origin of “superfluorescence.” Thus, the crystal structures demonstrate that ATP and its derivatives are highly adaptable to a wide range of site topologies stabilized by a variety of interactions

Development and prevention of advanced diabetic nephropathy in RAGE-overexpressing mice

Vascular complications arising from multiple environmental and genetic factors are responsible for many of the disabilities and short life expectancy associated with diabetes mellitus. Here we provide the first direct in vivo evidence that interactions between advanced glycation end products (AGEs; nonenzymatically glycosylated protein derivatives formed during prolonged hyperglycemic exposure) and their receptor, RAGE, lead to diabetic vascular derangement. We created transgenic mice that overexpress human RAGE in vascular cells and crossbred them with another transgenic line that develops insulin-dependent diabetes shortly after birth. The resultant double transgenic mice exhibited increased hemoglobin A(1c) and serum AGE levels, as did the diabetic controls. The double transgenic mice demonstrated enlargement of the kidney, glomerular hypertrophy, increased albuminuria, mesangial expansion, advanced glomerulosclerosis, and increased serum creatinine compared with diabetic littermates lacking the RAGE transgene. To our knowledge, the development of this double transgenic mouse provides the first animal model that exhibits the renal changes seen in humans. Furthermore, the phenotypes of advanced diabetic nephropathy were prevented by administering an AGE inhibitor, (±)-2-isopropylidenehydrazono-4-oxo-thiazolidin-5-ylacetanilide (OPB-9195), thus establishing the AGE-RAGE system as a promising target for overcoming this aspect of diabetic pathogenesis