Higher rate of tissue regeneration in polyploid asexual versus diploid sexual freshwater snails

Characterizing phenotypic differences between sexual and asexual organisms is a critical step towards understanding why sexual reproduction is so common. Because asexuals are often polyploid, understanding how ploidy influences phenotype is directly relevant to the study of sex and will provide key insights into the evolution of ploidy-level variation. The well-established association between genome size and cell cycle duration, evidence for a link between genome size and tissue regeneration rate and the growing body of research showing that ploidy influences growth rate and gene expression led us to hypothesize that healing and tissue regeneration might be affected by ploidy-level variation. We evaluated this hypothesis by measuring the rate of regeneration of antenna tissue of Potamopyrgus antipodarum, a New Zealand snail characterized by frequent coexistence between diploid sexuals and polyploid asexuals. Antennae of triploid and presumptive tetraploid asexuals regenerated more rapidly than the antennae of diploid sexuals, but regeneration rate did not differ between triploids and tetraploids. These results suggest either that ploidy elevation has nonlinear positive effects on tissue regeneration and/or that factors associated directly with reproductive mode affect regeneration rate more than ploidy level. The results of this study also indicate that the lower ploidy of sexual P. antipodarum is unlikely to confer advantages associated with more rapid regeneration.     

Design,synthesis and evaluation of novel 2-hydroxypyrrolobenzodiazepine-5,11-dione analogues as potent angiotensin converting enzyme (ACE) inhibitors

A series of novel 10-substituted 2-hydroxypyrrolobenzodiazepine-5,11-diones designed through structure based rational hybridization approach, synthesized by the cyclodehydration of isotonic anhydride with (2S,4R)-4-hydroxypyrrolidine-2-carboxylic acid followed by N-substitution, were evaluated as angiotensin converting enzyme (ACE) inhibitors. Among all the new compounds screened (2R,11aS)-10-((4-bromothiophen-2-yl)methyl)-2-hydroxy-2,3-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-5,11(10H,11aH)dione, 5v (IC₅₀: 0.272 μM) emerged as most active non-carboxylic acid ACE inhibitor with minimal toxicity comparable to clinical drugs Lisinopril, Benazepril and Ramipril. Favorable binding characteristics in docking studies also supported the experimental results.     

The use of modified and non-natural nucleotides provide unique insights into pro-mutagenic replication catalyzed by polymerase eta

This report evaluates the pro-mutagenic behavior of 8-oxo-guanine (8-oxo-G) by quantifying the ability of high-fidelity and specialized DNA polymerases to incorporate natural and modified nucleotides opposite this lesion. Although high-fidelity DNA polymerases such as pol δ and the bacteriophage T4 DNA polymerase replicating 8-oxo-G in an error-prone manner, they display remarkably low efficiencies for TLS compared to normal DNA synthesis. In contrast, pol η shows a combination of high efficiency and low fidelity when replicating 8-oxo-G. These combined properties are consistent with a pro-mutagenic role for pol η when replicating this DNA lesion. Studies using modified nucleotide analogs show that pol η relies heavily on hydrogen-bonding interactions during translesion DNA synthesis. However, nucleobase modifications such as alkylation to the N2 position of guanine significantly increase error-prone synthesis catalyzed by pol η when replicating 8-oxo-G. Molecular modeling studies demonstrate the existence of a hydrophobic pocket in pol η that participates in the increased utilization of certain hydrophobic nucleotides. A model is proposed for enhanced pro-mutagenic replication catalyzed by pol η that couples efficient incorporation of damaged nucleotides opposite oxidized DNA lesions created by reactive oxygen species. The biological implications of this model toward increasing mutagenic events in lung cancer are discussed.