The E. coli Protein YbgL: A Novel DNA Repair Enzyme?

Cr(V) is a carcinogen that oxidizes guanine aggressively to form spiroiminodihydantion (Sp) and guanidinohydantoin (Gh), both of which contain an unusual hydantoin moiety that cause G→T transversion mutations at a high rate. Endonuclease VIII (nei) can recognize and excise these oxidation products from DNA and is translated as one of five protein products of the Nei operon in Escherichia coli (E. coli). However, the functions of the other four proteins remain unknown. To address this gap in knowledge, we focused on one of the four that immediately precedes nei, the ybgL protein. Previous work by our group has suggested a role for ybgL in vitro. In the current study, we attempt to characterize the role of ybgL by oxidizing a synthetic oligo with Cr(V) and reacting the oxidized oligo with ybgL in the presence of different potential cofactors. Due to the presence of hydantoin moieties within the DNA, we modeled the ybgL protein to the Hydantoinase B class of enzymes, which recognize the hydantoin moiety. This study will attempt to elucidate the role of an uncharacterized protein in excising oxidation lesions caused by chromium toxicity

Guanine and 7,8-dihydro-8-oxo-guanine-specific oxidation in DNA by chromium(V).

The hexavalent oxidation state of chromium [Cr(VI)] is a well-established human carcinogen, although the mechanism of cancer induction is currently unknown. Intracellular reduction of Cr(VI) forms Cr(V), which is thought to play a fundamental role in the mechanism of DNA damage by this carcinogen. Two separate pathways of DNA damage, an oxidative pathway and a metal-binding pathway, have been proposed to account for the lesions observed in cell systems. We have used a model Cr(V) complex, N,N-ethylenebis(salicylidene-animato)oxochromium(V) [Cr(V)-Salen], to investigate the oxidative pathway of DNA damage and to elucidate the lesions generated from this oxidation process. Reaction of Cr(V)-Salen with synthetic oligonucleotides produced guanine-specific lesions that were not 8-oxo-2'-deoxyguanosine, based on the inability of iridium(IV) to further oxidize these sites. Oxidation products were identified using a 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxo-G) containing oligonucleotide to increase the yields of product for identification by electrospray ionization mass spectrometry. The guanine-based lesions observed by mass spectrometry corresponded to the lesions guanidinohydantoin and spiroiminodihydantoin. The effects of these Cr(V)-Salen-induced lesions on DNA replication fidelity was assayed using a polymerase-based misincorporation assay. These lesions produced G --> T transversion mutations and polymerase stops at levels greater than those observed for 8-oxo-G. These data suggest a model by which chromate can cause DNA damage leading to mutations and cancer

The Subcomponents of Affect Scale (SAS): Validating a Widely Used Affect Scale

Objective There is a need for a brief affect scale that also encompasses different components of affect relevant for researchers interested in physiological and health outcomes. The Subcomponents of Affect Scale (SAS) meets this need. This 18-item scale has nine positive and nine negative affect items encompassing six subscales (calm, well-being, vigour, depression, anxiety, anger). Previous research using the SAS has demonstrated its predictive validity, but no work has tested its subscale structure or longitudinal validity. Design Data from the Common Cold Project in which individuals (N = 610) completed the SAS over the course of seven days were used. Results Confirmatory factor analysis demonstrated the reliability of the subscale structure of the SAS across seven days (positive affect subscale structure: CFIs ≥ 0.98; negative affect subscale structure: CFIs ≥ 0.94 with day 6 CFI = 0.91) and tests of factorial invariance showed the scale is valid to use over time. Conclusions These results confirm the psychometric validity of the subscale structure of the SAS and imply that the subscales can be used longitudinally, allowing for its use in health research as well as non-health research that can benefit from its subscale structure and longitudinal capabilities