Dynamic removal of replication protein A by Dna2 facilitates primer cleavage during Okazaki fragment processing in Saccharomyces cerevisiae

Eukaryotic Okazaki fragments are initiated by an RNA/DNA primer, which is removed before the fragments are joined. Polymerase d displaces the primer into a flap for processing. Dna2 nuclease/helicase and flap endonuclease 1 (FEN1) are proposed to cleave the flap. The single-stranded DNA binding protein, replication protein A (RPA), governs cleavage activity. Flap-bound RPA inhibits FEN1. This necessitates cleavage by Dna2, which is stimulated by RPA. FEN1 then cuts the remaining RPA-free flap to create a nick for ligation. Cleavage by Dna2 requires that it enter the 5'-end and track down the flap. Since Dna2 cleaves the RPA-bound flap, we investigated the mechanism by which Dna2 accesses the protein-coated flap for cleavage. Using a nuclease-defective Dna2 mutant, we showed that just binding of Dna2 dissociates the flap-bound RPA. Facile dissociation is specific to substrates with a genuine flap, and will not occur with an RPA-coated single strand. We also compared the cleavage patterns of Dna2 with and without RPA to better define RPA stimulation of Dna2. Stimulation derived from removal of DNA folding in the flap. Apparently, coordinated with its dissociation, RPA relinquishes the flap to Dna2 for tracking in a way that does not allow flap structure to reform. We also found that RPA strand melting activity promotes excessive flap elongation, but it is suppressed by Dna2-promoted RPA dissociation. Overall, results indicate that Dna2 and RPA coordinate their functions for efficient flap cleavage and preparation for FEN1

The future shape of AUSTUDY: Practical and policy implications of the recent proposed changes

ABSTUDY, the Aboriginal Study Assistance Scheme, is one of the most contentious special programs in Indigenous affairs. In May 1997 the Howard Government announced a number of changes to ABSTUDY, including substantial reductions in funding by fiscal year 2000/01; these changes are to go into effect from 1 January 1998. This paper has been prepared to provide an overview of the announced changes and speculate on some of the possible outcomes. Nationally, the number of ABSTUDY participants has fluctuated only marginally over the past several years, increasing from 40,813 in 1988 to 48,769 in 1996. Expenditure on ABSTUDY grew from $81.1 million to$121.6 million during this same period. Calculated in 1988/89 dollars, expenditure between 1988 and 1996 increased 12 per cent while the Consumer Price Index increased by 34 per cent. As part of the announced ABSTUDY changes, the Government has projected reductions in outlays of $38.7 million by fiscal year 2000ö01. Even with low levels of inflation, the proposed cuts to ABSTUDY represent a significant drop in Government expenditure. Overview of the announced changes Effective 1 January 1998, ABSTUDY benefits will be subject to a range of additional restrictions: Living Allowance: where ABSTUDY had employed a 'sudden death' cut off, from 1998 the cut-off will be replaced by an abatement scheme with a threshold well below current cut-off levels. Additional Incidentals Allowance: there is currently no limit to the allowance (except for Masters and PhD students for whom a$2,000 limit applies). From 1998, the allowance will be capped at $2,000 for all students. School Fees Allowance: beginning in 1998, the applicant (or the partner of the applicant) must qualify for Government assistance to be eligible for this allowance. Fares Allowance: travel interstate for certificate or enabling courses will no longer be allowed; compassionate travel will be limited to two return trips per year; travel home will be restricted where the student has brought dependent family members to the place of study; and fare assistance to attend a graduation ceremony will be restricted. Eligibility and awards: from 1998, students will be eligible for ABSTUDY assistance for only one undergraduate and two postgraduate courses. Away From Base Assistance: from 1998, this assistance will be restricted to a maximum of two return trips of no more than four weeks duration per year. Courses composed wholly or substantially of Away From Base components will no longer be eligible for coverage under ABSTUDY. Considerations for the future It is impossible to project the full impact of the announced changes at the present time; necessary data on current participants are not accessible and figures for Indigenous enrolments will not be available until well after the changes have gone into effect. Some predictions are possible, however. For example, while DEETYA staff have estimated that 550 students would be affected by the changes to the Away From Base component of ABSTUDY, research undertaken for this paper indicates that as many as 868 students in eight universities across 11 campuses could be affected immediately by these changes in the State of New South Wales alone. The authors conclude that there is a serious disjunction between the Government's announced commitment to improving educational outcomes for Indigenous Australians and reductions in a program developed specifically to improve the educational and employment prospects of a socially and economically disadvantaged segment of the population. From a policy perspective, it is puzzling that plans to pare back a program that many would argue has been instrumental in increasing Indigenous access and participation in education were announced before the Government's formal review of the program had been started, let alone completed. Further, the lack of detail on cost savings and the absence of any educational rationale leaves a distinct impression that this is an ideological and politically-driven exercise rather than one based on sound educational or economic principles. The issues are not merely political ones. If Indigenous access to education is impeded, participation will decline. If participation declines, employment opportunities will likely decline as well. If employment opportunities decline the social welfare bill, and associated negative externalities for Australia, will increase

Respiration Rates of Two Midge Species at Different Temperatures

Respiration values for Chironomus n. sp. ranged from 0.11 mm³ O₂ /mg/hr at 5C to 0.44 mm³ O₂. /gm/hr at 25C. The range for Chaoborus punctipennis was from 0.15 mm³ O₂ /mg/hr at 5C to 0.56 mm³ O₂ /mg/hr at 25C. These low respiratory rates allow the two species to withstand low oxygen tensions for extended periods of time. Reflecting this ability, both species attained their greatest numerical and biomass values in the profundal regions of three strip-mine lakes whose lower waters become oxygen depleted during thermal stratification

Traits controlling body size in copepods: separating general constraints from species-specific strategies

A new synthesis of laboratory measurements of food-saturated development and growth across diverse copepod taxa was conducted in a theoretical framework that distinguishes general allometric constraints on copepod physiology from contingent strategies that correlate with size for other reasons. After temperature correction, the allometry of growth rate is inconsistent between the ontogeny of Calanus spp., where it follows the classic -0.3 power-law scaling, and a broader spectrum of adult size Wa (0.3 to 2000 µg C, Oithona spp. to Neocalanus spp.), across which the classic scaling appears to represent only an upper limit. Over the full size spectrum, after temperature correction, a growth rate g0relative to the -0.3 power law correlates with adult size better than does relative (temperature-corrected) development rate u0; in contrast, at a finer scale of diversity (among Calanus spp., or among large (\u3e50 µg C) calanoids in general), u0 is the better correlate with adult size and the effect of g0 is insignificant. Across all these scales, the ratio of relative growth and development rates g0/u0 is a better predictor of adult size than g0 or u0 alone, consistent with a simple model of individual growth

2014 Dahlberg Award Winner: The effects of dietary toughness on occlusopalatal variation in savanna baboons

This study investigates the relationship between dietary toughness and craniofacial variation in two groups of savanna baboons. Standard craniofacial and malocclusion data were collected from a captive, soft-diet experiment group (n=24) and a sample of wild-captured baboons, raised on tougher, natural foods (n=19). We tested the hypothesis that in the absence of normal masticatory stress experienced during the consumption of wild foods, the captive baboons would exhibit higher levels of facial and dental structural irregularities. Principal component analysis indicates separation of the two samples. The soft-diet sample exhibits significantly shorter palates, greater variability in palate position, and higher frequencies of occlusal irregularities that correlate with the shorter palates. Results offer further support that long-term dietary chewing stresses have a measurable effect on adult craniofacial variation

The use of data in decision making for school-based social work

Industries are increasingly taking advantage of the access provided in the digital age to use data to inform business and practice-based decision making. The profession of social work has recently called for social workers to become more data-driven, through its Grand Challenge to leverage technology such as data-driven decision making for social good. School-Based Social Workers, who often work in educational contexts that demand they collect and use data are being asked to figure out ways to engage data to help promote evidence-informed practices and process level changes. Using a scoping review, this article looks at the state of the current literature on how this process is evolving. This information can help set the stage for a framework for the systematic application of data in social work settings