A scoping review to identify and describe the characteristics of theories, models and frameworks of health research partnerships.

BACKGROUND: Engaging users of health research, namely knowledge users, as partners in the research process may to lead to evidence that is more relevant to the users. This may optimize the uptake of evidence in healthcare practice, resulting in improved health outcomes or more efficient healthcare systems. However, barriers to involving knowledge users in the research process exist. Theories, models and frameworks may help guide the process of involving knowledge users and address barriers to engaging with knowledge users in research; however, there is little evidence identifying or describing the theories, models and frameworks of health research partnerships. OBJECTIVES: Identify and describe theories, models and frameworks of health research partnerships. Report on concepts of knowledge user engagement represented in identified theories, models and frameworks. METHODS: We conducted a scoping review. Database (MEDLINE, Embase, CINAHL, PCORI) and ancestry and snowball searches were utilized. Included articles were written in English, published between January 2005 and June 2021, specific to health, a research partnership, and referred to a theory, model or framework. No critical appraisal was conducted. We developed a coding framework to extract details related to the publication (e.g. country, year) and theory, model or framework (e.g. intended users, theoretical underpinning, methodology, methods of development, purpose, concepts of knowledge user engagement). One reviewer conducted data extraction. Descriptive statistics and narrative synthesis were utilized to report the results. RESULTS: We identified 21 874 articles in screening. Thirty-nine models or frameworks were included in data analysis, but no theory. Two models or frameworks (5%) were underpinned by theory. Literature review was the method (n = 11, 28%) most frequently used to develop a model or framework. Guiding or managing a partnership was the most frequently reported purpose of the model/framework (n = 14, 36%). The most represented concept of knowledge user engagement was principles/values (n = 36, 92%). CONCLUSIONS: The models and frameworks identified could be utilized by researchers and knowledge users to inform aspects of a health research partnership, such as guidance or implementation of a partnership. Future research evaluating the quality and applicability of the models and frameworks is necessary to help partners decide which model or framework to implement.

Siblings of children with complex care needs: their perspectives and experiences of participating in everyday life.

BACKGROUND: Participating in everyday life is essential to the healthy development and emotional well-being of children. However, little is known about siblings of children with complex care needs (CCN), and their perspectives and experiences of participating in everyday life. The aim of this paper is to present research findings that add to our understanding of how siblings of children with CCN view and experience participation in everyday life. METHODS: To arrive at a detailed and accurate understanding of the siblings' perspectives and experiences, we used the qualitative research design of ethnography. Sixteen siblings (seven brothers, nine sisters) of children with CCN were recruited. The siblings ranged in age between 7 and 25 years, with a mean age of 14 years. All siblings took part in opened-ended interviews and completed ecomaps to describe how they participate. Five siblings also took part in the photovoice method. Analysis involved several iterative steps, congruent with ethnography. RESULTS: Four main themes emerged as follows: (1) participation is about being part of a group; (2) it feels good; (3) I love my sibling but…; and (4) promoting participation. Siblings of children with CCN identified challenges to participation and also described ways that they participate that relate to the care of their sibling. CONCLUSIONS: Siblings prioritized the relationship with their sisters and brothers with CCN in their life, and a great deal of their participation was chosen with their sibling in mind. Sibling-to-sibling relationships were distinct and meaningful and, as a result, participation was always done mindfully and with the family needs at the forefront. Nonetheless, clinicians caring for children with CCN must keep in mind the challenges that siblings of children with CCN experience and provide strategies to siblings that will help to promote their participation in everyday life.

Comparison of the efficacy of macrocyclic lactone anthelmintics, either singly or in combination with other anthelmintic(s), in nine beef herds in southern NSW.

Anthelmintic resistance (AR) is a well-recognized challenge in farmed ruminants. The use of anthelmintics in combination is one of the strategies recommended to slow the rate of AR development. Two studies were undertaken in 2017 and 2019 to assess the efficacy of single-dose macrocyclic lactone (ML) anthelmintic and ML combination drenches. In total, 11 Faecal Egg Count Reduction Trials (FECRTs) were set up in 10 different beef herds, with results available from 10 of those FECRTs (9 herds). AR to a single ML anthelmintic was detected in all 9 herds, with resistance to Cooperia and Haemonchus spp on 9 farms, and resistance to Ostertagia and Trichostrongylus spp on 2 farms. In contrast, for the ML combination anthelmintics, all FECRTs resulted in efficacies of 99%-100%. The results suggest that cattle producers should strongly consider using combination drenches in their herds in preference to single actives.

Self-perceived participation among adults with spinal cord injury: a grounded theory study.

STUDY DESIGN: A grounded theory study of 19 adults with spinal cord injury was conducted. Participants engaged in individual in-depth interviews, and took photographs of aspects of their environment that promoted and restricted participation. Analysis consisted of an inductive process of constant comparison. A focus group with participants was held to discuss and contribute to the credibility of findings. OBJECTIVES: To develop a theoretical understanding of the influences on self-perceived participation for individuals with SCI. SETTING: Manitoba, Canada. RESULTS: The constructed grounded theory model is summarized as follows: negotiating the body-environment interface is a continuous process for those living with a SCI. Despite the relative stability of their changed body, they live in a changed world, one that is perceived differently after SCI. People use various strategies to interact within their environment, to engage in a process of participation. Intervening conditions are the environmental aspects that serve as barriers or facilitators to this process of participation. CONCLUSIONS: Study findings lend support to the need for a self-perceived definition of participation. The theory constructed in this study can be used to target interventions intended to improve the participation experiences of individuals with SCI.

Arrested DNA replication in Xenopus and release by Escherichia coli mutagenesis proteins.

Xenopus oocytes and oocyte nuclear extracts repair ultraviolet photoproducts on double-stranded (ds) DNA and replicate single-stranded (ss) to ds DNA. M13 ss DNA molecules containing cyclobutane pyrimidine dimers were maintained but not replicated in Xenopus oocytes yet were replicated in progesterone-matured oocytes. The replication arrest functioned only in cis. The replication arrest was alleviated by injection into oocytes of messenger RNAs encoding the prokaryotic mutagenesis proteins UmuD'C or MucA'B. These results may help explain how cells stabilize repair or replication events on DNA with unrepairable lesions.

5'-Deoxyribose phosphate lyase activity of human DNA polymerase iota in vitro.

DNA polymerase iota (pol iota) is one of several recently discovered DNA polymerases in mammalian cells whose function is unknown. We report here that human pol iota has an intrinsic 5'-deoxyribose phosphate (dRP) lyase activity. In reactions reconstituted with uracil-DNA glycosylase (UDG), apurinic/apyrimidinic (AP) endonuclease and DNA ligase I, pol iota can use its dRP lyase and polymerase activities to repair G*U and A*U pairs in DNA. These data and three distinct catalytic properties of pol iota implicate it in specialized forms of base excision repair (BER).

Geometric means provide a biased efficacy result when conducting a faecal egg count reduction test (FECRT).

The process of conducting a faecal egg count reduction test was simulated to examine whether arithmetic or geometric means offer the best estimate of efficacy in a situation where the true efficacy is known. Two components of sample variation were simulated: selecting hosts from the general population which was modelled by the negative binomial distribution (NBD), and taking an aliquot of faeces from the selected host to estimate the worm egg count by assuming a Poisson distribution of sample counts. Geometric mean counts were determined by adding a constant (C) to each count prior to log transformation, C was set at 25, 12 or 1. Ten thousand Monte Carlo simulations were run to estimate mean efficacy, the 2.5% (lower) and the 97.5% (upper) percentile based on arithmetic or geometric means. Arithmetic means best estimated efficacy for all different levels of worm aggregation. For moderate levels of aggregation and with C=1 the geometric mean substantially overestimated efficacy. The bias was reduced if C was increased to 25 but the results were no better than those based on arithmetic means. For very high levels of aggregation (over-dispersed populations) the geometric mean underestimated efficacy regardless of the size of C. It is recommended that the guidelines on anthelmintic resistance be revised to advocate the use of arithmetic means to estimate efficacy.

The application of faecal egg count results and statistical inference for clinical decision making in foals.

This study investigated the impact of variability in Parascaris spp. and strongyle faecal egg counts (FEC) from foals on treatment decision-making and detection of a patent infection. A single faecal sample was collected once daily for three days from 53 foals and a FEC was performed on three separate portions of each sample (total of nine egg counts per foal). Differences in the decision to administer an anthelmintic using the results of a single count (C1), the mean of three (X¯1-3) or nine counts (X¯1-9) and the upper 5% confidence limit of the gamma confidence interval (CI) of the estimate of the distribution mean (µ) from three (UCL1-3) and nine counts (UCL1-9) were determined for a range of egg count thresholds. The UCL1-9 was used as the best estimate of µ, hypothesis testing for treatment and the comparison of treatment decision-making using C1, X¯1-3, X¯1-9 and UCL1-3. The results of this study demonstrated that a point estimate (C1 or X¯1-3) was of limited value for estimating the distribution mean of egg counts in faeces and there was overall poor agreement in treatment decision-making for individual foals using C1 compared with UCL1-9. Of the foals with C1 of zero eggs per gram, 54% and 47% had Parascaris and strongyle eggs in subsequent counts, respectively. The egg density in faeces is inhomogeneous, resulting in considerable variability in egg count results for an individual foal: between faecal piles, different portions of a faecal pile and days. The use of the negative binomial distribution CI for µ takes this variability into account and is recommended for use when interpreting FEC data from horses.

A producer survey of knowledge and practises on gastrointestinal nematode control within the Australian goat industry.

Gastrointestinal nematodes (GINs) have been identified in Australia as a major problem in goat production, with few anthelmintics registered for use in goats. Therefore, anecdotally many producers use anthelmintics that have not been registered for goats. Using unregistered products could increase selection pressure for anthelmintic resistance as well as safety and/or meat or milk chemical residues of products from treated goats. This producer survey was conducted in 2014 to establish Australian goat producer knowledge, perception and practises of GIN treatment and control. Eighty-eight producers responded to the survey. Of these respondents, 90% thought that GINs were a problem for the Australian goat industry, and 73% considered GINs had caused production losses or health impacts for their goats during the 5 years prior to the survey. With regard to anthelmintic resistance, 7% believed that anthelmintic resistance was not a problem at all, 93% acknowledged anthelmintic resistance was a problem in Australian goats herds, with 25% of these reporting their properties as being affected. The majority (81%) of respondents believed the number of anthelmintics registered for goats was inadequate for effective GIN control. Of the 85% of producers who used an anthelmintic during the survey period, 69% had used a treatment not registered for use in goats. Fifty respondents listed the anthelmintic dosage used, and 50% of those had used a dose rate greater than the recommended label dose. The average frequency of administration of anthelmintic was 2.5 times per annum. Of the 51% of respondents who listed the frequency of their treatments given during the survey period, 16% administered four or more treatments annually to the majority of their goats and 8% administered treatments on an "as needed" basis. Faecal egg count (FEC) had been performed on 72% of properties in at least one of the six years covered by the survey. These results indicated that the majority of surveyed producers use anthelmintics that are not registered for use in goats and at different dose rates to label. These practises have the potential for increasing the spread of anthelmintic resistance in the GIN populations of goats and sheep. Further, giving dose rates in excess of label recommendations could impact goat safety and/or product residues. Further research is needed to investigate these risks and evaluate more sustainable GIN control options for goat herds. In addition more effective dissemination of information is necessary for the improvement of the Australian goat industry.

Effects of the absence of protozoa from birth or from weaning on the growth and methane production of lambs.

Merino ewes (n 108) joined to a single sire were allocated into three flocks, with ewes in one flock being chemically defaunated in the second month of gestation. Single lambs born to defaunated ewes (BF lambs) were heavier at birth and at weaning than lambs born to faunated ewes (F lambs). After weaning, all BF and F lambs were individually housed then half of the F lambs were chemically defaunated (DF lambs). In trial 1, BF, DF and F lambs were offered a concentrate-based diet containing either 14 or 19 % protein for a 10-week period. Wool growth rate of BF lambs was 10 % higher than that of DF or F lambs and was increased 9 % by the high-protein diet. While there was no main effect of protozoa treatment on enteric methane production, there was an interaction between protozoa treatment and diet for methane production. BF and DF lambs produced more methane than F lambs when fed the low-protein diet but when fed the high-protein diet, emissions were less than (BF lambs) or not different from (DF lambs) emissions from F lambs. In trial 2, lambs were offered 800 g roughage per d and, again, methane production was not affected by the presence of protozoa in the rumen. The data indicate that while lambs without rumen protozoa have greater protein availability than do faunated ruminants, there is no main effect of rumen protozoa on enteric methane production by lambs fed either a concentrate or roughage diet.

Insights into the knowledge, practices and training needs of veterinarians working with smallholder livestock producers in Australia.

The location of properties holding livestock is fluid; edging towards the boundaries of urban Australia, increasing the likelihood that veterinarians will be exposed to livestock as part of the provision of routine veterinary services. This study was conducted to ascertain the challenges, knowledge level and training needs of veterinarians working within this landscape, with the ultimate aim of informing the development of resources and training to better equip them in this capacity. For this purpose, a cross-sectional study, using a self-administered questionnaire was conducted among Australian veterinarians. The questionnaire comprised a mixture of 47 short closed, semi-closed and open-ended questions and was available for electronic distribution. Data was analysed descriptively and logistic regression analysis was used to identify potential factors associated with knowledge and practices of veterinarians in relation to smallholders. Complete responses were obtained from 91 veterinarians. The main livestock species kept by smallholder clients were sheep, goats, and cattle; with on-farm visits reported the most frequent interaction type, and responding to emergency situations the most frequently performed activity. The challenges experienced by veterinarians when working with smallholders were mostly related to external factors such as; lack of facilities, lack of client knowledge on animal health management and client's financial constraints. Over 95% of respondents provided some level of biosecurity advice and zoonotic disease information as part of their routine veterinary service. Although veterinarians provide advice and support to smallholders, only 14.5% considered themselves to be highly influential on smallholder practices. Confidence level in investigating disease differed by livestock species, with lower confidence reported in pigs, poultry and alpaca. Respondents were open to receiving assistance to support smallholders on matters related to disease, welfare or biosecurity, with other veterinarians (government and private), reported as the most frequently utilised resource. Having access to materials that could be distributed to smallholders was considered to be an effective way in which to provide information. While the risk of zoonotic disease was considered a challenge associated with working with smallholders, respondent's use of personal protective equipment (PPE), whilst performing common veterinary activities, was in many instances inadequate. Similarly, vaccination levels among veterinarians and other workers within the veterinary practice to prevent zoonotic diseases were variable. This study provides an insight into the way in which veterinarians engage with smallholders and highlight the importance of providing both groups with the tools necessary to manage the livestock to which are exposed.

Understanding animal health communication networks among smallholder livestock producers in Australia using stakeholder analysis.

Smallholder livestock producers are a diverse population with wide ranging motivations for keeping livestock. The biosecurity risk posed by smallholders has been the subject of much conjecture, with comparisons often made between the level of animal health and biosecurity knowledge of smallholders, versus that of commercial livestock producers. This research aimed to gain a better understanding of current knowledge of smallholder production in Australia, particularly in relation to biosecurity and emergency animal disease, and to investigate the relationships that exist between smallholders and the organisations and individuals from which they seek information, assistance and support. Engagement with stakeholders is an important component of an effective biosecurity communication strategy as the dissemination of biosecurity related information from a single source cannot be expected to satisfy the needs of such a broad ranging population. A qualitative study involving a review of literature, semi-structured interviews with government and non-government stakeholders and the development of smallholder and stakeholder influence and interest grids was undertaken. This paper forms part of a broader mixed methods research project among smallholders. Results from the stakeholder analysis showed variation in the parameters used to define smallholders and in the level of stakeholder involvement. Smallholders identified breeding consultants, other producers, private veterinarians and family, friends and colleagues as having a significant to high level of interest and potential to influence their practices. Government agencies were perceived to only have some level of interest but significant influence. Industry stakeholders and rural suppliers were positioned in the quadrant reflecting perceived low levels of interest and influence. The interest and influence grid developed from stakeholder's perspectives demonstrate a clustering around the mid points for both interest and influence, with the exception of those from industry who described low levels of interest and influence. Commonwealth and State government stakeholders reported a higher level of interest than influence. Veterinarians, both government and private, reported some to significant levels of interest and influence. In contrast to the results from the smallholder grid, rural suppliers reported relatively high levels of both interest and influence. The current study demonstrates that to maximise the effectiveness of biosecurity communication, there is a need for government and industry organisations to further engage with all stakeholders involved with smallholders.

Sulfolobus solfataricus P2 DNA polymerase IV (Dpo4): an archaeal DinB-like DNA polymerase with lesion-bypass properties akin to eukaryotic poleta.

Phylogenetic analysis of Y-family DNA polymerases suggests that it can be subdivided into several discrete branches consisting of UmuC/DinB/Rev1/Rad30/Rad30A and Rad30B. The most diverse is the DinB family that is found in all three kingdoms of life. Searches of the complete genome of the crenarchaeon Sulfolobus solfataricus P2 reveal that it possesses a DinB homolog that has been termed DNA polymerase IV (Dpo4). We have overproduced and purified native Dpo4 protein and report here its enzymatic characterization. Dpo4 is thermostable, but can also synthesize DNA at 37 degrees C. Under these conditions, the enzyme exhibits misinsertion fidelities in the range of 8 x 10(-3) to 3 x 10(-4). Dpo4 is distributive but at high enzyme to template ratios can synthesize long stretches of DNA and can substitute for Taq polymerase in PCR. On damaged DNA templates, Dpo4 can facilitate translesion replication of an abasic site, a cis-syn thymine-thymine dimer, as well as acetyl aminofluorene adducted- and cisplatinated-guanine residues. Thus, although phylogenetically related to DinB polymerases, our studies suggest that the archaeal Dpo4 enzyme exhibits lesion-bypass properties that are, in fact, more akin to those of eukaryotic poleta.

The UmuD' protein filament and its potential role in damage induced mutagenesis.

BACKGROUND: Damage induced 'SOS mutagenesis' may occur transiently as part of the global SOS response to DNA damage in bacteria. A key participant in this process is the UmuD protein, which is produced in an inactive from but converted to the active form, UmuD', by a RecA-mediated self-cleavage reaction. UmuD', together with UmuC and activated RecA (RecA*), enables the DNA polymerase III holoenzyme to replicate across chemical and UV induced lesions. The efficiency of this reaction depends on several intricate protein-protein interactions. RESULTS: Recent X-ray crystallographic analysis shows that in addition to forming molecular dimers, the N- and C-terminal tails of UmuD' extend from a globular beta structure to associate and produce crystallized filaments. We have investigated this phenomenon and find that these filaments appear to relate to biological activity. Higher order oligomers are found in solution with UmuD', but not with UmuD nor with a mutant of UmuD' lacking the extended N terminus. Deletion of the N terminus of UmuD' does not affect its ability to form molecular dimers but does severely compromise its ability to interact with a RecA-DNA filament and to participate in mutagenesis. Mutations in the C terminus of UmuD' result in both gain and loss of function for mutagenesis. CONCLUSIONS: The activation of UmuD to UmuD' appears to cause a large conformational change in the protein which allows it to form oligomers in solution at physiologically relevant concentrations. Properties of these oligomers are consistent with the filament structures seen in crystals of UmuD'.

Inhomogeneity of the density of Parascaris spp. eggs in faeces of individual foals and the use of hypothesis testing for treatment decision making.

Faecal egg counts (FEC) are used widely for monitoring of parasite infection in animals, treatment decision-making and estimation of anthelmintic efficacy. When a single count or sample mean is used as a point estimate of the expectation of the egg distribution over some time interval, the variability in the egg density is not accounted for. Although variability, including quantifying sources, of egg count data has been described, the spatiotemporal distribution of nematode eggs in faeces is not well understood. We believe that statistical inference about the mean egg count for treatment decision-making has not been used previously. The aim of this study was to examine the density of Parascaris eggs in solution and faeces and to describe the use of hypothesis testing for decision-making. Faeces from two foals with Parascaris burdens were mixed with magnesium sulphate solution and 30 McMaster chambers were examined to determine the egg distribution in a well-mixed solution. To examine the distribution of eggs in faeces from an individual animal, three faecal piles from a foal with a known Parascaris burden were obtained, from which 81 counts were performed. A single faecal sample was also collected daily from 20 foals on three consecutive days and a FEC was performed on three separate portions of each sample. As appropriate, Poisson or negative binomial confidence intervals for the distribution mean were calculated. Parascaris eggs in a well-mixed solution conformed to a homogeneous Poisson process, while the egg density in faeces was not homogeneous, but aggregated. This study provides an extension from homogeneous to inhomogeneous Poisson processes, leading to an understanding of why Poisson and negative binomial distributions correspondingly provide a good fit for egg count data. The application of one-sided hypothesis tests for decision-making is presented.

Regulation of UmuD cleavage: role of the amino-terminal tail.

An essential step in SOS mutagenesis is the RecA-mediated posttranslational processing of UmuD-like proteins to the shorter, but mutagenically active, UmuD'-like proteins. Interestingly, the UmuD-like proteins undergo posttranslational processing at different rates. For example, although the Escherichia coli UmuD (UmuDEc) and the Salmonella typhimurium UmuD (UmuDSt) proteins are 73% identical, UmuDSt is processed in vivo at a significantly faster rate than the UmuDEc protein. Here, we report experiments aimed at investigating the molecular basis of these phenotypic differences. The faster rate of UmuDSt cleavage probably does not result solely from a better interaction with RecA, since we observed that, in vitro, UmuDSt undergoes RecA-independent autocatalytic processing about four-times faster than UmuDEc. By constructing chimeric UmuD proteins, we determined that the amino-terminal tail of the UmuD proteins proximal to the Cys24-Gly25 cleavage site is mainly responsible for the difference in UmuDSt and UmuDEc cleavage rates. Site-directed mutagenesis of the UmuDEc protein suggests that most of the enhanced cleavage observed with the UmuDSt protein can be attributed to the presence of a Pro23 residue, juxtaposed to the cleavage site in UmuDSt. Furthermore, this proline residue appears to result in a UmuD protein that is a much better substrate for intermolecular cleavage. These findings clearly implicate the N-terminal tail of the UmuD-like proteins as playing an important and unexpected regulatory function in the maturation of the mutagenically active UmuD'-like mutagenesis proteins.

Intermolecular cleavage by UmuD-like enzymes: identification of residues required for cleavage and substrate specificity.

The UmuD-like proteins are best characterized for their role in damage-induced SOS mutagenesis. An essential step in this process is the enzymatic self-processing of the UmuD-like proteins. This reaction is thought to occur either via an intramolecular or intermolecular self-cleavage mechanism. Here, we demonstrate that it can also occur via an heterologous intermolecular cleavage reaction. The Escherichia coli UmuD enzyme demonstrated the broadest substrate specificity, cleaving both E. coli and Salmonella typhimurium UmuD substrates in vivo. In comparison, the wild-type S. typhimurium UmuD (UmuDSt) and MucA enzymes catalyzed intermolecular self-cleavage, but did not facilitate heterologous cleavage. Heterologous cleavage by the UmuDSt enzyme was, however, observed with chimeric UmuD substrates that possess residues 30-55 of UmuDSt. We have further localized the residue predominantly responsible for UmuDSt-catalyzed heterologous cleavage to Ser50 in the substrate molecule. We hypothesize that changes at this residue affect the positioning of the cleavage site of a substrate molecule within the catalytic cleft of the UmuDSt enzyme by affecting the formation of a so-called UmuD "filament-dimer". This hypothesis is further supported by the observation that mutations known to disrupt an E. coli UmuD' filament dimer also block intermolecular UmuDEc cleavage.

Visualization of two binding sites for the Escherichia coli UmuD'(2)C complex (DNA pol V) on RecA-ssDNA filaments.

The heterotrimeric UmuD'(2)C complex of Escherichia coli has recently been shown to possess intrinsic DNA polymerase activity (DNA pol V) that facilitates error-prone translesion DNA synthesis (SOS mutagenesis). When overexpressed in vivo, UmuD'(2)C also inhibits homologous recombination. In both activities, UmuD'(2)C interacts with RecA nucleoprotein filaments. To examine the biochemical and structural basis of these reactions, we have analyzed the ability of the UmuD'(2)C complex to bind to RecA-ssDNA filaments in vitro. As estimated by a gel retardation assay, binding saturates at a stoichiometry of approximately one complex per two RecA monomers. Visualized by cryo-electron microscopy under these conditions, UmuD'(2)C is seen to bind uniformly along the filaments, such that the complexes are completely submerged in the deep helical groove. This mode of binding would impede access to DNA in a RecA filament, thus explaining the ability of UmuD'(2)C to inhibit homologous recombination. At sub-saturating binding, the distribution of UmuD'(2)C complexes along RecA-ssDNA filaments was characterized by immuno-gold labelling with anti-UmuC antibodies. These data revealed preferential binding at filament ends (most likely, at one end). End-specific binding is consistent with genetic models whereby such binding positions the UmuD'(2)C complex (pol V) appropriately for its role in SOS mutagenesis.

The Saccharomyces cerevisiae RAD30 gene, a homologue of Escherichia coli dinB and umuC, is DNA damage inducible and functions in a novel error-free postreplication repair mechanism.

Damage-inducible mutagenesis in prokaryotes is largely dependent upon the activity of the UmuD'C-like proteins. Since many DNA repair processes are structurally and/or functionally conserved between prokaryotes and eukaryotes, we investigated the role of RAD30, a previously uncharacterized Saccharomyces cerevisiae DNA repair gene related to the Escherichia coli dinB, umuC and S. cerevisiae REV1 genes, in UV resistance and UV-induced mutagenesis. Similar to its prokaryotic homologues, RAD30 was found to be damage inducible. Like many S. cerevisiae genes involved in error-prone DNA repair, epistasis analysis clearly places RAD30 in the RAD6 group and rad30 mutants display moderate UV sensitivity reminiscent of rev mutants. However, unlike rev mutants, no defect in UV-induced reversion was seen in rad30 strains. While rad6 and rad18 are both epistatic to rad30, no epistasis was observed with rev1, rev3, rev7 or rad5, all of which are members of the RAD6 epistasis group. These findings suggest that RD30 participates in a novel error-free repair pathway dependent on RAD6 and RAD18, but independent of REV1, REV3, REV7 and RAD5.

Selective inhibition of RecA functions by the Hc1 nucleoid condensation protein from Chlamydia trachomatis.

During the normal biphasic life cycle of Chlamydia trachomatis, the histone-like protein Hc1 promotes the condensation of nucleoids in elementary bodies, it may also displace nucleoproteins, including repair functions from chromatin. Hc1 was found to effectively inhibit the recombination and repair of the weak binding RecA430 mutant protein from Escherichia coli, but had minimal effects on the parental RecA(+) protein. Expression of Hc1 was also found to inhibit the repair activities of the C. trachomatis RecA protein but not recombination. These results suggest that chlamydial RecA may have evolved mechanisms to minimize Hc1 competition for recombinational activities.