Supertertiary protein structure affects an allosteric network.

The notion that protein function is allosterically regulated by structural or dynamic changes in proteins has been extensively investigated in several protein domains in isolation. In particular, PDZ domains have represented a paradigm for these studies, despite providing conflicting results. Furthermore, it is still unknown how the association between protein domains in supramodules, consitituting so-called supertertiary structures, affects allosteric networks. Here, we experimentally mapped the allosteric network in a PDZ:ligand complex, both in isolation and in the context of a supramodular structure, and show that allosteric networks in a PDZ domain are highly dependent on the supertertiary structure in which they are present. This striking sensitivity of allosteric networks to the presence of adjacent protein domains is likely a common property of supertertiary structures in proteins. Our findings have general implications for prediction of allosteric networks from primary and tertiary structures and for quantitative descriptions of allostery.

Co-Occurrence of Prevalent Symptoms in Patients Receiving Hemodialysis - A Cross-Sectional Survey.

Patients with chronic kidney disease undergoing hemodialysis generally have a significant symptom burden, which may interfere with their quality of life. The aim of this study was to identify the prevalence of fatigue, pain, anxiety, and depression in patients on hemodialysis and analyze their co-occurrence. A cross-sectional study used self-reported measures. A total of 242 patients aged 18 years or older were initially screened; 141 were included in the study; 129 answered the questionnaires (response rate 91%). Preva lences were 24.8% had moderate to severe fatigue, 38.0% had pain, 32.6% had anxiety, and 29.5% had depression. The prevalence of coexistent moderate to severe symptoms ranged from 15.5% to 25.6%. Further research is needed to better understand the symptom burden and their co-occurrence in patients receiving hemodialysis.

Divergent Evolution of a Protein-Protein Interaction Revealed through Ancestral Sequence Reconstruction and Resurrection.

The postsynaptic density extends across the postsynaptic dendritic spine with discs large (DLG) as the most abundant scaffolding protein. DLG dynamically alters the structure of the postsynaptic density, thus controlling the function and distribution of specific receptors at the synapse. DLG contains three PDZ domains and one important interaction governing postsynaptic architecture is that between the PDZ3 domain from DLG and a protein called cysteine-rich interactor of PDZ3 (CRIPT). However, little is known regarding functional evolution of the PDZ3:CRIPT interaction. Here, we subjected PDZ3 and CRIPT to ancestral sequence reconstruction, resurrection, and biophysical experiments. We show that the PDZ3:CRIPT interaction is an ancient interaction, which was likely present in the last common ancestor of Eukaryotes, and that high affinity is maintained in most extant animal phyla. However, affinity is low in nematodes and insects, raising questions about the physiological function of the interaction in species from these animal groups. Our findings demonstrate how an apparently established protein-protein interaction involved in cellular scaffolding in bilaterians can suddenly be subject to dynamic evolution including possible loss of function.

Process, content, and experiences of delivering the Carer Support Needs Assessment Tool Intervention (CSNAT-I) in the Danish specialised palliative care setting.

PURPOSE: The Carer Support Needs Assessment Tool Intervention (CSNAT-I) has shown positive effects in the Danish specialised palliative care (SPC) setting. Here, we explore the process, content, and experiences of delivering the CSNAT-I. METHODS: Data were collected during a stepped wedge cluster randomised controlled trial investigating the impact of the CSNAT-I in the Danish SPC setting in 2018-2019. Data were obtained from the CSNAT (tool) completed by caregivers, from health care professionals' (HCPs') written documentation of the CSNAT-I, and from semi-structured interviews with HCPs. RESULTS: The study population consisted of the 130 caregivers receiving a first CSNAT-I within 13 days of study enrolment, the 93 caregivers receiving a second CSNAT-I 15-27 days after enrolment, and the 44 HCPs delivering the intervention. Top three domains of unmet caregiver support needs reported in the CSNAT-I were: "knowing what to expect in the future," "dealing with feelings and worries," and "understanding the illness." These domains together with "knowing who to contact if concerned" and "talking to the patient about the illness" were also the domains most frequently prioritised for discussion with HCPs. According to HCPs, most often support delivered directly by HCPs themselves during the actual contact (e.g., listening, advice, information) was sufficient. Overall, HCPs experienced the CSNAT-I as constructive and meaningful, and difficulties in delivering the intervention were rarely an issue. CONCLUSION: The support needs reported by caregivers confirm the relevance of the CSNAT-I. HCPs' overall experiences of the clinical feasibility and relevance of the CSNAT-I were very positive. ClinicalTrials.gov ID: NCT03466580. Date of registration: March 1, 2018.

Identification of palliative care needs in hemodialysis patients: An update.

OBJECTIVE: End-stage kidney disease and hemodialysis (HD) treatment are associated with a high symptom burden in many patients. This study aimed at updating patient-reported outcomes concerning quality of life, fatigue, anxiety, and depression in HD patients treated in a single center in order to assess the need for palliative care provision. METHOD: A cross-sectional design, in which a sample of patients treated at a single HD department (Rigshospitalet, Denmark) between January and June 2019, was analyzed using the Kidney Disease Quality of Life Short Form, the Multidimensional Fatigue Inventory, and the Hospital Anxiety and Depression Scale. In addition, we compared the results with previously published data from the same department (2000) and with an age- and sex-matched sample from the Danish general population (1997/2014). Chi-square and t-tests were used for comparisons. RESULTS: Screened patients = 242, included = 141, analyzed = 131 (70.2% male, mean age = 61.3 years). HD patients reported low scores for quality of life, high scores for fatigue, and approximately 30% had anxiety/depression. Regarding quality of life, they had significantly lower scores on general health (P ≤ 0.000), vitality (P = 0.009), social functioning (P = 0.001), mental health (P = 0.007), and mental component (P = 0.005) compared with former data of HD patients. Moreover, they reported significantly poorer quality of life and worse fatigue compared with the general Danish population. SIGNIFICANCE OF RESULTS: In the patients undergoing HD, quality of life was poor and worsened when compared with former HD patients' data. Additionally, fatigue, depression, and anxiety in HD patients were prevalent. A clear need for palliative care provision was observed.

Functional interplay between protein domains in a supramodular structure involving the postsynaptic density protein PSD-95.

Cell scaffolding and signaling are governed by protein-protein interactions. Although a particular interaction is often defined by two specific domains binding to each other, this interaction often occurs in the context of other domains in multidomain proteins. How such adjacent domains form supertertiary structures and modulate protein-protein interactions has only recently been addressed and is incompletely understood. The postsynaptic density protein PSD-95 contains a three-domain supramodule, denoted PSG, which consists of PDZ, Src homology 3 (SH3), and guanylate kinase-like domains. The PDZ domain binds to the C terminus of its proposed natural ligand, CXXC repeat-containing interactor of PDZ3 domain (CRIPT), and results from previous experiments using only the isolated PDZ domain are consistent with the simplest scenario for a protein-protein interaction; namely, a two-state mechanism. Here we analyzed the binding kinetics of the PSG supramodule with CRIPT. We show that PSG binds CRIPT via a more complex mechanism involving two conformational states interconverting on the second timescale. Both conformational states bound a CRIPT peptide with similar affinities but with different rates, and the distribution of the two conformational states was slightly shifted upon CRIPT binding. Our results are consistent with recent structural findings of conformational changes in PSD-95 and demonstrate how conformational transitions in supertertiary structures can shape the ligand-binding energy landscape and modulate protein-protein interactions.

Cholesterol binding to a conserved site modulates the conformation, pharmacology, and transport kinetics of the human serotonin transporter.

The serotonin transporter (SERT) is important for reuptake of the neurotransmitter serotonin from the synaptic cleft and is also the target of most antidepressants. It has previously been shown that cholesterol in the membrane bilayer affects the conformation of SERT. Although recent crystal structures have identified several potential cholesterol-binding sites, it is unclear whether any of these potential cholesterol sites are occupied by cholesterol and functionally relevant. In the present study, we focus on the conserved cholesterol site 1 (CHOL1) located in a hydrophobic groove between TM1a, TM5, and TM7. By molecular dynamics simulations, we demonstrate a strong binding of cholesterol to CHOL1 in a membrane bilayer environment. In biochemical experiments, we find that cholesterol depletion induces a more inward-facing conformation favoring substrate analog binding. Consistent with this, we find that mutations in CHOL1 with a negative impact on cholesterol binding induce a more inward-facing conformation, and, vice versa, mutations with a positive impact on cholesterol binding induce a more outward-facing conformation. This shift in transporter conformation dictated by the ability to bind cholesterol in CHOL1 affects the apparent substrate affinity, maximum transport velocity, and turnover rates. Taken together, we show that occupation of CHOL1 by cholesterol is of major importance in the transporter conformational equilibrium, which in turn dictates ligand potency and serotonin transport activity. Based on our findings, we propose a mechanistic model that incorporates the role of cholesterol binding to CHOL1 in the function of SERT.

Table in the corner: a qualitative study of life situation and perspectives of the everyday lives of oesophageal cancer patients in palliative care.

BACKGROUND: Incurable oesophageal cancer patients are often affected by existential distress and deterioration of quality of life. Knowledge about the life situation of this patient group is important to provide relevant palliative care and support. The purpose of this study is to illuminate the ways in which incurable oesophageal cancer disrupts the patients' lives and how the patients experience and adapt to life with the disease. METHODS: Seventeen patients receiving palliative care for oesophageal cancer were interviewed 1-23 months after diagnosis. The epistemological approach was inspired by phenomenology and hermeneutics, and the method of data collection, analysis and interpretation consisted of individual qualitative interviews and meaning condensation, inspired by Kvale and Brinkmann. RESULTS: The study reveals how patients with incurable oesophageal cancer experience metaphorically to end up at a "table in the corner". The patients experience loss of dignity, identity and community. The study illuminated how illness and symptoms impact and control daily life and social relations, described under these subheadings: "sense of isolation"; "being in a zombie-like state"; "one day at a time"; and "at sea". Patients feel alone with the threat to their lives and everyday existence; they feel isolated due to the inhibiting symptoms of their illness, anxiety, worry and daily losses and challenges. CONCLUSIONS: The patients' lives are turned upside down, and they experience loss of health, function and familiar, daily habits. The prominent issues for the patients are loneliness and lack of continuity. As far as their normal everyday lives, social networks and the health system are concerned, patients feel they have been banished to a "table in the corner". These patients have a particular need for healthcare professionals who are dedicated to identifying what can be done to support the patients in their everyday lives, preserve dignity and provide additional palliative care.

Early Feasibility of an Activity-Based Intervention for Improving Ingestive Functions in Older Adults with Oropharyngeal Dysphagia.

There is growing awareness about the use of combined strength- and skill-based swallowing training for improving swallowing physiology in the event of dysphagia. Such an approach involves focusing on coordination and timing as well as swallowing strengthening in the context of increased exercise complexity in eating and drinking activities. This study aimed to determine the early feasibility of a newly developed 12-week intervention, named the ACT-ING program (ACTivity-based strength and skill training of swallowing to improve INGestion), in older adults with dysphagia and generalized sarcopenia. In a multiple-case-study design, seven participants above 65 years of age (five women and two men) with slight to severe dysphagia and indications of sarcopenia underwent the intervention during hospitalization and in the community after discharge. The ACT-ING program met most of the feasibility marks in terms of demand (73.3% of those invited accepted participation), safety (100%), no reports of adverse events, tolerance (85.7%), usability (100%), and acceptability (100%). Three putative mediators of change (experienced autonomy support, in-therapy engagement, and perceived improvement in swallowing capacity) appeared to have been best accomplished in participants with slight to moderate dysphagia. The ACT-ING program showed preliminary evidence of early feasibility, warranting further early-phase dose articulation and proof-of-concept trials.

Older patients' perspectives on participating in multimodal rehabilitation including anabolic steroids following hip fracture: a qualitative study embedded within a pilot RCT.

PURPOSE: To explore patient perspectives of participating in a pilot RCT evaluating feasibility and effect of anabolic steroid, physiotherapy and nutritional supplement following hip fracture. METHODS: Semi-structured telephone-based interviews of 16 women and three men (average age 73 years) were conducted at baseline and after a 12-week intervention. Qualitative content analysis was performed. RESULTS: Two main categories were identified: (1) Trust and hope for a positive change with three sub-categories; reflections on anabolic steroids, anticipation of extra attention, lack of energy. (2) Curiosity, care, and commitment with four sub-categories; a sense of anabolic steroids, feeling of exclusivity and privileges, challenges and sense of obligation, and perspectives on personal gain. CONCLUSIONS: Findings suggest high acceptability of the intervention. Participants motivated their participation on a trust that the intervention would "do more good than harm". They found the randomization and possibility of receiving anabolic steroids intriguing, and especially valued trial participation because of their experience of getting extra care and "deluxe" rehabilitation including close contact and support by health professionals. Our findings may help inform future research recruiting older patients and generally considered relevant for health professionals in rehabilitation, emphasizing the impact of professional guidance and social support to encourage self-efficacy.Implications for rehabilitationWith muscle enhancing medicine being suggested as a supplement in rehabilitation following hip fracture, exploring patients' perspectives is warranted and may help inform future trials in this area.Factors reported as important by older adults for engaging in rehabilitation trials are: simple but thorough information, friendly and trustful relation with study staff and opportunities of extra care and attention.Older patients with hip fracture highly valued professional guidance and support by health professionals during the rehabilitation intervention. High acceptability was identified for the supervised outpatient rehabilitation, where especially the individually structured progressive strength training was highlighted as the "active ingredient" accelerating recovery and potentially promoted self-efficacy.

Determinants of affinity, specificity, and phase separation in a supramodule from Post-synaptic density protein 95.

The post-synaptic density (PSD) is a phase-separated membraneless compartment of proteins including PSD-95 that undergoes morphological alteration in response to synaptic activity. Here, we investigated the interactome of a three-domain supramodule, PDZ3-SH3-GK (PSG) from PSD-95 using bioinformatics to identify potential binding partners, and biophysical methods to characterize the interaction with peptides from these proteins. PSG and the single PDZ3 domain bound similar peptides, but with different specificity. Furthermore, we found that the protein ADGRB1 formed liquid droplets with the PSG supramodule, extending the model for PSD formation. Moreover, certain mutations, introduced outside of the binding pocket in PDZ3, increased the affinity and specificity of the interaction and the size of liquid droplets. Other mutations within the ligand binding pocket lead to a new binding motif specificity. Our results show how the context in terms of supertertiary structure modulates affinity, specificity, and phase separation, and how these properties can evolve by point mutation.

A Syntenin Inhibitor Blocks Endosomal Entry of SARS-CoV-2 and a Panel of RNA Viruses.

Viruses are dependent on host factors in order to efficiently establish an infection and replicate. Targeting the interactions of such host factors provides an attractive strategy to develop novel antivirals. Syntenin is a protein known to regulate the architecture of cellular membranes by its involvement in protein trafficking and has previously been shown to be important for human papilloma virus (HPV) infection. Here, we show that a highly potent and metabolically stable peptide inhibitor that binds to the PDZ1 domain of syntenin inhibits severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection by blocking the endosomal entry of the virus. Furthermore, we found that the inhibitor also hampered chikungunya infection and strongly reduced flavivirus infection, which is completely dependent on receptor-mediated endocytosis for their entry. In conclusion, we have identified a novel broad spectrum antiviral inhibitor that efficiently targets a broad range of RNA viruses.

Dissecting Inter-domain Cooperativity in the Folding of a Multi Domain Protein.

Correct protein folding underlies all cellular functions. While there are detailed descriptions and a good understanding of protein folding pathways for single globular domains there is a paucity of quantitative data regarding folding of multidomain proteins. We have here investigated the folding of a three-domain supramodule from the protein PSD-95, consisting of one PDZ domain, one SH3 domain and one guanylate kinase-like (GK) domain. This supramodule has previously been shown to work as one functional unit with regard to ligand binding. We used equilibrium and kinetic folding experiments to demonstrate that the PDZ domain folds faster and independently from the SH3-GK tandem, which folds as one cooperative unit. However, concurrent folding of the PDZ domain slows down folding of SH3-GK by non-native interactions, resulting in an off-pathway folding intermediate. Our data contribute to an emerging description of multidomain protein folding in which individual domains cannot a priori be viewed as separate folding units.

The antidepressant drug vilazodone is an allosteric inhibitor of the serotonin transporter.

Depression is a common mental disorder. The standard medical treatment is the selective serotonin reuptake inhibitors (SSRIs). All characterized SSRIs are competitive inhibitors of the serotonin transporter (SERT). A non-competitive inhibitor may produce a more favorable therapeutic profile. Vilazodone is an antidepressant with limited information on its molecular interactions with SERT. Here we use molecular pharmacology and cryo-EM structural elucidation to characterize vilazodone binding to SERT. We find that it exhibits non-competitive inhibition of serotonin uptake and impedes dissociation of [3H]imipramine at low nanomolar concentrations. Our SERT structure with bound imipramine and vilazodone reveals a unique binding pocket for vilazodone, expanding the boundaries of the extracellular vestibule. Characterization of the binding site is substantiated with molecular dynamics simulations and systematic mutagenesis of interacting residues resulting in decreased vilazodone binding to the allosteric site. Our findings underline the versatility of SERT allosteric ligands and describe the unique binding characteristics of vilazodone.

Optimization of Nutrition And Medication (OptiNAM) for acutely admitted older patients: protocol for a randomized single-blinded controlled trial.

BACKGROUND: Internationally, older patients (≥65 years) account for more than 40% of acute admissions. Older patients admitted to the emergency department (ED) are frequently malnourished and exposed to inappropriate medication prescribing, due in part to the inaccuracy of creatinine-based equations for estimated glomerular filtration rate (eGFR). The overall aims of this trial are to investigate: (1) the efficacy of a medication review (MED intervention) independent of nutritional status, (2) the accuracy of eGFR equations based on various biomarkers compared to measured GFR (mGFR) based on 99mTechnetium-diethylenetriaminepentaacetic acid plasma clearance, and (3) the efficacy of an individualized multimodal and transitional nutritional intervention (MULTI-NUT-MED intervention) in older patients with or at risk of malnutrition in the ED. METHODS: The trial is a single-center block randomized, controlled, observer-blinded, superiority and explorative trial with two parallel groups. The population consists of 200 older patients admitted to the ED: 70 patients without malnutrition or risk of malnutrition and 130 patients with or at risk of malnutrition defined as a Mini Nutritional Assessment-Short Form score ≤11. All patients without the risk of malnutrition receive the MED intervention, which consists of a medication review by a pharmacist and geriatrician in the ED. Patients with or at risk of malnutrition receive the MULTI-NUT-MED intervention, which consists of the MED intervention in addition to, dietary counseling and individualized interventions based on the results of screening tests for dysphagia, problems with activities of daily living, low muscle strength in the lower extremities, depression, and problems with oral health. Baseline data are collected upon study inclusion, and follow-up data are collected at 8 and 16 weeks after discharge. The primary outcomes are (1) change in medication appropriateness index (MAI) score from baseline to 8 weeks after discharge, (2) accuracy of different eGFR equations compared to mGFR, and (3) change in health-related quality of life (measured with EuroQol-5D-5L) from baseline to 16 weeks after discharge. DISCUSSION: The trial will provide new information on strategies to optimize the treatment of malnutrition and inappropriate medication prescribing among older patients admitted to the ED. TRAIL REGISTRATION: ClinicalTrials.gov NTC03741283 . Retrospectively registered on 14 November 2018.

Effect of the Carer Support Needs Assessment Tool intervention (CSNAT-I) in the Danish specialised palliative care setting: a stepped-wedge cluster randomised controlled trial.

BACKGROUND: The Carer Support Needs Assessment Tool intervention (CSNAT-I) has been shown to improve end-of-life care support for informal caregivers. This study investigated the impact of the CSNAT-I on caregivers of patients recently enrolled in specialised palliative care (SPC) at home in Denmark. METHODS: A stepped-wedge cluster randomised controlled trial with nine clusters (ie, SPC teams). Outcome measures were collected using caregiver questionnaires at baseline (T0) and 2-week (T1) and 4-week (T2) follow-up. RESULTS: A total of 437 caregivers were enrolled (control group, n=255; intervention group, n=182). No intervention effect was found on the primary outcome, caregiver strain at T1 (p=0.1865). However, positive effects were found at T1 and T2 on attention to caregivers' well-being (p<0.0001), quality of information and communication (p<0.0001), amount of information (T1: p=0.0002; T2: p<0.0001), involvement (T1: p=0.0045; T2: p<0.0001), talking about greatest burdens (p<0.0001) and assistance in managing greatest burdens (p<0.0001). The effect sizes of these differences were medium or large and seemed to increase from T1 to T2. At T1, positive effects were found on distress (p=0.0178) and home care responsibility (p=0.0024). No effect was found on the remaining outcomes. CONCLUSION: Although no effect was found on caregiver strain, the CSNAT-I showed positive effects on caregiver distress, home care responsibility and key outcomes regarding caregivers' experience of the interaction with healthcare professionals. TRIAL REGISTRATION NUMBER: NCT03466580.

Comparison of Coding Transcriptomes in Fibroblasts Irradiated With Low and High LET Proton Beams and Cobalt-60 Photons.

PURPOSE: To identify differential cellular responses after proton and photon irradiation by comparing transcriptomes of primary fibroblasts irradiated with either radiation type. METHODS AND MATERIALS: A panel of primary dermal fibroblast cultures was irradiated with low and higher linear energy transfer (LET) proton beams. Cobalt-60 photon irradiation was used as reference. Dose was delivered in 3 fractions of 3.5 Gy (relative biological effectiveness) using a relative biological effectiveness of 1.1 for proton doses. Cells were harvested 2 hours after the final fraction was delivered, and RNA was purified. RNA sequencing was performed using Illumina NextSeq 500 with high-output kit. The edgeR package in R was used for differential gene expression analysis. RESULTS: Pairwise comparisons of the transcriptomes in the 3 treatment groups showed that there were 84 and 56 differentially expressed genes in the low LET group compared with the Cobalt-60 group and the higher LET group, respectively. The higher LET proton group and the Cobalt-60 group had the most distinct transcriptome profiles, with 725 differentially regulated genes. Differentially regulated canonical pathways and various regulatory factors involved in regulation of biological mechanisms such as inflammation, carcinogenesis, and cell cycle control were identified. CONCLUSIONS: Inflammatory regulators associated with the development of normal tissue complications and malignant transformation factors seem to be differentially regulated by higher LET proton and Cobalt-60 photon irradiation. The reported transcriptome differences could therefore influence the progression of adverse effects and the risk of developing secondary cancers.

Seeking allosteric networks in PDZ domains.

Ever since Ranganathan and coworkers subjected the covariation of amino acid residues in the postsynaptic density-95/Discs large/Zonula occludens 1 (PDZ) domain family to a statistical correlation analysis, PDZ domains have represented a paradigmatic family to explore single domain protein allostery. Nevertheless, several theoretical and experimental studies in the past two decades have contributed contradicting results with regard to structural localization of the allosteric networks, or even questioned their actual existence in PDZ domains. In this review, we first describe theoretical and experimental approaches that were used to probe the energetic network(s) in PDZ domains. We then compare the proposed networks for two well-studied PDZ domains namely the third PDZ domain from PSD-95 and the second PDZ domain from PTP-BL. Our analysis highlights the contradiction between the different methods and calls for additional work to better understand these allosteric phenomena.

Role for the fission yeast RecQ helicase in DNA repair in G2.

Members of the RecQ helicase subfamily are mutated in several human genomic instability syndromes, such as Bloom, Werner, and Rothmund-Thomson syndromes. We show that Rqh1, the single Schizosaccharomyces pombe homologue, is a 3'-to-5' helicase and exists with Top3 in a high-molecular-weight complex. top3 deletion is inviable, and this is suppressed by concomitant loss of rqh1 helicase activity or loss of recombination functions. This is consistent with RecQ helicases in other systems. By using epistasis analysis of the UV radiation sensitivity and by analyzing the kinetics of Rhp51 (Rad51 homologue), Rqh1, and Top3 focus formation in response to UV in synchronized cells, we identify the first evidence of a function for Rqh1 and Top3 in the repair of UV-induced DNA damage in G(2). Our data provide evidence that Rqh1 functions after Rad51 focus formation during DNA repair. We also identify a function for Rqh1 upstream of recombination in an Rhp18-dependent (Rad18 homologue) pathway. The model that these data allow us to propose helps to reconcile different interpretations of RecQ family helicase function that have arisen between work based on the S. pombe system and models based on studies of Saccharomyces cerevisiae SGS1 suggesting that RecQ helicases act before Rad51.

Radiogenomics - current status, challenges and future directions.

Radiogenomics designates a scientific field that addresses possible associations between genetic germline alterations and normal tissue toxicity after radiotherapy. The ultimate aim of this research is to establish a gene-based predictive test for normal tissue radiosensitivity. During the last 5 years, substantial progress has been achieved in this field. Several compelling associations for SNPs have been demonstrated in large candidate gene studies as well as genome wide association studies. These findings shed new light on radiobiology and expand our understanding of the processes that lead to side effects after radiotherapy. Despite this, certain fundamental challenges still relate to genomic approaches. Based on the latest insights into complex trait genetics and molecular genetics, we provide an analysis of these challenges and propose putative strategies to further advance the field. These strategies include 'big data approaches' and collaborative research within international consortia. Furthermore, research that combines the study of radiation-induced gene expression and genome-wide SNP genotype may discover genetic alterations that regulate the biological response to ionizing radiation. Thus, such integrative approaches may lead to genetic alterations that affect risk of normal tissue toxicity.