SMAD3 promotes expression and activity of the androgen receptor in prostate cancer.

Overexpression of androgen receptor (AR) is the primary cause of castration-resistant prostate cancer, although mechanisms upregulating AR transcription in this context are not well understood. Our RNA-seq studies revealed that SMAD3 knockdown decreased levels of AR and AR target genes, whereas SMAD4 or SMAD2 knockdown had little or no effect. ChIP-seq analysis showed that SMAD3 knockdown decreased global binding of AR to chromatin. Mechanistically, we show that SMAD3 binds to intron 3 of the AR gene to promote AR expression. Targeting these binding sites by CRISPRi reduced transcript levels of AR and AR targets. In addition, ∼50% of AR and SMAD3 ChIP-seq peaks overlapped, and SMAD3 may also cooperate with or co-activate AR for AR target expression. Functionally, AR re-expression in SMAD3-knockdown cells partially rescued AR target expression and cell growth defects. The SMAD3 peak in AR intron 3 overlapped with H3K27ac ChIP-seq and ATAC-seq peaks in datasets of prostate cancer. AR and SMAD3 mRNAs were upregulated in datasets of metastatic prostate cancer and CRPC compared with primary prostate cancer. A SMAD3 PROTAC inhibitor reduced levels of AR, AR-V7 and AR targets in prostate cancer cells. This study suggests that SMAD3 could be targeted to inhibit AR in prostate cancer.

The deubiquitinase USP36 promotes snoRNP group SUMOylation and is essential for ribosome biogenesis.

SUMOylation plays a crucial role in regulating diverse cellular processes including ribosome biogenesis. Proteomic analyses and experimental evidence showed that a number of nucleolar proteins involved in ribosome biogenesis are modified by SUMO. However, how these proteins are SUMOylated in cells is less understood. Here, we report that USP36, a nucleolar deubiquitinating enzyme (DUB), promotes nucleolar SUMOylation. Overexpression of USP36 enhances nucleolar SUMOylation, whereas its knockdown or genetic deletion reduces the levels of SUMOylation. USP36 interacts with SUMO2 and Ubc9 and directly mediates SUMOylation in cells and in vitro. We show that USP36 promotes the SUMOylation of the small nucleolar ribonucleoprotein (snoRNP) components Nop58 and Nhp2 in cells and in vitro and their binding to snoRNAs. It also promotes the SUMOylation of snoRNP components Nop56 and DKC1. Functionally, we show that knockdown of USP36 markedly impairs rRNA processing and translation. Thus, USP36 promotes snoRNP group SUMOylation and is critical for ribosome biogenesis and protein translation.

Histone demethylase JMJD1A in cancer progression and therapeutic resistance.

JMJD1A (also called lysine demethylase 3A [KDM3A]) belongs to the Jumonji C family of histone demethylases. It specifically removes the repressive mono- or di-methyl marks from histone H3 at lysine 9 and thus contributes to the activation of gene transcription. JMJD1A plays a key role in a variety of biological processes such as spermatogenesis, metabolism, sex determination, and stem cell activity. JMJD1A is upregulated in various types of cancers and can promote cancer development, progression, and therapeutic resistance. JMJD1A can epigenetically regulate the expression or activity of transcription factors such as c-Myc, androgen receptor (AR), estrogen receptor (ER), ß-catenin, and so on. Expression and activity of JMJD1A in cancer cells can be regulated at transcriptional, post-transcriptional, and post-translational levels. Targeting JMJD1A may repress the oncogenic transcription factors as a potential anticancer therapy.

A comparison of the influencing factors of chronic pain and quality of life between older Koreans and Korean-Americans with chronic pain: a correlational study.

BACKGROUND: Chronic pain is one of the most common health problems for older adults worldwide and is likely to result in lower quality of life. Living in a different culture may also influence chronic pain and quality of life in older adults. The purpose of this study was to explore how multifaceted elements affect chronic pain and quality of life in older Koreans living in Korea and in older Korean-Americans (KAs) living in the USA. METHODS: We conducted a secondary data analysis of data from 270 adults aged 65 years or over (138 Koreans and 132 KAs). We compared the effects of multifaceted elements on pain and quality of life by testing structural equation models (SEMs) for each group, using a maximum likelihood estimation and bootstrapping. RESULTS: SEMs for both Korean and KAs showed that age and depressive symptoms directly affected quality of life. The number of comorbidities and depressive symptoms had mediating effects on quality of life through chronic pain in both groups. In older Koreans only, perceived financial status directly affected quality of life. In older KAs only, sleep quality indirectly affected quality of life through chronic pain. CONCLUSION: The data showed that multimorbidity and depressive symptoms play critical roles for explaining chronic pain in older Koreans and KAs and ultimately negatively influence quality of life. Future intervention program to improve quality of life in older adults with chronic pain should consider the different cultural aspects affecting quality of life for Koreans and KAs.

Evaluating a theory-based intervention for improving eHealth literacy in older adults: a single group, pretest-posttest design.

BACKGROUND: The Internet is considered an important channel for providing health information to older adults. We developed an intervention to improve eHealth literacy in older adults according to the information-motivation-behavioral skills (IMB) theory and Intervention Mapping. This study aimed to analyze the effect of a developed intervention on information, motivation, behavioral skills, and behaviors related to eHealth information in older adults. METHODS: Forty-six older adults over the age of 65 were recruited from two senior welfare centers in a city in South Korea. We divided the participants into four groups and conducted one intervention per group from March to December 2019. One intervention consisted of 5 sessions and was performed once a week (2 h/1 time) for 5 weeks, culminating in a total lecture time of 10 h. One lecture instructor and two assistant instructors supported the participants in the computer practices. RESULTS: Participants' computer/web knowledge, perceived ease of use, perceived enjoyment, and attitude toward eHealth information showed statistically significant increases. The eHealth literacy efficacy score, searching performance score, and understanding score were also significantly increased. However, there was no significant difference in perceived usefulness. CONCLUSION: The application of the current theory-based methodology can improve the quality of research in eHealth literacy. Additionally, various interventions should be developed and continuously applied to improve eHealth literacy among older adults.

Internet health information education for older adults: A pilot study.

This study aimed to develop internet health information education program, and to explore the program's feasibility and preliminary effects. We made use of an intervention mapping approach and adopted as conceptual framework the information-motivation-behavioral skills model to develop the program. We evaluated the feasibility and the impact of the education program using a single-group pretest-posttest design using generalized equation estimation. Eleven older adults participated in the classes from January 25 to February 22, 2019. Each outcome of the behavioral theory-based components of the program-computer/Web knowledge (p < .001), attitude toward internet-based health information (p = .002), eHealth literacy score (p < .001), searching performance scores (p < .001), and level of understanding of internet-based health information (p = .002)-showed significant improvement immediately after the intervention. This pilot study reveals that a behavior theory-based education program for utilizing internet-based health information is an effective way to increase older adults' eHealth literacy.

Intra-Ethnic Differences in Chronic Pain and the Associated Factors: An Exploratory, Comparative Design.

PURPOSE: To describe and compare the levels of pain severity and pain interference, pain catastrophizing, and associated factors between elderly Koreans living in South Korea and Korean Americans living in the United States with chronic pain. METHODS: An exploratory, comparative design was used for this study. A total of 270 individuals (138 Koreans living in South Korea and 132 Korean Americans living in the United States), aged more than 65 years, with self-reported chronic pain, and defined as at least 3 months of persistent musculoskeletal pain, is included. Outcome variables were pain severity, pain interference, and pain catastrophizing. Multivariate linear regression was conducted to examine factors associated with the outcome variables. RESULTS: In multivariate analysis, Korean Americans had higher levels of pain severity and pain catastrophizing than Koreans. Depressive symptoms, sleep quality, and health-related quality of life were significant factors for pain severity, pain interference, and pain catastrophizing for both groups. Among those factors, health-related quality of life was the most significant factor for predicting pain severity and pain interference, whereas depressive symptoms were the most significant factor for predicting pain catastrophizing for both groups. CONCLUSIONS: Intra-ethnic differences in pain severity and pain catastrophizing were found between elderly Koreans living in South Korea and Korean Americans living in the United States. CLINICAL RELEVANCE: Because unfamiliar sociocultural and environmental factors may influence the pain responses, cultural differences and language barriers should be taken into account in pain research and management strategies for Asian immigrants in the United States. Psychological factors, including depressive symptoms, sleep quality, and health-related quality of life, should also be considered in chronic pain management for both elderly Koreans and Korean Americans.

Comparing Factors Associated With eHealth Literacy Between Young and Older Adults.

The purpose of the current study was to compare the factors associated with adults' eHealth literacy, which is vital for health consumers. A secondary data analysis was conducted with data collected from November 2017 to February 2018 for a project on the development of a Korean version of the eHealth Literacy Scale. Participants were recruited through an online survey for young adults (n = 210, mean age = 25.5 [SD = 4.7] years) and a face-to-face survey for older adults (n = 187, mean age = 73.2 [SD = 4.8] years). Hierarchical multiple regression analyses were used to analyze data and determine eHealth literacy predictors. Older adults held more positive attitudes toward internet health information than young adults (mean = 16.49 [SD = 2.54] and 17.04 [SD = 2.41], respectively; p = 0.029); however, eHealth literacy levels were comparable (mean = 30.50 [SD = 4.62] and 30.95 [SD = 4.17], respectively; p = 0.305). Attitude toward internet health information was a significant predictor of eHealth literacy in both groups, and age was only a predictor among young adults. These results elucidate predictors of eHealth literacy and inform strategies to improve eHealth literacy among young and older adults. [Journal of Gerontological Nursing, 46(8), 46-56.].

SUMOylation regulates polo-like kinase 1-interacting checkpoint helicase (PICH) during mitosis.

Mitotic SUMOylation has an essential role in faithful chromosome segregation in eukaryotes, although its molecular consequences are not yet fully understood. In Xenopus egg extract assays, we showed that poly(ADP-ribose) polymerase 1 (PARP1) is modified by SUMO2/3 at mitotic centromeres and that its enzymatic activity could be regulated by SUMOylation. To determine the molecular consequence of mitotic SUMOylation, we analyzed SUMOylated PARP1-specific binding proteins. We identified Polo-like kinase 1-interacting checkpoint helicase (PICH) as an interaction partner of SUMOylated PARP1 in Xenopus egg extract. Interestingly, PICH also bound to SUMOylated topoisomerase IIα (TopoIIα), a major centromeric small ubiquitin-like modifier (SUMO) substrate. Purified recombinant human PICH interacted with SUMOylated substrates, indicating that PICH directly interacts with SUMO, and this interaction is conserved among species. Further analysis of mitotic chromosomes revealed that PICH localized to the centromere independent of mitotic SUMOylation. Additionally, we found that PICH is modified by SUMO2/3 on mitotic chromosomes and in vitro. PICH SUMOylation is highly dependent on protein inhibitor of activated STAT, PIASy, consistent with other mitotic chromosomal SUMO substrates. Finally, the SUMOylation of PICH significantly reduced its DNA binding capability, indicating that SUMOylation might regulate its DNA-dependent ATPase activity. Collectively, our findings suggest a novel SUMO-mediated regulation of the function of PICH at mitotic centromeres.

Rod/Zw10 complex is required for PIASy-dependent centromeric SUMOylation.

SUMO conjugation of cellular proteins is essential for proper progression of mitosis. PIASy, a SUMO E3 ligase, is required for mitotic SUMOylation of chromosomal proteins, yet the regulatory mechanism behind the PIASy-dependent SUMOylation during mitosis has not been determined. Using a series of truncated PIASy proteins, we have found that the N terminus of PIASy is not required for SUMO modification in vitro but is essential for mitotic SUMOylation in Xenopus egg extracts. We demonstrate that swapping the N terminus of PIASy protein with the corresponding region of other PIAS family members abolishes chromosomal binding and mitotic SUMOylation. We further show that the N-terminal domain of PIASy is sufficient for centromeric localization. We identified that the N-terminal domain of PIASy interacts with the Rod/Zw10 complex, and immunofluorescence further reveals that PIASy colocalizes with Rod/Zw10 in the centromeric region. We show that the Rod/Zw10 complex interacts with the first 47 residues of PIASy which were particularly important for mitotic SUMOylation. Finally, we show that depletion of Rod compromises the centromeric localization of PIASy and SUMO2/3 in mitosis. Together, we demonstrate a fundamental mechanism of PIASy to localize in the centromeric region of chromosome to execute centromeric SUMOylation during mitosis.

PIASy mediates SUMO-2/3 conjugation of poly(ADP-ribose) polymerase 1 (PARP1) on mitotic chromosomes.

PIASy is a small ubiquitin-related modifier (SUMO) ligase that modifies chromosomal proteins in mitotic Xenopus egg extracts and plays an essential role in mitotic chromosome segregation. We have isolated a novel SUMO-2/3-modified mitotic chromosomal protein and identified it as poly(ADP-ribose) polymerase 1 (PARP1). PARP1 was robustly conjugated to SUMO-2/3 on mitotic chromosomes but not on interphase chromatin. PIASy promotes SUMOylation of PARP1 both in egg extracts and in vitro reconstituted SUMOylation assays. Through tandem mass spectrometry analysis of mitotically SUMOylated PARP1, we identified a residue within the BRCA1 C-terminal domain of PARP1 (lysine 482) as its primary SUMOylation site. Mutation of this residue significantly reduced PARP1 SUMOylation in egg extracts and enhanced the accumulation of species derived from modification of secondary lysine residues in assays using purified components. SUMOylation of PARP1 did not alter in vitro PARP1 enzyme activity, poly-ADP-ribosylation (PARylation), nor did inhibition of SUMOylation of PARP1 alter the accumulation of PARP1 on mitotic chromosomes, suggesting that SUMOylation regulates neither the intrinsic activity of PARP1 nor its localization. However, loss of SUMOylation increased PARP1-dependent PARylation on isolated chromosomes, indicating SUMOylation controls the capacity of PARP1 to modify other chromatin-associated proteins.

Psychometric comparisons of measures of eHealth literacy using a sample of Korean older adults.

AIMS: This study aimed to compare the psychometric properties of two measures of eHealth literacy, namely, the Korean versions of the Digital Health Literacy Instrument (K-DHLI) and eHealth Literacy Scale (K-eHEALS), among older adults in South Korea. BACKGROUND: Given the usefulness of eHealth information, measures of eHealth literacy have been developed. It is necessary to examine the validity of such tools among older adults who are likely to experience difficulties in using eHealth resources. METHODS: A validation study was conducted using the secondary data of 180 older adults in South Korea. Two weeks after they had responded to the K-DHLI and K-eHEALS, 89 of them completed the assessments a second time so that the assessments' test-retest reliability could be examined. Using the collected data, their reliability (i.e. internal consistency, test-retest reliability) and validity (i.e. construct validity and criterion validity) were examined. RESULTS: Both tools demonstrated satisfactory internal consistency (α ≥ 0.90, item-total correlation coefficients = .39-.76) as well as good test-retest reliability with intraclass correlation coefficients .77 and .84, respectively. The 21 items of the K-DHLI loaded onto five factors, which accounted for 71% of the variance. The 10 items of the K-eHEALS loaded onto a single factor, which explained 58% of the total variance. The scores of both tools were strongly correlated (r = .63) and positively related to attitudes towards internet health information and subjective health status (r = .23-.50). CONCLUSIONS: The findings suggest that the K-DHLI and K-eHEALS are reliable and valid tools that can be used to assess the utilisation of eHealth resources by older adults. IMPLICATIONS FOR PRACTICE: The findings can help healthcare providers choose a suitable measure of eHealth literacy when working with older adults.

The Effect of Pain Catastrophizing on Depression among Older Korean Adults with Chronic Pain: The Mediating Role of Chronic Pain Interference and Sleep Quality.

Pain catastrophizing is a notable concept associated with change in chronic pain interference and depression. Sleep quality is also one of the important factors affecting geriatric depression. This study examined the mediating effects of chronic pain interference and sleep quality on the relationship between pain catastrophizing and depression. This study is a secondary data analysis that analyzed a total of 138 older Korean adults with chronic pain. The participants were selected from a single elderly daycare center in a city in South Korea. Also, the multiple regression analysis and PROCESS macro with bootstrapping were used. The results revealed that chronic pain interference and sleep quality mediated the relationship between pain catastrophizing and depression, respectively. Furthermore, chronic pain interference and sleep quality sequentially and dually mediated the effect of pain catastrophizing on depression. In the management of depression in the elderly, persistent complaints of pain should not be disregarded, irrespective of the intensity of their chronic pain. Psychological intervention is needed to alleviate negative thoughts about chronic pain and to increase the ability to cope with chronic pain. In addition, it is important to assess sleep patterns and to develop interventions to improve sleep quality, because depression in the elderly could appear as a symptom of a sleep problems.

Diabetes self-care behaviors in adults with disabilities: A systematic review.

AIM: The integrated evidence on diabetes self-care behaviors in people with a disability is not commensurate with the growing number of people with both diabetes and a disability. This study aims to identify factors influencing self-care behaviors in adults with diabetes and a disability based on a thorough review of the current evidence. METHODS: This review followed the Cochrane guidelines for systematic review research and complies with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis. To find eligible articles, five electronic databases-PubMed, Embase, CINAHL, Psych-articles, and the Cochrane Library-were searched, from the beginning of the chronological period covered by each database to June 2017. Four researchers independently conducted study selections, extracted data, and assessed the data quality. RESULTS: Twenty studies were reviewed to identify barriers to and facilitators of diabetes self-care behaviors. For people with developmental disabilities, the most prominent facilitator of self-care behaviors was the support they received for the behaviors. For people with visual impairments, that facilitator was the use of helpful assistive devices that take advantage of another sense. The main barriers to self-care behaviors were mobility limitation for people with physical disabilities and lack of accessibility for people with visual impairments. CONCLUSIONS: This review has identified barriers to and facilitators of diabetes self-care behaviors by type of disability. Healthcare services need to be tailored to these facilitators and barriers, and differentiated by type of disability.

Performance evaluation of quantitative SPECT/CT using NEMA NU 2 PET methodology.

Although PET is routinely evaluated using NEMA NU2 as standard in the clinic, standard methodology for evaluating the performance of quantitative SPECT systems has not been established. In this study, the quantitative performance of the Symbia Intevo SPECT/CT was evaluated for two common isotopes (99mTc, 177Lu) and benchmarked against the performance of a PET/CT. A further aim was to demonstrate the utility of adapting NEMA NU2 PET measurements to SPECT. In addition, dead-time and resolution recovery were evaluated to provide more complete system evaluations. Spatial resolution of the SPECT system at 1 cm from the center in the transverse direction was 13.1 mm and 22.4 mm for 99mTc and 177Lu respectively, compared with 4.3 mm (18F) and 5.8 mm (68Ga) for PET. Sensitivity at the center of the FoV was 119 cps MBq-1 and 48 cps MBq-1 (99mTc, 177Lu) for SPECT and 9632 cps MBq-1 and 8216 cps MBq-1 (18F, 68Ga) for PET. Scatter fraction was 0.25 and 0.36 (99mTc, 77Lu) for SPECT and 0.32 and 0.29 (18F, 68Ga) for PET. Contrast recovery coefficient in the largest spheres was 0.79 and 0.65 (99mTc, 177Lu) for SPECT, 1.00 and 0.97 (18F, 68Ga) for PET and the background variability was 2.7%, 6.5% (99mTc, 177Lu), 1.5% and 1.6% (18F, 68Ga), respectively. Partial volume effect was evaluated using the NEMA IQ phantom with six sphere inserts (diameter: 37 mm, 28 mm, 22 mm, 17 mm, 13 mm and 10 mm). Full contrast recovery was reached with the 17 mm for 18F, while SPECT did not reach full recovery for any sphere. Count rate losses were 2% for 99mTc at 1 GBq and 11% for 177Lu at 8.5 GBq which are well below the typical activities for clinical applications. We concluded NEMA NU2 methodology can be easily adapted to SPECT/CT as a routine quality assurance procedure in the clinic.

A Comparison of 2D and 3D Kidney Absorbed Dose Measures in Patients Receiving 177Lu-DOTATATE.

OBJECTIVES: To investigate and compare quantitative accuracy of kidney absorbed dose measures made from both 2D and 3D imaging in patients receiving 177Lu-DOTATATE (Lutate) for treatment of neuroendocrine tumours (NETs). METHODS: Patients receiving Lutate therapy underwent both whole body planar imaging and SPECT/CT imaging over the kidneys at time points 0.5, 4, 24, and 96-120 hours after injection. Planar data were corrected for attenuation using transmission data, and were converted to units of absolute activity via two methods, using either a calibration standard in the field of view or relative to pre-voiding image total counts. Hand drawn regions of interest were used to generate time activity curves and kidney absorbed dose estimates in OLINDA-EXM. Fully quantitative SPECT data were generated using CT-derived corrections for both scatter and attenuation, before correction for dead time and application of a camera specific sensitivity factor to convert data to units of absolute activity. Volumes of interest were defined for kidney using the co-registered x-ray CT, before time activity curves and absorbed dose measures were generated in OLINDA-EXM, both with and without corrections made to the model for patient specific kidney volumes. Quantitative SPECT data were also used to derive dose maps through dose kernel convolution (DKC), which was treated as the gold standard. RESULTS: A total of 50 studies were analysed, corresponding to various cycles of treatment from 21 patients. Planar absorbed dose estimates were consistently higher than SPECT derived estimates by, on average, a factor of 3. CONCLUSION: Quantitative SPECT is considered the gold standard approach for organ specific dosimetry however often relies on in house software. As such planar methods for estimating absorbed dose are much more widely available, and in particular, are often the only source of reference in previously published data. For the case of Lutate dosimetry, planar measures may lead to a three-fold increase in measures of kidney absorbed dose.

Feasibility and accuracy of single time point imaging for renal dosimetry following 177Lu-DOTATATE ('Lutate') therapy.

BACKGROUND: This study aims to assess both feasibility and accuracy of renal dosimetry imaging protocols in patients receiving Lutate therapy for neuroendocrine tumours (NETs), when data acquisition over multiple days is not possible on all cycles. METHOD: Patients who had received a full 4 cycles of Lutate therapy with complete imaging at each cycle were included. Imaging consisted of quantitative SPECT/CT of the kidneys at 4, 24 and 96-120 h post injection. Renal absorbed dose was calculated for each data set, and in addition, five alternative methods were explored for comparison. Method 1: a patient average clearance time (t1/2 average) derived from the first half of contributing patient data was used to estimate absorbed dose for subsequent patients based on 4 h imaging alone; method 2: t1/2 average was applied to subsequent patients on 24 h imaging alone; method 3: a patient-specific clearance rate (t1/2 patient) was determined from complete image data of cycle 1 and applied subsequently to remaining cycles using 4 h image data alone; method 4: t1/2 patient was applied to 24 h imaging alone in subsequent cycles; method 5: the 120 h data was estimated on subsequent cycles based on the cycle 1 fraction of injected activity (%IA) at 24 and 120 h. RESULTS: Twenty treatments from 18 patients, resulting in 80 cycles of therapy, were analysed. The measured average renal absorbed dose per cycle of treatment was 0.38 ± 0.19 Gy/GBq when derived from full imaging data. The use of t1/2 average applied to a single time point led to large deviations of dose estimates from true values (on average 59% and 30%, when using 4 h data and 24 h data, respectively). The use of complete image data on cycle 1 and the derivation of t1/2 patient led to improved dose estimates, with an average deviation from true values of 13% and 2% when using 4 h data only and 24 h data only, respectively. The use of a 120 h %IA derived from cycle 1 led to an average deviation from true dose estimates of 14%. CONCLUSION: In instances where demands on both patients and facilities make multiple time point data acquisition impractical, renal dosimetry is best derived through complete imaging at cycle 1 only followed by a single 24 h imaging time point on subsequent cycles, assuming no significant changes in renal function during the time course of therapy.

Comparison of radiobiological parameters for 90Y radionuclide therapy (RNT) and external beam radiotherapy (EBRT) in vitro.

BACKGROUND: Dose rate variation is a critical factor affecting radionuclide therapy (RNT) efficacy. Relatively few studies to date have investigated the dose rate effect in RNT. Therefore, the aim of this study was to benchmark 90Y RNT (at different dose rates) against external beam radiotherapy (EBRT) in vitro and compare cell kill responses between the two irradiation processes. RESULTS: Three human colorectal carcinoma (CRC) cell lines (HT29, HCT116, SW48) were exposed to 90Y doses in the ranges 1-10.4 and 6.2-62.3 Gy with initial dose rates of 0.013-0.13 Gy/hr (low dose rate, LDR) and 0.077-0.77 Gy/hr (high dose rate, HDR), respectively. Results were compared to a 6-MV photon beam doses in the range from 1-9 Gy with constant dose rate of 277 Gy/hr. The cell survival parameters from the linear quadratic (LQ) model were determined. Additionally, Monte Carlo simulations were performed to calculate the average dose, dose rate and the number of hits in the cell nucleus. For the HT29 cell line, which was the most radioresistant, the α/ß ratio was found to be ≈ 31 for HDR-90Y and ≈ 3.5 for EBRT. LDR-90Y resulting in insignificant cell death compared to HDR-90Y and EBRT. Simulation results also showed for LDR-90Y, for doses ≲ 3 Gy, the average number of hits per cell nucleus is ≲ 2 indicating insufficiently delivered lethal dose. For 90Y doses [Formula: see text] 3 Gy the number of hits per nucleus decreases rapidly and falls below ≈ 2 after ≈ 5 days of incubation time. Therefore, our results demonstrate that LDR-90Y is radiobiologically less effective than EBRT. However, HDR-90Y at ≈ 56 Gy was found to be radiobiologically as effective as acute ≈ 8 Gy EBRT. CONCLUSION: These results demonstrate that the efficacy of RNT is dependent on the initial dose rate at which radiation is delivered. Therefore, for a relatively long half-life radionuclide such as 90Y, a higher initial activity is required to achieve an outcome as effective as EBRT.

SUMOylation of the C-terminal domain of DNA topoisomerase IIα regulates the centromeric localization of Claspin.

DNA topoisomerase II (TopoII) regulates DNA topology by its strand passaging reaction, which is required for genome maintenance by resolving tangled genomic DNA. In addition, TopoII contributes to the structural integrity of mitotic chromosomes and to the activation of cell cycle checkpoints in mitosis. Post-translational modification of TopoII is one of the key mechanisms by which its broad functions are regulated during mitosis. SUMOylation of TopoII is conserved in eukaryotes and plays a critical role in chromosome segregation. Using Xenopus laevis egg extract, we demonstrated previously that TopoIIα is modified by SUMO on mitotic chromosomes and that its activity is modulated via SUMOylation of its lysine at 660. However, both biochemical and genetic analyses indicated that TopoII has multiple SUMOylation sites in addition to Lys660, and the functions of the other SUMOylation sites were not clearly determined. In this study, we identified the SUMOylation sites on the C-terminal domain (CTD) of TopoIIα. CTD SUMOylation did not affect TopoIIα activity, indicating that its function is distinct from that of Lys660 SUMOylation. We found that CTD SUMOylation promotes protein binding and that Claspin, a well-established cell cycle checkpoint mediator, is one of the SUMOylation-dependent binding proteins. Claspin harbors 2 SUMO-interacting motifs (SIMs), and its robust association to mitotic chromosomes requires both the SIMs and TopoIIα-CTD SUMOylation. Claspin localizes to the mitotic centromeres depending on mitotic SUMOylation, suggesting that TopoIIα-CTD SUMOylation regulates the centromeric localization of Claspin. Our findings provide a novel mechanistic insight regarding how TopoIIα-CTD SUMOylation contributes to mitotic centromere activity.

SUMOylation of Psmd1 controls Adrm1 interaction with the proteasome.

SUMOylation is the covalent conjugation of SUMO polypeptides to cellular target proteins. Psmd1 is a subunit of the proteasomal 19S regulatory particle that acts as a docking site for Adrm1, another proteasome subunit that recruits ubiquitinated substrates for proteolysis. Here, we show that the SUMO deconjugating enzyme xSENP1 specifically interacts with Psmd1 and that disruption of xSENP1 targeting delays mitotic exit. Psmd1 becomes SUMOylated through the action of the SUMO E3 enzyme PIASy. We mapped SUMOylation sites within Psmd1 and found that SUMOylation of a critical lysine immediately adjacent to the Adrm1-binding domain regulates the association of Adrm1 with Psmd1. Together, our findings suggest that the interaction of Psmd1 with Adrm1 is controlled by SUMOylation in a manner that may alter proteasome composition and function. These findings demonstrate a mechanism for regulation of ubiquitin-mediated protein degradation by ubiquitin-like proteins of the SUMO family.