Effect of SOS-induced Pol II, Pol IV, and Pol V DNA polymerases on UV-induced mutagenesis and MFD repair in Escherichia coli cells

Irradiation of organisms with UV light produces genotoxic and mutagenic lesions in DNA. Replication through these lesions (translesion DNA synthesis, TSL) in Escherichia coli requires polymerase V (Pol V) and polymerase III (Pol III) holoenzyme. However, some evidence indicates that in the absence of Pol V, and with Pol III inactivated in its proofreading activity by the mutD5 mutation, efficient TSL takes place. The aim of this work was to estimate the involvement of SOS-inducible DNA polymerases, Pol II, Pol IV and Pol V, in UV mutagenesis and in mutation frequency decline (MFD), a mechanism of repair of UV-induced damage to DNA under conditions of arrested protein synthesis. Using the argE3-->Arg(+) reversion to prototrophy system in E. coli AB1157, we found that the umuDC-encoded Pol V is the only SOS-inducible polymerase required for UV mutagenesis, since in its absence the level of Arg(+) revertants is extremely low and independent of Pol II and/or Pol IV. The low level of UV-induced Arg(+) revertants observed in the AB1157mutD5DumuDC strain indicates that under conditions of disturbed proofreading activity of Pol III and lack of Pol V, UV-induced lesions are bypassed without inducing mutations. The presented results also indicate that Pol V may provide substrates for MFD repair; moreover, we suggest that only those DNA lesions which result from umuDC-directed UV mutagenesis are subject to MFD repair.     

Thermal proteome profiling of breast cancer cells reveals proteasomal activation by CDK4/6 inhibitor palbociclib

Palbociclib is a CDK4/6 inhibitor approved for metastatic estrogen receptor‐positive breast cancer. In addition to G1 cell cycle arrest, palbociclib treatment results in cell senescence, a phenotype that is not readily explained by CDK4/6 inhibition. In order to identify a molecular mechanism responsible for palbociclib‐induced senescence, we performed thermal proteome profiling of MCF7 breast cancer cells. In addition to affecting known CDK4/6 targets, palbociclib induces a thermal stabilization of the 20S proteasome, despite not directly binding to it. We further show that palbociclib treatment increases proteasome activity independently of the ubiquitin pathway. This leads to cellular senescence, which can be counteracted by proteasome inhibitors. Palbociclib‐induced proteasome activation and senescence is mediated by reduced proteasomal association of ECM29. Loss of ECM29 activates the proteasome, blocks cell proliferation, and induces a senescence‐like phenotype. Finally, we find that ECM29 mRNA levels are predictive of relapse‐free survival in breast cancer patients treated with endocrine therapy. In conclusion, thermal proteome profiling identifies the proteasome and ECM29 protein as mediators of palbociclib activity in breast cancer cells.     

Treatment with sorafenib in advanced thyroid cancer - a case report

Papillary thyroid cancer (PTC) usually has a good prognosis. The treatment, including total thyroidectomy and complementary radioiodine (RAI) therapy, gives complete remission in 90% of patients. However, in 10% of subjects with metastatic disease, the prognosis is poor. In the group of patients with disease progression and no 131I uptake, searching for new therapeutic modalities before all tyrosine kinase inhibitors and other antiangiogenic agents is necessary. The study presents the case of a 55-year-old male with advanced PTC /pT3mNxMo/ diagnosed in 1993. Primary treatment by total thyroidectomy and 131I ablation led to complete remission. In 2000 local as well as lymph node recurrence was diagnosed and successively treated by surgery. In 2006 an increasing serum thyroglobulin level was noted and a single lung metastasis was diagnosed and operated on. In 2007 new foci in CNS and vertebral column with no 131I uptake were stated. Further progression (bones, CNS, and pterygoid muscle) was confirmed by PET-CT. The patient underwent neurosurgical metastasectomy twice and palliative CNS and vertebra's radiotherapy. Liver metastases were diagnosed in 2009. Treatment with increasing doses of thalidomide (up to 800 mg/d) was administered for 3 months with a good tolerance; however, the therapy was withdrawn due to cancer progression. Next, sorafenib (800 mg/d) was given for 16 weeks. Radiological examination performed after 16 weeks confirmed stable disease, whereas 2 months later, after sorafenib withdrawal due to lack of treatment possibility, further progression was observed. Metronomic chemotherapy with Adriamycin was instituted which gave disease stabilization for 6 months. The patient died with advanced disseminated disease due to pulmonary embolism. We present this case to document no adverse effects of therapy with sorafenib in a patient with brain DTC metastases. Sorafenib therapy was only short-term, but no progression occurred in this time.     

Application of microsatellite markers developed for arvicoline species in a population genetic study of the root vole <Emphasis Type="Italic">Microtus oeconomus</Emphasis>

Using a root vole Microtus oeconomus (Pallas, 1776) population in NE Poland we applied 31 microsatellite markers previously developed for root voles and closely related species, with the aim to improve the population genetic tools in this species. Here we present 16 polymorphic microsatellite markers grouped into four sets suitable for simultaneous amplification and genetically sex identification in M. oeconomus. The number of alleles per locus in 227 individuals varied from 7 to 26 with a low frequency of null alleles, expected heterozygosity ranged from 0.758 to 0.927, and observed heterozygosity from 0.722 to 0.947. Two loci showed significant deviation from Hardy-Weinberg equilibrium (p<0.05) and all loci showed independent inheritance. We expect these markers to be useful for studies of genetic population structure and kinship of M. oeconomus populations.     

Copulatory behaviour of the bank voleMyodes glareolus: matings with one and two males do not make a difference

In promiscuous species in which females mate with more than one male during oestrus, males may increase their sperm expenditure or change their copulatory behaviour in response to the risk of sperm competition. I used an experimental approach to investigate the pattern of copulatory behaviour of the bank voleMyodes glareolus Schreber, 1780 depending on whether the female mated with one or two males. The work showed that the copulatory period of the bank vole lasted about 80 minutes and consisted of 4–5 ejaculatory series, with multiple intromissions preceding ejaculation. There were no significant changes in number of intromissions across the first four ejaculatory series, but I did find a relationship between number of intromissions and first ejaculation latency; also, ejaculation latencies grew shorter as the ejaculatory series proceeded. Litter size did not differ significantly between females that mated with one male and those mating with two, nor did the reproductive success of males that mated with the same female. Mating with an oestrus female appears to be advantageous for bank vole males even if they mate as the second one, and the risk of sperm competition did not trigger changes in male copulatory behaviour. The similar durations of the copulatory period and patterns of change of ejaculation latencies during copulations with one and two males point to the role of the female in temporal copulatory behaviour of the bank vole.     

Maintenance of genetic variation and moderate differentiation among populations under sex-biased dispersal in the common voleMicrotus arvalis in patchy habitats

We present a microgeographic analysis of 34 allozyme loci and the control region of mitochondrial DNA (mtDNA) in the common voleMicrotus arvalis (Pallas, 1779), performed to assess the effects of environmental heterogeneity on the distribution of genetic variation among populations in the Biebrza river valley, NE Poland. The common vole occurs there in two types of habitat: open grassland and pastures around the valley (GP populations); and abandoned fields on small hills isolated by wetlands (SH populations). No significant genetic differences were found between SH and GP populations with respect to allelic richness, nor average observed and expected heterozygosities. The average genetic differentiation at allozyme loci among the SH populations was significantly lower (F _ST =0.066) than among the GP populations located around the Biebrza valley (F _ST =0.112), and an isolation by distance pattern was detected (r=0.26,pr<0.05). Mitochondrial DNA differentiation among the GP populations was great (F _ST =0.357,p<0.01), indicating that female dispersal was 4.4–6.5 times lower than for males. Our results and reviewed published data onM. arvalis dispersal suggest that common vole dispersal in patchy natural and semi-natural habitats is male-biased and could generate moderate population divergence, with relatively high levels of genetic variation retained within populations.     

Application of multiplex FISH, CGH and MSSCP techniques for cytogenetic and molecular analysis of transitional cell carcinoma (TCC) cells in voided urine specimens

Multiplex FISH (UroVysion), Comparative Genomic Hybridization (CGH), and Multitemperature Single-Strand Conformation Polymorphism (MSSCP) were applied for non-invasive diagnosis and prognosis of bladder cancer. The UroVysion test was positive in 80% of patients with pT1 and in 100% of patients with either pT2 or pT3 tumours. Tumours with pT3T4 stages were characterized by high numbers of chromosomal imbalances, detected by CGH. The mutation of the p53 gene was detected in 16% of patients, but only in those with pT2 or pT3 tumours.     

Calsyntenin-1 docks vesicular cargo to kinesin-1

We identified a direct interaction between the neuronal transmembrane protein calsyntenin-1 and the light chain of Kinesin-1 (KLC1). GST pulldowns demonstrated that two highly conserved segments in the cytoplasmic domain of calsyntenin-1 mediate binding to the tetratricopeptide repeats of KLC1. A complex containing calsyntenin-1 and the Kinesin-1 motor was isolated from developing mouse brain and immunoelectron microscopy located calsyntenin-1 in association with tubulovesicular organelles in axonal fiber tracts. In primary neuronal cultures, calsyntenin-1-containing organelles were aligned along microtubules and partially colocalized with Kinesin-1. Using live imaging, we showed that these organelles are transported along axons with a velocity and processivity typical for fast axonal transport. Point mutations in the two kinesin-binding segments of calsyntenin-1 significantly reduced binding to KLC1 in vitro, and vesicles bearing mutated calsyntenin-1 exhibited a markedly altered anterograde axonal transport. In summary, our results indicate that calsyntenin-1 links a certain type of vesicular and tubulovesicular organelles to the Kinesin-1 motor.     

Adaptation to P element transposon invasion in Drosophila melanogaster

Transposons evolve rapidly and can mobilize and trigger genetic instability. Piwi-interacting RNAs (piRNAs) silence these genome pathogens, but it is unclear how the piRNA pathway adapts to invasion of new transposons. In Drosophila, piRNAs are encoded by heterochromatic clusters and maternally deposited in the embryo. Paternally inherited P element transposons thus escape silencing and trigger a hybrid sterility syndrome termed P-M hybrid dysgenesis. We show that P-M hybrid dysgenesis activates both P elements and resident transposons and disrupts the piRNA biogenesis machinery. As dysgenic hybrids age, however, fertility is restored, P elements are silenced, and P element piRNAs are produced de novo. In addition, the piRNA biogenesis machinery assembles, and resident elements are silenced. Significantly, resident transposons insert into piRNA clusters, and these new insertions are transmitted to progeny, produce novel piRNAs, and are associated with reduced transposition. P element invasion thus triggers heritable changes in genome structure that appear to enhance transposon silencing.