MYC Oncogene Contributions to Release of Cell Cycle Brakes

Promotion of the cell cycle is a major oncogenic mechanism of the oncogene c-MYC (MYC). MYC promotes the cell cycle by not only activating or inducing cyclins and CDKs but also through the downregulation or the impairment of the activity of a set of proteins that act as cell-cycle brakes. This review is focused on the role of MYC as a cell-cycle brake releaser i.e., how MYC stimulates the cell cycle mainly through the functional inactivation of cell cycle inhibitors. MYC antagonizes the activities and/or the expression levels of p15, ARF, p21, and p27. The mechanism involved differs for each protein. p15 (encoded by CDKN2B) and p21 (CDKN1A) are repressed by MYC at the transcriptional level. In contrast, MYC activates ARF, which contributes to the apoptosis induced by high MYC levels. At least in some cells types, MYC inhibits the transcription of the p27 gene (CDKN1B) but also enhances p27's degradation through the upregulation of components of ubiquitin ligases complexes. The effect of MYC on cell-cycle brakes also opens the possibility of antitumoral therapies based on synthetic lethal interactions involving MYC and CDKs, for which a series of inhibitors are being developed and tested in clinical trials.The work in the laboratory of the authors is funded by grant SAF2017-88026-R from MINECO, Spanish Government, to J.L. and M.D.D., L.G.-G. was recipient of a fellowship from the FPI program from MINECO. The funding was co-sponsored by FEDER program from European Unio

Heteropolymeric Triplex-Based Genomic Assay® to Detect Pathogens or Single-Nucleotide Polymorphisms in Human Genomic Samples

Human genomic samples are complex and are considered difficult to assay directly without denaturation or PCR amplification. We report the use of a base-specific heteropolymeric triplex, formed by native duplex genomic target and an oligonucleotide third strand probe, to assay for low copy pathogen genomes present in a sample also containing human genomic duplex DNA, or to assay human genomic duplex DNA for Single Nucleotide Polymorphisms (SNP), without PCR amplification. Wild-type and mutant probes are used to identify triplexes containing FVL G1691A, MTHFR C677T and CFTR mutations. The specific triplex structure forms rapidly at room temperature in solution and may be detected without a separation step. YOYO-1, a fluorescent bis-intercalator, promotes and signals the formation of the specific triplex. Genomic duplexes may be assayed homogeneously with single base pair resolution. The specific triple-stranded structures of the assay may approximate homologous recombination intermediates, which various models suggest may form in either the major or minor groove of the duplex. The bases of the stable duplex target are rendered specifically reactive to the bases of the probe because of the activity of intercalated YOYO-1, which is known to decondense duplex locally 1.3 fold. This may approximate the local decondensation effected by recombination proteins such as RecA in vivo. Our assay, while involving triplex formation, is sui generis, as it is not homopurine sequence-dependent, as are “canonical triplexes”. Rather, the base pair-specific heteropolymeric triplex of the assay is conformation-dependent. The highly sensitive diagnostic assay we present allows for the direct detection of base sequence in genomic duplex samples, including those containing human genomic duplex DNA, thereby bypassing the inherent problems and cost associated with conventional PCR based diagnostic assays

ERK1/2 MAP kinases promote cell cycle entry by rapid, kinase-independent disruption of retinoblastoma–lamin A complexes

When in the nucleus, ERK1/2 dislodges the retinoblastoma protein from lamin A, facilitating its rapid phosphorylation

Increased variability in ApcMin/+ intestinal tissue can be measured with microultrasound

Altered tissue structure is a feature of many disease states and is usually measured by microscopic methods, limiting analysis to small areas. Means to rapidly and quantitatively measure the structure and organisation of large tissue areas would represent a major advance not just for research but also in the clinic. Here, changes in tissue organisation that result from heterozygosity in Apc, a precancerous situation, are comprehensively measured using microultrasound and three-dimensional high-resolution microscopy. Despite its normal appearance in conventionally examined cross-sections, both approaches revealed a significant increase in the variability of tissue organisation in Apc heterozygous tissue. These changes preceded the formation of aberrant crypt foci or adenoma. Measuring these premalignant changes using microultrasound provides a potential means to detect microscopically abnormal regions in large tissue samples, independent of visual examination or biopsies. Not only does this provide a powerful tool for studying tissue structure in experimental settings, the ability to detect and monitor tissue changes by microultrasound could be developed into a powerful adjunct to screening endoscopy in the clinic

Cyclin-Dependent Kinase Activity Controls the Onset of the HCMV Lytic Cycle

The onset of human cytomegalovirus (HCMV) lytic infection is strictly synchronized with the host cell cycle. Infected G0/G1 cells support viral immediate early (IE) gene expression and proceed to the G1/S boundary where they finally arrest. In contrast, S/G2 cells can be infected but effectively block IE gene expression and this inhibition is not relieved until host cells have divided and reentered G1. During latent infection IE gene expression is also inhibited, and for reactivation to occur this block to IE gene expression must be overcome. It is only poorly understood which viral and/or cellular activities maintain the block to cell cycle or latency-associated viral IE gene repression and whether the two mechanisms may be linked. Here, we show that the block to IE gene expression during S and G2 phase can be overcome by both genotoxic stress and chemical inhibitors of cellular DNA replication, pointing to the involvement of checkpoint-dependent signaling pathways in controlling IE gene repression. Checkpoint-dependent rescue of IE expression strictly requires p53 and in the absence of checkpoint activation is mimicked by proteasomal inhibition in a p53 dependent manner. Requirement for the cyclin dependent kinase (CDK) inhibitor p21 downstream of p53 suggests a pivotal role for CDKs in controlling IE gene repression in S/G2 and treatment of S/G2 cells with the CDK inhibitor roscovitine alleviates IE repression independently of p53. Importantly, CDK inhibiton also overcomes the block to IE expression during quiescent infection of NTera2 (NT2) cells. Thus, a timely block to CDK activity not only secures phase specificity of the cell cycle dependent HCMV IE gene expression program, but in addition plays a hitherto unrecognized role in preventing the establishment of a latent-like state

Myc and cell cycle control

Soon after the discovery of the Myc gene (c-Myc), it became clear thatMyc expression levels tightly correlate to cell proliferation. The entry in cell cycle of quiescent cells upon Myc enforced expression has been described in manymodels. Also, the downregulation or inactivation ofMyc results in the impairment of cell cycle progression. Given the frequent deregulation of Myc oncogene in human cancer it is important to dissect out the mechanisms underlying the role ofMyc on cell cycle control. Several parallel mechanisms account forMyc-mediated stimulation of the cell cycle. First,most of the critical positive cell cycle regulators are encoded by genes induced byMyc. These Myc target genes include Cdks, cyclins and E2F transcription factors. Apart from its direct effects on the transcription, Myc is able to hyperactivate cyclin/Cdk complexes through the induction of Cdk activating kinase (CAK) and Cdc25 phosphatases. Moreover, Myc antagonizes the activity of cell cycle inhibitors as p21 and p27 through different mechanisms. Thus, Myc is able to block p21 transcription or to induce Skp2, a protein involved in p27 degradation. Finally, Myc induces DNA replication by binding to replication origins and by upregulating genes encoding proteins required for replication initiation. Myc also regulates genes involved in the mitotic control. A promising approach to treat tumors with deregulated Myc is the synthetic lethality based on the inhibition of Cdks. Thus, the knowledge of the Myc-dependent cell cycle regulatory mechanisms will help to discover new therapeutic approaches directed against malignancies with deregulated Myc. This article is part of a Special Issue entitled: Myc proteins in cell biology and pathology.The work in the laboratory of the authors is funded by grants SAF11-23796 from Spanish Ministry of Industry and Innovation, and ISCIII-RETIC RD12/0036/0033 from Spanish Ministry of Health to JL, and FIS 11/00397 to MDD. GB is recipient of a fellowship form the FPI Program. We apologize to colleagues whose work has not been cited in the form of their original papers but in reviews and whose work has not been discussed due to space limitations or unintentional omission

Targets of wnt/ß-catenin transcription in penile carcinoma

Penile squamous cell carcinoma (PeCa) is a rare malignancy and little is known regarding the molecular mechanisms involved in carcinogenesis of PeCa. The Wnt signaling pathway, with the transcription activator ß-catenin as a major transducer, is a key cellular pathway during development and in disease, particularly cancer. We have used PeCa tissue arrays and multi-fluorophore labelled, quantitative, immunohistochemistry to interrogate the expression of WNT4, a Wnt ligand, and three targets of Wnt-ß-catenin transcription activation, namely, MMP7, cyclinD1 (CD1) and c-MYC in 141 penile tissue cores from 101 unique samples. The expression of all Wnt signaling proteins tested was increased by 1.6 to 3 fold in PeCa samples compared to control tissue (normal or cancer adjacent) samples (p<0.01). Expression of all proteins, except CD1, showed a significant decrease in grade II compared to grade I tumors. High magnification, deconvolved confocal images were used to measure differences in co-localization between the four proteins. Significant (p<0.04-0.0001) differences were observed for various permutations of the combinations of proteins and state of the tissue (control, tumor grades I and II). Wnt signaling may play an important role in PeCa and proteins of the Wnt signaling network could be useful targets for diagnosis and prognostic stratification of disease

Semantics of emotion words in Latvian web: differences between types of blogs

Bakalaura darba mērķis ir apskatīt dažādu emociju vārdu semantiku latviskajā tīmekļa vidē esošajos dažādu kategoriju blogos. Mērķa sasniegšanai tiks izveidots valodas korpuss, kas sastāv no latviešu valodā pieejamajiem dažādu blogu ierakstiem. Apskatot dažādu emociju modeļu piedāvātās emocijas tiks izvēlēti dažādi emociju vārdi, kuru semantika tiks apskatīta izveidotā valodas korpusa apakškorpusos. Salīdzinot emociju vārdu semantiku tiks apskatīti vārda konkordances saraksti katrā no izvēlētajiem apakškorpusiem. Darba rezultātā tiks noskaidrots vai emociju vārdu nozīme dažādu tipu blogos atšķiras. Tiks izstrādāti daži rīki, kas paredzēti atvieglot valodas korpusa izveidi izmantojot tīmekļa materiālus. Paredzēts izstrādāt tīmekļa vietni valodas korpusu glabāšanai, kā arī biežuma un konkordances sarakstu veidošanai.The purpse of this Bachelor’s thesis is to research the semantics of emotion words in different types of blogs available in latvian web. To achieve it a language corpus, consisting of different blogs in Latvian, will be created. Multiple emotion words will be chosen after reviewing differnet models of emotions. The semantics of these words will be researched in the sub-corpora of the corpora created. When comparing the semantics of the emotion words concordance list for each sub-corpora will be reviewed. As a result we will find out whether the semantics of emotion words differs in different types of blogs. Multiple tools intended to ease the creation of language corpora from web materials will be created. A web page intended to store and provide word frequency and concordance lists will be created as well

Automatization of tests for functions of radio studio control system

Kvalifikācijas darba “Radio studijas vadības sistēmas funkciju testu automatizācija” mērķis ir izstrādāt automatizētos testus radio studijas vadības sistēmas audio pirmavotu profilu iestatījumu pārbaudei. Darba rezultātā tiek nodrošināta kopējās radio studijas vadības sistēmas noteiktas daļas funkcionālo testu automatizācija, kas atvieglo programmatūras izstrādes procesa testēšanas fāzi. Papildus izstrādātajiem testu scenārijiem tika izveidota arī tehniskā dokumentācija.Aim of qualification thesis “Automatization of tests for functions of radio studio control system” is to develop automated tests for radio studio control system audio source profile settings. The result of this work has lead to automatization of tests for a certain portion of radio studio control system, which simplifies the testing phase of new software development. Technical documentation has been written in addition to test scenario