Fission yeast Stn1 is crucial for semi-conservative replication at telomeres and subtelomeres

The CST complex is a phylogenetically conserved protein complex consisting of CTC1/Cdc13, Stn1 and Ten1 that protects telomeres on linear chromosomes. Deletion of the fission yeast homologs stn1 and ten1 results in complete telomere loss; however, the precise function of Stn1 is still largely unknown. Here, we have isolated a high-temperature sensitive stn1 allele (termed stn1-1). stn1-1 cells abruptly lost telomeric sequence almost completely at the restrictive temperature. The loss of chromosomal DNA happened without gradual telomere shortening, and extended to 30 kb from the ends of chromosomes. We found transient and modest single-stranded G-strand exposure, but did not find any evidence of checkpoint activation in stn1-1 at the restrictive temperature. When we probed neutral-neutral 2D gels for subtelomere regions, we found no Y-arc-shaped replication intermediates in cycling cells. We conclude that the loss of telomere and subtelomere DNAs in stn1-1 cells at the restrictive temperature is caused by very frequent replication fork collapses specifically in subtelomere regions. Furthermore, we identified two independent suppressor mutants of the high-temperature sensitivity of stn1-1: a multi-copy form of pmt3 and a deletion of rif1. Collectively, we propose that fission yeast Stn1 primarily safeguards the semi-conservative DNA replication at telomeres and subtelomeres

A comparison of training time for teaching optometric technicians how to perform Goldmann Applanation Tonometry and Keeler Pulsair 3000

Goldmann Applanation Tonometry (GAT) has long been considered the Gold Standard method of measuring intraocular pressure. However, it may be somewhat complex and lengthy for a doctor to teach his staff members. It is proposed in this thesis project that it would be less time-consuming to train naive subjects to adequately perform tonometry using the Keeler Pulsair 3000 (KP3) versus Goldmann Applanation Tonometry. Ten subjects were timed on the length of time it took to learn each apparatus. Each subject was then asked to complete a questionnaire at the end of the lesson. The results showed that the KP3 required half the amount of time to learn than the GAT. Subject response to the questionnaire was in favor of the KP3. Because the Keeler Pulsair 3000 requires less training time and is easier to perform, it may serve as a good screening tool for optometrists in their practices

Um modelo Weibull bivariado para riscos competitivos

Orientador : Cicilia Yuko WadaTese (doutorado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação CientificaResumo: Neste trabalho foram investigados alguns models de riscos competitivos com duas causas de falhas baseados em modelos bivariados. Nesta situação, as variáveis aleatórias tempos de falhas TI e T2 estão associados com as causas C1 e C2 respectivamente. O tempo de falha observado é T = min(T1, T2) correspondendo a causa de falha C1 ou C2. Esta abordagem parece ser a mais adequada do ponto de vista estatístico, no entanto, possui o problema de identificabilidade na maioria das distribuições bivariadas. O modelo Weibull bivariado de Ryu (1993), que é absolutamente contínuo, foi estudado e a partir deste, desenvolvido um modelo de riscos competitivos. O principal objetivo deste trabalho foi a procura de um modelo bivariado absolutamente contínuo tal que o modelo de riscos competitivos tenha as suas distribuições marginais identificadas. O modelo bivariado de Ryu foi modificado de tal forma que as funções risco "net" e "crude" sejam iguais. Esta é uma condição necessária para a identificabilidade de suas distribuições marginais (Fleming e Harrington, 1991). A estimação dos parâmetros do modelo através do estimador de máxima verossimilhança foi estudada. Foi desenvolvido o modelo com covariáveis e estudados testes de algumas hipóteses de interesse. Foram realizados estudos de simulação para a comparação dos modelos Weibulls bivariados propostos, de Ryu e independentes e também os de riscos competitivos proposto e independentes. Aplicações de dados reais bivariados e de riscos competitivos são apresentadosAbstract: In this research it was investigated some competing risks models with two causes of failure based in bivariate models. In this situation, the random variables failure times TI and T2 are associated with causes CI and C2 respectively, so that, the observed time is T = min(TI, T2) corresponding to the cause of failure Ci, i = 1, 2. Although this approach appears to be more adequated at the statistical point ofview, the identifiability problems arises in the most ofbivariate distribution. The bivariate Weibull model of Ryu (1993), which is absolutely continuous, it was studied and developed a competing risks models based in this bivariate model. The main goal of this job was the search of a absolutely continuous bivariate model in order to obtain a competing risks model with marginaIs identifiable. The Ryu's bivariate model was modified in order to derive a Weibull competing risks model with crude and net hazards equals. This condition allow identifiability of the marginaIs corresponding to each cause of failure (Fleming and Harrington, 1991). Identifiability and estimation of its parameters by maximum likelihood method were investigated. Also, it was developed the models considering the inclusion of covariate and tests some hypotheses of the interest were studied. Simulation studies for comparison of the proposed, Ryu's and independent bivariate weibull models and ofproposed and independent competing risks models were performed. Applications to real data also were presented.DoutoradoDoutor em Matemática Aplicad

Testes de hipoteses com alternativas restritas em modelos de riscos proporcionais

Orientador: Cicilia Yuko WadaDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação CientíficaResumo: Não informado.Abstract: Not informed.MestradoMestre em Estatístic

Tankyrase inhibition sensitizes cells to CDK4 blockade

Tankyrase (TNKS) 1/2 are positive regulators of WNT signaling by controlling the activity of the ss-catenin destruction complex. TNKS inhibitors provide an opportunity to suppress hyperactive WNT signaling in tumors, however, they have shown limited anti-proliferative activity as a monotherapy in human cancer cell lines. Here we perform a kinome-focused CRISPR screen to identify potential effective drug combinations with TNKS inhibition. We show that the loss of CDK4, but not CDK6, synergizes with TNKS1/2 blockade to drive G1 cell cycle arrest and senescence. Through precise modelling of cancer-associated mutations using cytidine base editors, we show that this therapeutic approach is absolutely dependent on suppression of canonical WNT signaling by TNKS inhibitors and is effective in cells from multiple epithelial cancer types. Together, our results suggest that combined WNT and CDK4 inhibition might provide a potential therapeutic strategy for difficult-to-treat epithelial tumors

Silício na eficiência de Azospirillum brasilense em trigo

O trabalho teve como objetivo avaliar a ação do silício durante o desenvolvimento inicial de plantas de trigo inoculadas com Azospirillum brasilense. A pesquisa compreendeu o ano agrícola 2015, testando dois corretivos agrícolas (calcário dolomítico e silicato de cálcio e magnésio), quatro métodos de inoculação (ausente, sulco, sulco/foliar e foliar) da estirpe Ab-V5 de Azospirillum brasilense e um controle, compondo fatorial 4x2+1 em delineamento inteiramente casualizado com quatro repetições. Foram avaliados índice de velocidade de emergência (IVE), altura de plantas (cm), volume de raiz (mL), número de perfilhos e folhas por planta (n° planta?1), e quantidade de nitrogênio e silício de parte aérea e raiz (g kg-1). A inoculação em sulco e foliar promove o acumulo de nitrogênio na parte aérea, mas reduz o número de perfilhos, que se reproduz sobre a menor produção de matéria seca desta região. O silício incrementa a altura de plantas de trigo, melhora a eficiência de absorção de nitrogênio na parte aérea e não restringe a atividade do Azospirillum brasilense, independente do método de inoculação, podendo ser empregado como insumo adicional à cultura

KAT7 is a genetic vulnerability of acute myeloid leukemias driven by MLL rearrangements.

Histone acetyltransferases (HATs) catalyze the transfer of an acetyl group from acetyl-CoA to lysine residues of histones and play a central role in transcriptional regulation in diverse biological processes. Dysregulation of HAT activity can lead to human diseases including developmental disorders and cancer. Through genome-wide CRISPR-Cas9 screens, we identified several HATs of the MYST family as fitness genes for acute myeloid leukemia (AML). Here we investigate the essentiality of lysine acetyltransferase KAT7 in AMLs driven by the MLL-X gene fusions. We found that KAT7 loss leads to a rapid and complete loss of both H3K14ac and H4K12ac marks, in association with reduced proliferation, increased apoptosis, and differentiation of AML cells. Acetyltransferase activity of KAT7 is essential for the proliferation of these cells. Mechanistically, our data propose that acetylated histones provide a platform for the recruitment of MLL-fusion-associated adaptor proteins such as BRD4 and AF4 to gene promoters. Upon KAT7 loss, these factors together with RNA polymerase II rapidly dissociate from several MLL-fusion target genes that are essential for AML cell proliferation, including MEIS1, PBX3, and SENP6. Our findings reveal that KAT7 is a plausible therapeutic target for this poor prognosis AML subtype