Mnk kinase pathway: Cellular functions and biological outcomes

The mitogen-activated protein kinase(MAPK) interacting protein kinases 1 and 2(Mnk1 and Mnk2) play important roles in controlling signals involved in mRNA translation. In addition to the MAPKs(p38 or Erk), multiple studies suggest that the Mnk kinases can be regulated by other known kinases such as Pak2 and/or other unidentified kinases by phosphorylation of residues distinct from the sites phosphorylated by the MAPKs. Several studies have established multiple Mnk protein targets, including PSF, heterogenous nuclear ribonucleoprotein A1, Sprouty 2 and have lead to the identification of distinct biological functions and substrate specificity for the Mnk kinases. In this review we discuss the pathways regulating the Mnk kinases, their known substrates as well as the functional consequences of engagement of pathways controlled by Mnk kinases. These kinases play an important role in mRNA translation via their regulation of eukaryotic initiation factor 4E(eIF4E) and their functions have important implications in tumor biology as well as the regulation of drug resistance to anti-oncogenic therapies. Other studies have identified a role for the Mnk kinases in cap-independent mRNA translation, suggesting that the Mnk kinases can exert important functional effects independently of the phosphorylation of eIF4 E. The role of Mnk kinases in inflammation and inflammationinduced malignancies is also discussed.

Cancer metabolic reprogramming: importance, main features, and potentials for precise targeted anti-cancer therapies

Cancer cells are well documented to rewire their metabolism and energy production networks to support and enable rapid proliferation, continuous growth, survival in harsh conditions, invasion, metastasis, and resistance to cancer treatments. Since Dr. Otto Warhurg＇s discovery about altered cancer cell metabolism in 1930, thousands of studies have shed light on various aspects of cancer metabolism with a common goal to find new ways for effectively eliminating tumor cells by targeting their energy metabolism. This review highlights the importance of the main features of cancer metabolism, summarizes recent remarkable advances in this field, and points out the potentials to translate these scientific findings into life-saving diagnosis and therapies to help cancer patients.

Nonmetabolic functions of pyruvate kinase isoform M2 in controlling cell cycle progression and tumorigenesis

Pyruvate kinase catalyzes the rate-limiting final step of glycolysis, generating adenosine triphosphate (ATP) and pyruvate. The M2 tumor-specific isoform of pyruvate kinase (PKM2) promotes glucose uptake and lactate production in the presence of oxygen, known as aerobic glycolysis or the Warburg effect. As recently reported in Nature, PKM2, besides its metabolic function, has a nonmetabolic function in the direct control of cell cycle progression by activating β-catenin and inducing expression of the β-catenin downstream gene CCND1 (encoding for cyclin D1). This nonmetabolic function of PKM2 is essential for epidermal growth factor receptor (EGFR) activation-induced tumorigenesis.

Regulation of tumor cell migration by protein tyrosine phosphatase (PTP)-proline-, glutamate-, serine-,and threonine-rich sequence(PEST)

Protein tyrosine phosphatase (PTP)-proline-,glutamate-,serine-,and threonine-rich sequence (PEST) is ubiquitously expressed and is a critical regulator of cell adhesion and migration.PTP-PEST activity can be regulated transcriptionally via gene deletion or mutation in several types of human cancers or via post-translational modifications,including phosphorylation,oxidation,and caspase-dependent cleavage.PTP-PEST interacts with and dephosphorylates cytoskeletal and focal adhesion-associated proteins.Dephos-phorylation of PTP-PEST substrates regulates their enzymatic activities and/or their interaction with other proteins and plays an essential role in the tumor cell migration process.

Fluoxetine induces cytotoxic endoplasmic reticulum stress and autophagy in triple negative breast cancer

AIM: To investigate the mechanism of action of lipophilic antidepressant fluoxetine(FLX) in representative molecular subtypes of breast cancer.METHODS: The anti-proliferative effects and mechanistic action of FLX in triple-negative(SUM149PT) and luminal(T47D and Au565) cancer cells and nontransformed MCF10 A were investigated. Reverse phase protein microarray(RPPM) was performed with and without 10 μmol/L FLX for 24 and 48 h to determine which proteins are significantly changed. Viability and cell cycle analysis were also performed to determine drug effects on cell growth. Western blotting was used to confirm the change in protein expression examined by RPPM or pursue other signaling proteins. RESULTS: The FLX-induced cell growth inhibition in all cell lines was concentration- and time-dependent but less pronounced in early passage MCF10 A. In comparison to the other lines,cell growth reduction in SUM149 PT coincided with significant induction of endoplasmic reticulum(ER) stress and autophagy after 24 and 48 h of 10 μmol/L FLX,resulting in decreased translation of proteins along the receptor tyrosine kinase/Akt/mammalian target of rapamycin pathways. The increase in autophagy marker,cleaved microtubule-associated protein 1 light chain 3,in SUM149 PT after 24 h of FLX was likely due to increased metabolic demands of rapidly dividing cells and ER stress. Consequently,the unfolded protein response mediated by double-stranded RNA-dependent protein kinase-like ER kinase resulted in inhibition of protein synthesis,growth arrest at the G1 phase,autophagy,and caspase-7-mediated cell death.CONCLUSION: Our study suggests a new role for FLX as an inducer of ER stress and autophagy,resulting in death of aggressive triple negative breast cancer SUM149 PT.

Molecular Insights on the Transition of Non-invasive DCIS to Invasive Ductal Carcinoma

More than 90% of breast cancer-related deaths are caused by metastasis not primary tumor. To effectively reduce cancer mortality, it is extremely important to predict the risk of, and to intervene in, the critical transition from

Burden of nonalcoholic fatty liver disease and advanced fibrosis in a Texas Hispanic community cohort

AIM: To investigate the potential burden of nonalcoholic steatohepatitis(NASH) and advanced fibrosis in a hispanic community.METHODS: Four hundred and forty two participants with available ultrasonography data from the Cameron County Hispanic Cohort were included in this study. Each participant completed a comprehensive questionnaire regarding basic demographic information, medical history, medication use, and social and family history including alcohol use. Values of the nonalcoholic fatty liver disease fibrosis score(NFS), FIB4 index, BARD score, and Aspartate aminotransferase to Platelet Ratio Index(APRI) were computed using the blood samples collected within 6 mo of liver ultrasonography from each participant. Hepatic steatosis was determined by ultrasonography. As part of univariable analysis, for continuous variables, comparisons among groups were performed with student-t test, one way analysis of variance, and Mann-Whitney test. Pearson χ2 and the Fisher exact test are used to assess differences in categorical variables. For multivariable analyses, logistic regression analyses were performed to identify characteristics associated with hepatic steatosis. All reported P values are based two-sided tests, and a P value of less than 0.05 was considered to indicate statistical significance.RESULTS: The mean age and body mass index(BMI) of the study participants were 49.1 years and 31.3 kg/m2, respectively. Among them, 65.6% were females, 52% had hepatic steatosis, 49.5% had metabolic syndrome, and 29% had elevated aminotransferases. Based on established cut-offs for diagnostic panels, between 17%-63% of the entire cohort was predicted to have NASH with indeterminate or advanced fibrosis. Participants with hepatic steatosis had significantly higher BMI(32.9 ± 5.6 kg/m2 vs 29.6 ± 6.1 kg/m2, P < 0.001) and higher prevalence rates of elevation of ALT(42.2% vs 14.6%, P < 0.001), elevation of aspartate aminotransferase(38.7% vs 18.9%, P < 0.001), and metabolic syndrome(64.8% vs 33%, P < 0.001) than those without hepatic steatosis. The NFS scores(P = 0.002) and the APRI scores(P = 0.002) were significantly higher in those with steatosis but the scores of the FIB4 index and BARD were similar between the two groups. After adjusting for age, gender and BMI, elevated transaminases, metabolic syndrome and its components, intermediate NFS and APRI scores were associated hepatic steatosis in multivariable analysis. CONCLUSION: The burden of NASH and advanced fibrosis in the Hispanic community in South Texas may be more substantial than predicted from referral clinic studies.

不同辐射抗拒鼻咽癌细胞微小RNA差异表达的研究

目的:在验证鼻咽癌(nasopharygycarcinoma,NPC)细胞CNE-1和CNE-2不同辐射抗拒性的基础上,探索微小RNA(miRNA)在CNE-1和CNE-2中的表达差异。方法:通过观察X线照射对CNE-1和CNE-2细胞克隆形成数目的影响,利用SigmaPlot软件进行分析及线性二次模型拟合存活曲线,比较CNE-1和CNE-2细胞剂量存活曲线及其生物学参数;采用Paraflo microfluidic microRNA芯片检测,用激光扫描器收集杂交的图像,经LOWESS滤器规范信号后分析数据差异,根据Targetscan3·1数据库资料(http:∥www·targetscan·org),预测CNE-1和CNE-2细胞microRNA差异表达与NPC放射敏感性差异的关系。结果:发现在CNE-1和CNE-2细胞中miRNA的差异表达,即与CNE-2细胞比,在检测的326个microRNA中,CNE-1细胞中有20个miRNA上调,13个miRNA下调,其中检测量的绝对值在2000以上且两者相差在3倍以上的miRNA有hsa-miR-152、hsa-miR-7、hsa-miR-205和hsa-miR-572;分析结果提示明显差异表达的miRNA与放疗敏感性密切相关。结论:不同辐射抗拒NPC细胞株CNE-1和CNE-2细胞的microRNA的表达有差异;差异表达的miRNA与放疗敏感有关。

相同遗传背景不同辐射抗拒鼻咽癌细胞miRNA差异表达的研究

目的:在验证相同遗传背景鼻咽癌(NPC)细胞CNE-2R和CNE-2不同辐射抗拒性的基础上,探索微小RNA(miRNA)在CNE-2R和CNE-2中的表达差异与肿瘤辐射抗拒的关系。方法:通过观察X线照射对CNE-2R和CNE-2细胞克隆形成数目的影响,利用SigmaPlot软件进行分析及线性二次模型拟合存活曲线,比较CNE-2R和CNE-2细胞剂量存活曲线及其生物学参数;采用μParafloTM微流体芯片检测,用激光扫描仪(GenePix4000B,Molecular Device)采集杂交图像,经LOWESS滤器规范信号后分析数据差异,根据Targetscan311数据库资料(http://www.targetscan.org),预测CNE-2R和CNE-2细胞miRNA差异表达与NPC不同辐射抗拒的关系。结果:发现在CNE-2R和CNE-2细胞中存在miRNA的差异表达,即与CNE-2细胞比,在检测到的719个miRNA中,CNE-2R细胞中有37个上调,29个下调,其中检测量的绝对值≥2000且两者相差≥2倍的miRNA共12个:hsa-miR-200b、hsa-miR-224、hsa-miR-26b、hsa-miR-125a-5p、hsa-miR-205、hsa-let-7e、hsa-let-7g、hsa-miR-19b、hsa-miR-24、hsa-miR-103、hsa-miR-106b和hsa-miR-93。分析结果表明显著差异表达的miRNA与辐射抗拒密切相关。结论:相同遗传背景不同辐射抗拒NPC细胞株CNE-2R和CNE-2细胞的miRNA表达存在差异;差异表达的miRNA与辐射抗拒相关。

Ad-14-3-3σ对不同辐射抗拒的鼻咽癌细胞微小RNA表达的影响

目的:在明确Ad-14-3-3σ对不同辐射抗拒鼻咽癌(nasopharygycarcinoma,NPC)细胞CNE-1和CNE-2治疗作用的基础上,检测Ad-14-3-3σ对CNE-1和CNE-2细胞中差异表达的微小RNA(microR-NA,miRNA)的影响,探索CNE-1和CNE-2细胞中miRNA差异表达与NPC放射敏感性差异的关系。方法:用Ad-14-3-3σ转染CNE-1和CNE-2细胞;采用Paraflo microfluidic microRNA芯片检测,用激光扫描器收集杂交的图像,经LOWESS滤器规范信号后分析数据差异,根据Targetscan3.1数据库资料(http://www.targetscan.org)探索Ad-14-3-3σ对CNE-1和CNE-2中的miRNA差异表达的影响,预测其差异表达与NPC放射敏感性差异的关系。结果:Ad-14-3-3σ处理细胞以后,CNE-1与CNE-2相比较,有37个microRNA有明显差异,CNE-1中有17个上调,20个下调。其中倍数变化在3倍以上且2者检测量数量差异达到1000以上的有6个:hsa-miR-152、hsa-miR-205、hsa-miR-203、hsa-miR-7、hsa-miR-636和hsa-miR-100。结论:Ad-14-3-3σ能够改变微小RNA(microRNA,miRNA)在CNE-1和CNE-2中的表达模式,缩小CNE-1和CNE-2之间miRNA的表达差异,而这些miRNA可能跟肿瘤的发生和放疗敏感性有关。

Therapeutic strategies for targeting the ovarian tumor stroma

Epithelial ovarian cancer is the most lethal type of gynecologic malignancy. Sixty percent of women who are diagnosed with ovarian cancer present with advancedstage disease that involves the peritoneal cavity and these patients have a 5-year survival rate of less than 30%. For more than two decades, tumor-debulking surgery followed by platinum-taxane combination chemotherapy has remained the conventional first-line treatment of ovarian cancer. Although the initial response rate is 70%-80%, most patients with advancedstage ovarian cancer eventually relapse and succumb to recurrent chemoresistant disease. A number of molecular aberrations that drive tumor progression have been identified in ovarian cancer cells and intensive efforts have focused on developing therapeutic agents that target these aberrations. However, increasing evidence indicates that reciprocal interactions between tumor cells and various types of stromal cells also play important roles in driving ovarian tumor progression and that these stromal cells represent attractive therapeutic targets. Unlike tumor cells, stromal cells within the tumor microenvironment are in general geneticallystable and are therefore less likely to become resistant to therapy. This concise review discusses the biological significance of the cross-talk between ovarian cancer cells and three major types of stromal cells(endothelial cells, fibroblasts, macrophages) and the development of new-generation therapies that target the ovarian tumor microenvironment.

A Novel mRNA Signature Related to Immunity to Predict Survival and Immunotherapy Response in Hepatocellular Carcinoma

Background and Aims:Hepatocellular carcinoma(HCC)is the most common primary liver cancer and the incidence and mortality rates are increasing.Given the limited treatments of HCC and promising application of immunotherapy for cancer,we aimed to identify an immune-related prognostic signature that can predict overall survival(OS)rates and immunotherapy response in HCC.Methods:The initial signature development was conducted using a training dataset from the Cancer Genome Atlas followed by independent internal and external validations from that resource and the Gene Expression Omnibus.A signature based nomogram was generated using multivariate Cox regression analysis.The associations of signature score with tumor immune phenotype and response to immunotherapy were analyzed using single-sample gene set enrichment analysis and tumor immune dysfunction and exclusion algorithm.A cohort from Zhongshan Hospital was employed to verify the pre dictive robustness of the signature regarding prognostic risk and immunotherapy response.Results:The prognostic signature,IGS_(HCC),consisting of 22 immune-related genes,had independent prognostic ability,with training and validation cohorts.Also,IGS_(HCC)stratified HCC patients with different outcomes in subgroups.The prognostic accuracy of IGS_(HCC)was better than three reported prognostic signatures.The IGS_(HCC)-based nomogram had high accuracy and significant clinical benefits in predicting 3-and 5-year OS.IGS_(HCC)reflected distinct immunosuppressive phenotypes in low-and high-score groups.Patients with low IGS_(HCC)scores were more likely than those with high scores to benefit from immunotherapy.Conclusions:IGS_(HCC)predicted HCC prognosis and response to immunotherapy,and contributed to individualized clinical management.

Measurement of Protein 53 Diffusion Coefficient in Live HeLa Cells Using Raster Image Correlation Spectroscopy (RICS)

We have applied Raster Image Correlation Spectroscopy (RICS) technique to characterize the dynamics of protein 53 (p53) in living cells before and after the treatment with DNA damaging agents. HeLa cells expressing Green Fluores-cent Protein (GFP) tagged p53 were incubated with and without DNA damaging agents, cisplatin or eptoposide, which are widely used as chemotherapeutic drugs. Then, the diffusion coefficient of GFP-p53 was determined by RICS and it was significantly reduced after the drug treatment while that of the one without drug treatment was not. It is suggested that the drugs induced the interaction of p53 with either other proteins or DNA. Together, our results demonstrated that RICS is able to detect the protein dynamics which may be associated with protein-protein or protein-DNA interactions in living cells and it may be useful for the drug screening.

糖尿病对促进乳腺癌生长的影响

背景与目的2型糖尿病(typeⅡdiabetes mellitus,DM2)是包括乳腺癌在内的多种癌症的危险因素。目前,尚未建立可用于研究的糖尿病乳腺癌小鼠模型。另外,调节癌症生长的糖尿病信号通路也尚未明确。在本研究中,我们建立了一个糖尿病乳腺癌小鼠模型,并证实了糖尿病在乳腺癌进展中的影响。方法通过将瘦素受体突变(Lepr^(db/+))小鼠和MMTV-ErbB2/neu小鼠杂交,成功构建了人表皮生长因子受体2阳性(human epidermal growth factor receptor 2,Her2^(+)或ERBB2)的乳腺癌转基因小鼠模型。用抗糖尿病药物治疗该小鼠模型来评价治疗DM2对肿瘤生长的影响。用磁共振波谱成像分析肿瘤代谢情况。结果用二甲双胍/罗格列酮治疗MMTV-ErbB2/Lepr^(db/db)小鼠模型可降低血清胰岛素水平,延长生存,降低肿瘤累积发生率,抑制肿瘤进展。超极化^(13)C标记的丙酮酸/乳酸转换代谢流降低,表明抗胰岛素抵抗治疗抑制了体内实验中肿瘤糖酵解。用二甲双胍处理MMTV-ErbB2/Lepr^(db/db)转基因小鼠来源的肿瘤细胞,降低了耗氧量和乳酸产量,使细胞代谢发生了重新编程。二甲双胍可降低Myc和丙酮酸激酶M2型同工酶(pyruvate kinase isozyme 2,PKM2)的表达,引起代谢重编程。另外,二甲双胍可阻断mTOR/AKT信号通路并改变脂肪因子谱。结论MMTV-ErbB2/Lepr^(db/db)转基因小鼠模型可用于糖尿病HER2^(+)人乳腺癌的研究。本研究明确了糖尿病状态下HER2^(+)人乳腺癌中失调的信号通路,该通路可被抗胰岛素抵抗治疗干预。

ZRANB1 is an NBS1 deubiquitinase and a potential target to overcome radioresistance and PARP inhibitor resistance in triple-negative breast cancer

Poly(ADP-ribose)polymerase inhibitors(PARPi)are used to treat ovarian cancer and triple-negative breast cancer(TNBC)with defective homologous recombination repair pathways.However,de novo and acquired PARPi resistance limits clinical benefits.1 The MRE11-RAD50-NBS1(MRN)complex mediates the sensing,processing,and signaling of DNA double-strand breaks(DSBs)and plays important roles in the efficacy of PARPi and radiation treatment,2 and yet the mechanisms for the regulation and degradation of the MRN complex are not well understood.ZRANB1,also known as Trabid,is a breast cancer-promoting deubiquitinase that preferentially cleaves K29-,K33-,and K63-linked ubiquitin chains,3 but its role in therapy resistance remains unknown.

Amino acid transporter SLC7A11/ xCT at the crossroads of regulating redox homeostasis and nutrient dependency of cancer

Cancer cells often upregulate nutrient transporters to fulfill their increased biosynthetic and bioenergetic needs,and to maintain redox homeostasis.One nutrient transporter frequently overexpressed in human cancers is the cystine/glutamate antiporter solute carrier family 7 member 11(SLC7A11;also known as xCT).SLC7A11 promotes cystine uptake and glutathione biosynthesis,resulting in protection from oxidative stress and ferroptotic cell death.Recent studies have unexpectedly revealed that SLC7A11 also plays critical roles in glutamine metabolism and regulates the glucose and glutamine dependency of cancer cells.This review discusses the roles of SLC7A11 in regulating the anti-oxidant response and nutrient dependency of cancer cells,explores our current understanding of SLC7A11 regulation in cancer metabolism,and highlights key open questions for future studies in this emerging research area.A deeper understanding of SLC7A11 in cancer metabolism may identify new therapeutic opportunities to target this important amino acid transporter for cancer treatment.

The role of T-cell immunoglobulin mucin-3 and its ligand galectin-9 in antitumor immunity and cancer immunotherapy

Cancer treatment in the past few years has been transformed by a new kind of therapy that targets the immune system instead of the cancer itself to reinvigorate antitumor immunity with astonishing results. However, primary and acquired resistance to this type of treatment, namely immune checkpoint blockade(ICB), continue to counter treatment efficacy. In many cases, resistance has been attributed to defective or chronically enhanced interferon signaling and/or upregulation of alternative immune checkpoints,including T-cell immunoglobulin mucin-3(Tim-3) and its ligand galactin-9(Gal-9). In this article, we briefly describe the current knowledge of common checkpoint resistance mechanisms, focusing on the Tim-3/Gal-9 pathway as an alternative checkpoint that holds great promise as another target for ICB.

C-type lectin receptor-induced NF-κB activation in innate immune and inflammatory responses

The C-type lectin receptors （CLRs） belong to a large family of proteins that contain a carbohydrate recognition domain （CRD） and calcium binding sites on their extracellular domains. Recent studies indicate that many CLRs, such as Dectin-1, Dectin-2 and Mincle, function as pattern recognition receptors （PRRs） recognizing carbohydrate ligands from infected microorganisms. Upon ligand binding, these CLRs induce multiple signal transduction cascades through their own immunoreceptor tyrosine-based activation motifs （ITAMs） or interacting with ITAM-containing adaptor proteins such as FcRy. Emerging evidence indicate that CLR-induced signaling cascades lead to the activation of nuclear factor kappaB （NF-KB） family of transcriptional factors through a Syk- and CARD9-dependent pathway（s）. The activation of NF-κB plays a critical role in the induction of innate immune and inflammatory responses following microbial infection and tissue damages. In this review, we will summarize the recent progress on the signal transduction pathways induced by CLRs. and how these CLRs activate NF-κB and contribute to innate immune and inflammatory responses.

A multivariate analysis of prognostic determinants for stages Ⅱ and Ⅲ colorectal cancer in 141 patients

Background Previous prognosis analyses of colorectal cancer （CRC） patients with stage Ⅱ and Ⅲ disease were done as separate categories. The purpose of this study was to analyze prognostic factors associated with survival in a group of patients who underwent radical resection of stages Ⅱ and Ⅲ CRC.Methods A retrospective review was performed for 141 consecutive stages Ⅱ and Ⅲ patients who had undergone radical resection of coloractal adenocarcinoma between May 2003 and November 2003. Univariate and multivariate analyses were performed to assess the effect of record variables on disease free survival and overall survival.Results The median follow-up time was 59 months, and the 3-and 5-year survival rates were 76% and 68%,respectively. Four factors were independently associated with a worse disease-free survival： diabetes （hazard ratio （HR） 2.338; 95% confidence interval （CI） 1.011-5.407）, expression of cyclooxygenase-2 （Cox-2） （HR 0.335; 95% CI 0.126-0.888）, expression of matrix metalloproteinases 2 （MMP-2） （FIR 0.233; 95% CI 0.101-0.541）, expression of vascular endothelial growth factor （VEGF） （HR 0.295; 95% CI 0.088-0.996）. Four factors were independently associated with a worse overall survival： lymph nodes metastasis （HR 1.67; 95% CI 1.29-2.14）, Cox-2 positive （HR 0.056; 95% CI 0.247-0.731）, MMP-2 positive （HR 0.398; 95% CI 0.190-0.836）, VEGF （HR 0.364; 95% CI 0.090-0.716）.Conclusions Diabetes, expression of Cox-2, MMP-2 and VEGF were independently associated with a worse diseasefree survival. Lymph nodes metastasis, expression of Cox-2, MMP-2 and high level of VEGF predicted a poor overall survival.

TFIIA transcriptional activity is controlled by a ＇cleave-and-run＇ Exportin-1/Taspase 1-switc

Transcription factor TFIIA is controlled by complex regulatory networks including proteolysis by the protease Taspase 1, though the full impact of cleavage remains elusive. Here, we demonstrate that in contrast to the general assumption, de novo produced TFIIA is rapidly confined to the cytoplasm via an evolutionary conserved nuclear export signal （NES, amino acids ^21VINDVRDIFL^30）, interacting with the nuclear export receptor Exportin-1/chromosomal region maintenance 1 （Crml）. Chemical export inhibition or genetic inactivation of the NES not only promotes TFIIA＇s nuclear localization but also affects its transcrip- tional activity. Notably, Taspase 1 processing promotes TFIIA＇s nuclear accumulation by NES masking, and modulates its tran- scriptional activity. Moreover, TFIIA complex formation with the TATA box binding protein （TBP） is cooperatively enhanced by inhibition of proteolysis and nuclear export, leading to an increase of the ceil cycle inhibitor p16INK, which is counteracted by pre- vention of TBP binding. We here identified a novel mechanism how proteolysis and nuclear transport cooperatively fine-tune tran- scriptional programs.