Andrea Eberle

SMG6 promotes endonucleolytic cleavage of nonsense mRNA in human cells

From yeast to humans, mRNAs harboring premature termination codons (PTCs) are recognized and degraded by nonsense-mediated mRNA decay (NMD). However, degradation mechanisms of NMD have been suggested to differ between species. In Drosophila melanogaster, NMD is initiated by endonucleolysis near the PTC, whereas in yeast and human cells the current view posits that NMD occurs by exonucleolysis from one or both RNA termini. Here we report that degradation of human nonsense mRNAs can be initiated by PTC-proximal endonucleolytic cleavage. We identify the metazoan-specific NMD factor SMG6 as the responsible endonuclease by demonstrating that mutation of conserved residues in its nuclease domain—the C-terminal PIN motif—abolishes endonucleolysis in vivo and in vitro. Our data lead to a revised mechanistic model for degradation of nonsense mRNA in human cells and suggest that endonucleolytic cleavage is a conserved feature in metazoan NMD.

Posttranscriptional Gene Regulation by Spatial Rearrangement of the 3′ Untranslated Region

Translation termination at premature termination codons (PTCs) triggers degradation of the aberrant mRNA, but the mechanism by which a termination event is defined as premature is still unclear. Here we show that the physical distance between the termination codon and the poly(A)-binding protein PABPC1 is a crucial determinant for PTC recognition in human cells. “Normal” termination codons can trigger nonsense-mediated mRNA decay (NMD) when this distance is extended; and vice versa, NMD can be suppressed by folding the poly(A) tail into proximity of a PTC or by tethering of PABPC1 nearby a PTC, indicating an evolutionarily conserved function of PABPC1 in promoting correct translation termination and antagonizing activation of NMD. Most importantly, our results demonstrate that spatial rearrangements of the 3′ untranslated region can modulate the NMD pathway and thereby provide a novel mechanism for posttranscriptional gene regulation.

Fear of recurrence in long-term breast cancer survivors - Still an issue. Results on prevalence, determinants, and the association with quality of life and depression from the Cancer Survivorship - A multi-regional population-based study

Fear of recurrence (FoR) is a widespread problem among breast cancer survivors. So far, little is known about prevalence, determinants, and consequences of FoR specifically in long‐term breast cancer survivors, even though it was found to be one of the most important concerns in this group.

Sex Differences in Colorectal Cancer Survival: Population-Based Analysis of 164,996 Colorectal Cancer Patients in Germany

Risk of colorectal cancer (CRC) is considerably higher in men compared to women; however, there is inconclusive evidence of sex differences in CRC prognosis. We aimed to assess and explain sex differences in 5-year relative survival using standard and model-based period analysis among 164,996 patients diagnosed with CRC from 1997 to 2006 and reported to 11 German cancer registries covering a population of 33 million inhabitants. Age-adjusted 5-year relative survival was higher in women (64.5% vs. 61.9%, P<0.0001). A substantial survival advantage of women was confirmed in multivariate analysis after adjusting for CRC stage and subsite in subjects under 65 years of age (relative excess risk, RER 0.86, 95% CI 0.82–0.90), but not in older subjects (RER 1.01, 95% CI 0.98–1.04); this pattern was similar in the 1st and in the 2nd to 5th year after diagnosis. The survival advantage of women varied by CRC stage and age and was most pronounced for localized disease (RERs 0.59–0.88 in various age subgroups) and in patients under 45 years of age (RERs 0.59, 0.72 and 0.76 in patients with localized, regional or advanced disease, respectively). On the contrary, sex differences in survival did not vary by location of CRC. In conclusion, our large population-based study confirmed a survival advantage of female compared to male CRC patients, most notably in young and middle aged patients and patients with localized disease. The effect of sex hormones, either endogenous or through hormonal replacement therapy, might be the most plausible explanation for the observed patterns.

Socioeconomic deprivation and cancer survival in Germany: An ecological analysis in 200 districts in Germany

Although socioeconomic inequalities in cancer survival have been demonstrated both within and between countries, evidence on the variation of the inequalities over time past diagnosis is sparse. Furthermore, no comprehensive analysis of socioeconomic differences in cancer survival in Germany has been conducted. Therefore, we analyzed variations in cancer survival for patients diagnosed with one of the 25 most common cancer sites in 1997–2006 in ten population‐based cancer registries in Germany (covering 32 million inhabitants). Patients were assigned a socioeconomic status according to the district of residence at diagnosis. Period analysis was used to derive 3‐month, 5‐year and conditional 1‐year and 5‐year age‐standardized relative survival for 2002–2006 for each deprivation quintile in Germany. Relative survival of patients living in the most deprived district was compared to survival of patients living in all other districts by model‐based period analysis. For 21 of 25 cancer sites, 5‐year relative survival was lower in the most deprived districts than in all other districts combined. The median relative excess risk of death over the 25 cancer sites decreased from 1.24 in the first 3 months to 1.16 in the following 9 months to 1.08 in the following 4 years. Inequalities persisted after adjustment for stage. These major regional socioeconomic inequalities indicate a potential for improving cancer care and survival in Germany. Studies on individual‐level patient data with access to treatment information should be conducted to examine the reasons for these socioeconomic inequalities in cancer survival in more detail.

Recent cancer survival in Germany: an analysis of common and less common cancers.

The monitoring of cancer survival by population‐based cancer registries is a prerequisite to evaluate the current quality of cancer care. Our study provides 1‐, 5‐ and 10‐year relative survival as well as 5‐year relative survival conditional on 1‐year survival estimates and recent survival trends for Germany using data from 11 population‐based cancer registries, covering around one‐third of the German population. Period analysis was used to estimate relative survival for 24 common and 11 less common cancer sites for the period 2007–2010. The German and the United States survival estimates were compared using the Surveillance, Epidemiology and End Results 13 database. Trends in cancer survival in Germany between 2002–2004 and 2008–2010 were described. Five‐year relative survival increased in Germany from 2002–2004 to 2008–2010 for most cancer sites. Among the 24 most common cancers, largest improvements were seen for multiple myeloma (8.0% units), non‐Hodgkin lymphoma (6.2% units), prostate cancer (5.2% units) and colorectal cancer (4.6% units). In 2007–2010, the survival disadvantage in Germany compared to the United States was largest for cancers of the mouth/pharynx (−11.0% units), thyroid (−6.8% units) and prostate (−7.5% units). Although survival estimates were much lower for elderly patients in both countries, differences in age patterns were observed for some cancer sites. The reported improvements in cancer survival might reflect advances in the quality of cancer care on the population level as well as increased use of screening in Germany. The survival differences across countries and the survival disadvantage in the elderly require further investigation.

Survival of adults with acute lymphoblastic leukemia in Germany and the United States.

Background Adulthood acute lymphoblastic leukemia (ALL) is a rare disease. In contrast to childhood ALL, survival for adults with ALL is poor. Recently, new protocols, including use of pediatric protocols in young adults, have improved survival in clinical trials. Here, we examine population level survival in Germany and the United States (US) to gain insight into the extent to which changes in clinical trials have translated into better survival on the population level. Methods Data were extracted from the Surveillance, Epidemiology, and End Results database in the US and 11 cancer registries in Germany. Patients age 15–69 diagnosed with ALL were included. Period analysis was used to estimate 5-year relative survival (RS). Results Overall 5-year RS was estimated at 43.4% for Germany and 35.5% for the US (p = 0.004), with a decrease in survival with increasing age. Survival was higher in Germany than the US for men (43.6% versus 37.7%, p = 0.002) but not for women (42.4% versus 40.3%, p>0.1). Five-year RS estimates increased in Germany and the US between 2002 and 2006 by 11.8 and 7.3 percent units, respectively (p = 0.02 and 0.04, respectively). Conclusions Survival for adults with ALL continues to be low compared with that for children, but a substantial increase in 5-year survival estimates was seen from 2002 to 2006 in both Germany and the US. The reasons for the survival differences between both countries require clarification.

Eukaryotic initiation factor 4G suppresses nonsense-mediated mRNA decay by two genetically separable mechanisms.

Nonsense-mediated mRNA decay (NMD), which is best known for degrading mRNAs with premature termination codons (PTCs), is thought to be triggered by aberrant translation termination at stop codons located in an environment of the mRNP that is devoid of signals necessary for proper termination. In mammals, the cytoplasmic poly(A)-binding protein 1 (PABPC1) has been reported to promote correct termination and therewith antagonize NMD by interacting with the eukaryotic release factors 1 (eRF1) and 3 (eRF3). Using tethering assays in which proteins of interest are recruited as MS2 fusions to a NMD reporter transcript, we show that the three N-terminal RNA recognition motifs (RRMs) of PABPC1 are sufficient to antagonize NMD, while the eRF3-interacting C-terminal domain is dispensable. The RRM1-3 portion of PABPC1 interacts with eukaryotic initiation factor 4G (eIF4G) and tethering of eIF4G to the NMD reporter also suppresses NMD. We identified the interactions of the eIF4G N-terminus with PABPC1 and the eIF4G core domain with eIF3 as two genetically separable features that independently enable tethered eIF4G to inhibit NMD. Collectively, our results reveal a function of PABPC1, eIF4G and eIF3 in translation termination and NMD suppression, and they provide additional evidence for a tight coupling between translation termination and initiation.

Survival among adolescents and young adults with cancer in Germany and the United States: An international comparison

Serious concern arose in the scientific literature about the state of and progress in cancer survival among adolescent and young adult (AYA) patients in the recent years. We provide an up‐to‐date international comparison of survival among AYA patients. Using population‐based cancer data from 11 German cancer registries and the SEER Program of the United States (covering populations of 39 and 33 million people, respectively), standardized tumor group classifications, period analysis and modeling, we compared the 5‐year relative survival of AYA patients in the age groups 15–29 and 30–39 to survival seen among adults aged 40–49 for the 2002–2006 period. Additionally, we also provide an age‐specific survival comparison between the two countries. In 2002–2006, for the overwhelming majority of the more than 30 types of cancer examined, AYA patients aged both 15–29 and 30–39 years had higher or similar survival than patients in the age group 40–49 in both countries. A numerically large and statistically significant survival deficit among AYA patients was only found for breast carcinomas in both populations, and colorectal and stomach carcinoma in the United States for the age group 15–29. Overall, results of the country‐specific comparisons did not indicate systematic differences. With very few exceptions, no survival deficit between AYA patients and adults aged 40–49 years was found in either of the examined countries in the first decade of the 21st century.

Equal transcription rates of productively and nonproductively rearranged immunoglobulin mu heavy chain alleles in a pro-B cell line.

During B cell maturation, immunoglobulin (Ig) genes frequently acquire premature translation-termination codons (PTCs) as a result of the somatic rearrangement of V, D, and J gene segments. However, it is essential for a B lymphocyte to produce only one kind of antibody and therefore to ensure that the heavy and light chain polypeptides are expressed exclusively from the corresponding functional alleles, whereas no protein is made from the nonproductively rearranged alleles. At the post-transcriptional level, a well-studied mRNA quality control mechanism, termed nonsense-mediated mRNA decay (NMD), recognizes and degrades PTC-containing mRNAs in a translation-dependent manner. In addition, transcriptional silencing of PTC-containing Ig-mu and Ig-gamma heavy chain reporter genes was observed in HeLa cells. To investigate the silencing of nonproductively rearranged Ig genes in a more physiological context, we analyzed a monoclonal line of immortalized murine pro-B cells harboring one productively (PTC-) and one nonproductively (PTC+) rearranged Ig-mu heavy chain allele. We show that the steady-state abundance of PTC+ mRNA was approximately 40-fold lower when compared to that of the PTC- mRNA. However, both the PTC+ and PTC- allele seemed to be equally well transcribed since the abundances of PTC+ and PTC- pre-mRNA were very similar and chromatin immunoprecipitations revealed comparable occupancy of RNA polymerase II and acetylated histone H3 on both alleles. Altogether, we found no evidence for transcriptional silencing of the PTC+ allele in this pro-B cell line; hence, the efficient down-regulation of the PTC+ Ig-mu mRNA results entirely from NMD.