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Proteomic analyses revealed that a group of interferon-stimulated genes suppresses LINE-1 retrotransposon activities, including HELZ2, which reduces LINE-1 RNA and the associated innate immune response levels.

Genomic rearrangements (gross chromosomal rearrangements, GCRs) threatens genome integrity and cause cell death or tumor formation. At the terminus of linear chromosomes, a telomere-binding protein complex, called shelterin, ensures chromosome stability by preventing chromosome end-to-end fusions and regulating telomere length homeostasis. As such, shelterin-mediated telomere functions play a pivotal role in suppressing GCR formation. However, it remains unclear whether the shelterin proteins play any direct role in inhibiting GCR at non-telomeric regions. Here, we have established a GCR assay for the first time in fission yeast and measured GCR rates in various mutants. We found that fission yeast cells lacking shelterin components Taz1 or Rap1 (mammalian TRF1/2 or RAP1 homologues, respectively) showed higher GCR rates compared to wild-type, accumulating large chromosome deletions. Genetic dissection of Rap1 revealed that Rap1 contributes to inhibiting GCRs via two independent pathways. The N-terminal BRCT-domain promotes faithful DSB repair, as determined by I-SceI-mediated DSB-induction experiments; moreover, association with Poz1 mediated by the central Poz1-binding domain regulates telomerase accessibility to DSBs, leading to suppression of de novo telomere additions. Our data highlight unappreciated functions of the shelterin components Taz1 and Rap1 in maintaining genome stability, specifically by preventing non-telomeric GCRs.

Summary: The molecular mechanism of memory formation remains a mystery. Here, we show that TERT, the catalytic subunit of telomerase, gene knockout (Tert−/−) causes extremely poor ability in spatial memory formation. Knockdown of TERT in the dentate gyrus of adult hippocampus impairs spatial memory processes, while overexpression facilitates it. We find that TERT plays a critical role in neural development including dendritic development and neuritogenesis of hippocampal newborn neurons. A monosynaptic pseudotyped rabies virus retrograde tracing method shows that TERT is required for neural circuit integration of hippocampal newborn neurons. Interestingly, TERT regulated neural development and spatial memory formation in a reverse transcription activity-independent manner. Using X-ray irradiation, we find that hippocampal newborn neurons mediate the modulation of spatial memory processes by TERT. These observations reveal an important function of TERT through a non-canonical pathway and encourage the development of a TERT-based strategy to treat neurological disease-associated memory impairment. : In this article, Qi-Gang Zhou and colleagues show that spatial memory formation, neural development including dendritic development and neuritogenesis, and neural circuit integration are impaired in Tert gene knockout mice. Hippocampal TERT accounts for these phenotypes in a reverse transcription activity-independent manner. Keywords: telomerase, neural progenitor cells, hippocampus, neural development, circuit integration

Telomeric and subtelomeric regions of human chromosomes largely consist of highly repetitive and redundant DNA sequences, resulting in a paucity of unique DNA sequences specific to individual telomeres. Accordingly, it is difficult to analyze telomere metabolism on a single-telomere basis. To circumvent this problem, we have exploited a human artificial chromosome (HAC#21) derived from human chromosome 21 (hChr21). HAC#21 was generated through truncation of the long arm of native hChr21 by the targeted telomere seeding technique. The newly established telomere of HAC#21 lacks canonical subtelomere structures but possesses unique sequences derived from the target vector backbone and the internal region of hChr21 used for telomere targeting, which enabled us to molecularly characterize the single HAC telomere. We established HeLa and NIH-3T3 sub-lines containing a single copy of HAC#21, where it was robustly maintained. The seeded telomere is associated with telomeric proteins over a length similar to that reported in native telomeres, and is faithfully replicated in mid-S phase in HeLa cells. We found that the seeded telomere on HAC#21 is transcribed from the newly juxtaposed site. The transcript, HAC-telRNA, shares several features with TERRA (telomeric repeat-containing RNA): it is a short-lived RNA polymerase II transcript, rarely contains a poly(A) tail, and associates with chromatin. Interestingly, HAC-telRNA undergoes splicing. These results suggest that transcription into TERRA is locally influenced by the subtelomeric context. Taken together, we have established human and mouse cell lines that will be useful for analyzing the behavior of a uniquely identifiable, functional telomere.

Induced pluripotent stem cell (iPSC) technology can be used to model human disorders, create cell-based models of human diseases, including neurodegenerative diseases, and in establishing therapeutic strategies. To detect subtle cellular abnormalities associated with common late-onset disease in iPSCs, valid control iPSCs derived from healthy donors free of serious late-onset diseases are necessary. Here, we report the generation of iPSCs from fibroblasts obtained immediately postmortem from centenarian donors (106- and 109-years-old) who were extremely healthy until an advanced age. The iPSCs were generated using a conventional method involving OCT4, SOX2, KLF4, and c-MYC, and then differentiated into neuronal cells using a neurosphere method. The expression of molecules that play critical roles in late-onset neurodegenerative diseases by neurons differentiated from the centenarian-iPSCs was compared to that of neurons differentiated from iPSCs derived from familial Alzheimer's disease and familial Parkinson's disease (PARK4: triplication of the α synuclein gene) patients. The results indicated that our series of iPSCs would be useful in neurodegeneration research. The iPSCs we describe, which were derived from donors with exceptional longevity who were presumed to have no serious disease risk factors, would be useful in longevity research and as valid super-controls for use in studies of various late-onset diseases.