Homology-directed DNA repair is essential for genome maintenance through templated DNA synthesis. Alternative lengthening of telomeres (ALT) necessitates homology-directed DNA repair to maintain telomeres in about 10–15% of human cancers. How DNA damage induces assembly and execution of a DNA replication complex (break-induced replisome) at telomeres or elsewhere in the mammalian genome is poorly understood. Here we define break-induced telomere synthesis and demonstrate that it utilizes a specialized replisome, which underlies ALT telomere maintenance. DNA double-strand breaks enact nascent telomere synthesis by long-tract unidirectional replication. Proliferating cell nuclear antigen (PCNA) loading by replication factor C (RFC) acts as the initial sensor of telomere damage to establish predominance of DNA polymerase δ (Pol δ) through its POLD3 subunit. Break-induced telomere synthesis requires the RFC–PCNA–Pol δ axis, but is independent of other canonical replisome components, ATM and ATR, or the homologous recombination protein Rad51. Thus, the inception of telomere damage recognition by the break-induced replisome orchestrates homology-directed telomere maintenance.

Osteoarthritis (OA) is a progressive disease of the joints characterized by degradation of articular cartilage. Although disease initiation may be multi-factorial, the cartilage destruction appears to be a result of uncontrolled proteolytic extracellular matrix destruction. A major component of the cartilage extracellular matrix is aggrecan, a proteoglycan that imparts compressive resistance to the tissue. Aggrecanase-mediated aggrecan degradation is a significant event in early stage OA. The relative contribution of individual ADAMTS-4 and ADAMTS-5 proteinases to cartilage destruction during OA has not been resolved completely. This review reveals that both ADAMTS-4/ADAMTS-5 are responsible for aggrecan degradation in a human model of OA, and is expected to list down the rational strategies which are being focussed for therapeutic intervention in OA.

Ovarian cancer (OVCA) inevitably acquires resistance to platinum chemotherapy and PARP inhibitors (PARPi). We show that acquisition of PARPi-resistance is accompanied by increased ATR-CHK1 activity and sensitivity to ATR inhibition (ATRi). However, PARPi-resistant cells are remarkably more sensitive to ATRi when combined with PARPi (PARPi-ATRi). Sensitivity to PARPi-ATRi in diverse PARPi and platinum-resistant models, including BRCA1/2 reversion and CCNE1 -amplified models, correlate with synergistic increases in replication fork stalling, double-strand breaks, and apoptosis. Surprisingly, BRCA reversion mutations and an ability to form RAD51 foci are frequently not observed in models of acquired PARPi-resistance, suggesting the existence of alternative resistance mechanisms. However, regardless of the mechanisms of resistance, complete and durable therapeutic responses to PARPi-ATRi that significantly increase survival are observed in clinically relevant platinum and acquired PARPi-resistant patient-derived xenografts (PDXs) models. These findings indicate that PARPi-ATRi is a highly promising strategy for OVCAs that acquire resistance to PARPi and platinum.

A case-control study was conducted to estimate the association of cartilage oligomeric matrix protein (COMP) with knee osteoarthritis (OA) and to examine the potential utility of COMP as a diagnostic and prognostic biomarker in early knee OA. The COMP levels were estimated in the blood sera of 150 subjects belonging to study group (n ¼ 100) and control one (n ¼ 50). Patients with confirmed clinical isolated knee OA diagnosed through American College of Rheumatology criteria were included and were without any other cause of knee pain. ELISA was used to determine the levels of COMP, interleukin-1b (IL-1b) and tumor necrosis factor-a (TNF-a). The median (range) serum COMP levels were observed to be 1117.21 ng/ml (125.03-4209.75 ng/ml) in OA patients and 338.62 ng/ml (118-589 ng/ml) in control subjects with p < 0.001. The COMP levels of study group were negatively correlated (correlation factor À0.88) with disease duration and positively correlated with age, BMI, pain score and IL-1b with correlation factors 0.86, 0.63, 0.76, and 0.79, respectively with p < 0.001. Gender differentiation was found in study group with 52% higher COMP level in males as compared to that of females. There was no significant correlation of COMP levels with radiological grading, erythrocyte sedimentation rate (ESR), hemoglobin (Hb), and TNF-a. The serum COMP levels may be used as a diagnostic OA marker along with prognostic value in determining the patients at risk of rapidly progressing this debilitating joint disease. The serum COMP level remains significantly high in first 3 years of disease duration. #

In the spindle midzone, microtubules from opposite half-spindles form bundles between segregating chromosomes. Microtubule bundles can either push or restrict chromosome movement during anaphase in different cellular contexts, but how these activities are achieved remains poorly understood. Here, we use high-resolution live-cell imaging to analyze individual microtubule bundles, growing filaments, and chromosome movement in dividing human cells. Within bundles, filament overlap length marked by the cross-linking protein PRC1 decreases during anaphase as chromosome segregation slows. Filament ends within microtubule bundles appear capped despite dynamic PRC1 turnover and submicrometer proximity to growing microtubules. Chromosome segregation distance and rate are increased in two human cell lines when microtubule bundle assembly is prevented via PRC1 knockdown. Upon expressing a mutant PRC1 with reduced microtubule affinity, bundles assemble but chromosome hypersegregation is still observed. We propose that microtubule overlap length reduction, typically linked to pushing forces generated within filament bundles, is needed to properly restrict spindle elongation and position chromosomes within daughter cells.

DNA repair is essential to maintain genomic integrity and initiate genetic diversity. While gene conversion and classical nonhomologous end-joining are the most physiologically predominant forms of DNA repair mechanisms, emerging lines of evidence suggest the usage of several noncanonical homology-directed repair (HDR) pathways in both prokaryotes and eukaryotes in different contexts. Here we review how these alternative HDR pathways are executed, specifically focusing on the determinants that dictate competition between them and their relevance to cancers that display complex genomic rearrangements or maintain their telomeres by homology-directed DNA synthesis.

Continuous bupivacaine infusion through TPVB is as effective as through TEA for pain management in patients with unilateral fractured ribs and the outcome after two techniques is comparable.

Approximately 15% of cancers use homologous recombination for alternative lengthening of telomeres (ALT). How the initiating genomic lesions invoke homology-directed telomere synthesis remains enigmatic. Here, we show that distinct dependencies exist for telomere synthesis in response to replication stress or DNA double-strand breaks (DSBs). RAD52 deficiency reduced spontaneous telomeric DNA synthesis and replication stress-associated recombination in G2, concomitant with telomere shortening and damage. However, viability and proliferation remained unaffected, suggesting that alternative telomere recombination mechanisms compensate in the absence of RAD52. In agreement, RAD52 was dispensable for DSB-induced telomere synthesis. Moreover, a targeted CRISPR screen revealed that loss of the structure-specific endonuclease scaffold SLX4 reduced the proliferation of RAD52null ALT cells. While SLX4 was dispensable for RAD52-mediated ALT telomere synthesis in G2, combined SLX4 and RAD52 loss resulted in elevated telomere loss, unresolved telomere recombination intermediates, and mitotic infidelity. These findings establish that RAD52 and SLX4 mediate distinct postreplicative DNA repair processes that maintain ALT telomere stability and cancer cell viability.