Identification and sequence characterization of a 1.3 Kb EcoRI repeat fragment that harbors a DNA repair site of rat pachytene spermatocytes

Serum exosome-derived biomarkers for the early detection of oral squamous cell carcinoma

Blood exosomes help regulate communication between tumour cells, moderating their behaviour. We sought to determine the protein content in serum exosomes (SEs), to characterise SEs, and to discover novel clinical biomarkers of oral squamous cell carcinoma (OSCC). Differentially expressed proteins (DEPs) of OSCC were identified using proteomics and then analysed using bioinformatics, before validation using ELISA, IHC, and RT-PCR. The influence of SEs on oral cancer cells was detected using CCK-8 and migration assays. Twelve DEPs were found in SEs from OSCC. Four proteins were targeted for further verification. New biomarkers exhibiting high sensitivity and specificity in diagnosing OSCC comprised C-reactive protein (CRP), von willebrand factor (VWF), and leucine-rich alpha-2-glycoprotein (LRG). Combined biomarkers outperformed any single protein. We also demonstrated that tumour-derived exosomes promoted tumour cell migration, but not proliferation and apoptosis. Our study indicates that CRP, VWF, and LRG are potential clinically relevant OSCC biomarkers. OSCC-related SEs may help promote migration of oral cells.

Characterization of a mouse recombination hot spot locus encoding a novel non-protein-coding RNA

Our current knowledge of recombination hot spot activity in mammalian systems implicates a role for both the primary DNA sequence and the nature of the chromatin domain around it. In mice, the only recombination hot spots mapped to date have been confined to a cluster within the major histocompatibility complex (MHC) region. We present a high resolution analysis of a new recombination hot spot in the mouse genome which maps to mouse chromosome 8 C-D. Haplotype diversity analysis across 40 different strains of mice has enabled us to map recombination breakpoints to a 1-kb interval. This hot spot has a recombination intensity that is 10- to 100-fold above the genome average and has a mean gene conversion tract length of 371 bp. This meiotically active locus happens to be flanked by a transcribed region encoding a non-protein-coding RNA polymerase II transcript and the previously characterized repair site. Many of the primary DNA sequence features that have been reported for the mouse MHC hot spots are also shared by this hot spot locus and in addition, along with three other MHC hot spot loci, we show a new parallel feature of association of the crossover sites with the nuclear matrix.

Recombination analysis of the human minisatellite MsH42 suggests the existence of two distinct pathways for initiation and resolution of recombination at MsH42 in rat testes nuclear extracts

We have previously described a GC-rich human minisatellite, termed MsH42, which exists in two allelic forms, long and short. Here, we have identified a third allele of medium length and localized the MsH42 locus in the chromosome 15q25.1 inside an intron belonging to a gene of unknown function. The recombinogenic potential of the three alleles was assayed in vitro incubating pBR322-based constructs containing two copies of the minisatellite MsH42 with its flanking sequences, in the presence of rat testes nuclear extracts. This assay system was configured to monitor only reciprocal exchange type events and not gene conversion. All MsH42 allelic sequences enhanced intramolecular homologous recombination promoting high rates (approximately 76%) of equal crossover, the long allele showing the highest recombinogenic activity. Removal of the MsH42 long allele flanking sequences, which are identical in the three alleles, provoked a decrease in the enhancement of recombination and in the frequency of equal crossovers, suggesting that these sequences are important for the recombinogenic activity and for the correct pairing between homologous sequences. The occurrence of some complex recombination events within the minisatellite MsH42 suggests the existence of processes related to polymerase slippage and unwinding with reinvasion during the repair synthesis. Our findings point toward the existence of two distinct biochemical pathways for initiation and resolution of recombination at the minisatellite MsH42. Finally, the in vitro recombination system employed in this study could provide an approach to dissect processes of repetitive DNA instability and recombination.

A DNA polymerase alpha catalytic subunit is purified independently from the tissues at meiotic prometaphase I of a basidiomycete, Coprinus cinereus

A 135kDa DNA polymerase alpha lacking primase activity has been purified to near homogeneity from Coprinus meiotic tissues. The activity of the DNA polymerase was sensitive to aphidicolin and N-ethylmaleimide, but was insensitive to dideoxythymidine triphosphate. DNA synthesis was proceeded with a low processivity. Neither activity nor processivity were affected by PCNA in the presence or absence of KCI. Monovalent cation inhibited its activity. These biochemical properties are almost identical to those of Coprinus DNA polymerase alpha -primase complex. However, the 135kDa DNA polymerase did not use activated DNA as a template-primer, inconsistent with Coprinus DNA polymerase alpha-primase complex. The 135kDa DNA polymerase was purified from the tissues at meiotic pro-metaphase I, suggesting that the alpha- DNA polymerase-primase complex dissociates as the meiotic cell cycle progresses and only the catalytic subunit remains at this stage.