A homozygous KASH5 frameshift mutation causes diminished ovarian reserve, recurrent miscarriage, and non-obstructive azoospermia in humans

The meiosis-specific LINC complex, composed of the KASH5 and SUN1 proteins, tethers the moving chromosomes to the nuclear envelope to facilitate homolog pairing and is essential for gametogenesis. Here, we applied whole-exome sequencing for a consanguineous family with five siblings suffering from reproductive failure, and identified a homozygous frameshift mutation in KASH5 (c.1270_1273del, p.Arg424Thrfs*20). This mutation leads to the absence of KASH5 protein expression in testes and non-obstructive azoospermia (NOA) due to meiotic arrest before the pachytene stage in the affected brother. The four sisters displayed diminished ovarian reserve (DOR), with one sister never being pregnant but still having dominant follicle at 35 years old and three sisters suffering from at least 3 miscarriages occurring within the third month of gestation. The truncated KASH5 mutant protein, when expressed in cultured cells, displays a similar localization encircling the nucleus and a weakened interaction with SUN1, as compared with the full-length KASH5 proteins, which provides a potential explanation for the phenotypes in the affected females. This study reported sexual dimorphism for influence of the KASH5 mutation on human germ cell development, and extends the clinical manifestations associated with KASH5 mutations, providing genetic basis for the molecular diagnosis of NOA, DOR, and recurrent miscarriage.

LC-MS Guided Isolation of Bioactive Principles from Iris hookeriana and Bioevaluation of Isolates for Antimicrobial and Antioxidant Activities

The genus Iris is diverse both in the abundance of secondary metabolities as well as the biological activities. The rhizomes of Iris hookeriana exhibit significant anthelminthic activity against gastrointestinal nematodes of sheep. Although Iris hookeriana has been a subject of the study of so many phytochemical studies, yet we report some constituents for the first time from this plant using a different isolation approach. This manuscript presents the isolation, antimicrobial and antioxidant evaluation of bioactive principles from Iris hookeriana. LC-MS guided isolation technique was applied for the separation of target constituents. The isolates were characterised by spectral techniques and subjected to antioxidant evaluation by DPPH assay. Four compounds; resveratrol, resveratroloside, junipeginin C and isorhamnetin-3-O-neohesperidoside were isolated for the first time along with 3 known compounds viz piceid, irigenin and iridin from I. hookeriana using this approach. The antioxidant activity screening of the isolates revealed that all the 4 constituents isolated for the first time, have strong antioxidant potential with IC50 of 14.0 µg/ml (resveratroloside), 19.7 µg/ml (junipeginen C), 12.8 µg/ml (resveratrol) and 19.8 µg/ml (isorhamnetin-3-O-neohesperodoside). So it can be safely concluded that LC-MS guided isolation of chemical compounds from Iris hookeriana has furnished 4 antioxidant constituents. Thus Iris hookeriana can act as as a good source of wonder molecule resveratrol and its 2 glycosides, resveratrolside and piceid which upon hydrolysis can be converted into the parent drug resveratrol.

Binding of EBNA-1 to DNA creates a protease-resistant domain that encompasses the DNA recognition and dimerization functions

The Epstein-Barr virus nuclear antigen EBNA-1 is essential for replication of the viral DNA during latency. EBNA-1 binds as a dimer to palindromic recognition sequences within the plasmid origin of replication, ori-P. In this study, proteinase K susceptibility has been used to further characterize the DNA-binding domain of EBNA-1. Limited protease digestion of EBNA-1 (amino acids 408 to 641) generated a smaller DNA-binding species that had a degree of inherent protease resistance. When EBNA-1 was preincubated with a specific DNA probe, the protease resistance of the smaller binding species increased 100-fold, suggesting that the conformation of EBNA-1 changes on binding. The protease-resistant species comprised an 18-kDa polypeptide that was further cleaved at high levels of protease to 11- and 5.4-kDa products. A model of the proposed protease-resistant domain structure is presented. Constructions carrying serial, internal deletions across the 18-kDa domain were created. Each of the deletions perturbed dimerization ability and abolished DNA binding. These studies suggest that the DNA-binding and dimerization motifs of EBNA-1 lie within a conformationally discrete domain whose overall integrity is necessary for EBNA-1-DNA interaction.

Definition of the sequence requirements for binding of the EBNA-1 protein to its palindromic target sites in Epstein-Barr virus DNA

Interaction between the trans-acting DNA-binding protein EBNA-1 and cis-acting sequences in the ori-P region of Epstein-Barr virus DNA is required for maintenance of the viral plasmid state in latently infected B cells and is involved in the regulation of transcription during latency. In the Epstein-Barr virus genome, a total of 26 EBNA-1-binding sites occur within three clustered loci referred to as the family of repeats and dyad symmetry locus of ori-P and the separate BamHI-Q locus. Incubation of a bacterially expressed carboxy-terminal domain of EBNA-1 (28,000-molecular-weight EBNA-1 [28K EBNA-1]) with synthetic monomer and dimer consensus binding sites gave characteristic DNA-protein complexes in a mobility retardation assay. A similar approach with the naturally occurring Q locus confirmed that it contains two distinct but low-affinity binding sites. We then examined the precise sequence requirements for EBNA-1 binding, using a set of 30-base-pair oligonucleotides designed to contain symmetric point mutations within both halves of the palindromic target site. Analysis of all possible single substitutions between positions 1 and 10 in the consensus half-palindrome sequence revealed that positions 9 and 10 did not contribute to EBNA-1 binding and that considerable flexibility could be tolerated at positions 1 and 2. Positions 3 through 8 of the recognition site had the most stringent requirements, with transversions at these positions either reducing or eliminating binding. The relative spacing of the halves of the palindrome was also critical, since the addition or removal of 2 base pairs at the center of the sequence abolished binding. Similar results were obtained when a partially purified preparation of intact Raji EBNA-1 was substituted for the 28K EBNA-1, and the results were further supported by methylation interference studies which indicated contact points between EBNA-1 and the guanine residues at positions -8, -7, and +3 of the binding site. The three naturally occurring EBNA-1-binding loci have previously been shown to differ in their relative affinities for EBNA-1. The present study indicates that the sequence variations occurring within the family of repeats would not affect binding affinity, whereas certain base substitutions within the Q and dyad symmetry sites would be predicted to contribute to the observed lower affinities of these sites. An apparent Kd of 1.5 x 10(-11) M for binding of 28K EBNA-1 to a consensus recognition site was calculated from Scatchard analysis.