Molecular Mechanism Underlying the Interaction of Typical Sac10b Family Proteins with DNA

The Sac10b protein family is regarded as a family of DNA-binding proteins that is highly conserved and widely distributed within the archaea. Sac10b family members are typically small basic dimeric proteins that bind to DNA with cooperativity and no sequence specificity and are capable of constraining DNA negative supercoils, protecting DNA from Dnase I digestion, and do not compact DNA obviously. However, a detailed understanding of the structural basis of the interaction of Sac10b family proteins with DNA is still lacking. Here, we determined the crystal structure of Mth10b, an atypical member of the Sac10b family from Methanobacterium thermoautotrophicum ΔH, at 2.2 Å. Unlike typical Sac10b family proteins, Mth10b is an acidic protein and binds to neither DNA nor RNA. The overall structure of Mth10b displays high similarity to its homologs, but three pairs of conserved positively charged residues located at the presumed DNA-binding surface are substituted by non-charged residues in Mth10b. Through amino acids interchanges, the DNA-binding ability of Mth10b was restored successfully, whereas the DNA-binding ability of Sso10b, a typical Sac10b family member, was weakened greatly. Based on these results, we propose a model describing the molecular mechanism underlying the interactions of typical Sac10b family proteins with DNA that explains all the characteristics of the interactions between typical Sac10b family members and DNA

The effects of in-plane and out-of-plane constraints on J-R curves for X80 steel: A study using clamped SENT specimens

In the present paper, an experimental program was carried out to develop J-R curves using clamped single edge notched tension (SENT) specimens. A wide range of geometrical parameter variations is considered including different crack depth to plate width ratios (a/W) and plate thickness to width ratios (B/W). The material studied is the oil and gas pipeline steel API X80. Power law curve fitting parameters and tearing modulus are obtained for the J-R curves using the unloading compliance (UC) method for the clamped SENT specimens. Moreover, in-plane and out-of-plane constraint effects on J-R curves using clamped SENT specimens are studied, the second terms in the Williams’ series expansion are used to quantify the constraint effects. Specifically, it is demonstrated that the normalized T11 and the independent portion of T33, which equals T33-νT11, can be used to quantify the in-plane and out-of-plane constraint effects, respectively. Comparisons show that the constraint dependent

Current Understandings of Core Pathways for the Activation of Mammalian Primordial Follicles

The mammalian ovary has two main functions—producing mature oocytes for fertilization and secreting hormones for maintaining the ovarian endocrine functions. Both functions are vital for female reproduction. Primordial follicles are composed of flattened pre-granulosa cells and a primary oocyte, and activation of primordial follicles is the first step in follicular development and is the key factor in determining the reproductive capacity of females. The recent identification of the phosphatidylinositol 3 kinase (PI3K)/phosphatase and tensin homolog deleted on chromosome 10 (PTEN) signaling pathway as the key controller for follicular activation has made the study of primordial follicle activation a hot research topic in the field of reproduction. This review systematically summarizes the roles of the PI3K/PTEN signaling pathway in primordial follicle activation and discusses how the pathway interacts with various other molecular networks to control follicular activation. Studies on the activation of primordial follicles have led to the development of methods for the in vitro activation of primordial follicles as a treatment for infertility in women with premature ovarian insufficiency or poor ovarian response, and these are also discussed along with some practical applications of our current knowledge of follicular activation