Characterization of Knots and Links Arising From Site-specific Recombination on Twist Knots

We develop a model characterizing all possible knots and links arising from recombination starting with a twist knot substrate, extending previous work of Buck and Flapan. We show that all knot or link products fall into three well-understood families of knots and links, and prove that given a positive integer $n$, the number of product knots and links with minimal crossing number equal to $n$ grows proportionally to $n^5$. In the (common) case of twist knot substrates whose products have minimal crossing number one more than the substrate, we prove that the types of products are tightly prescribed. Finally, we give two simple examples to illustrate how this model can help determine previously uncharacterized experimental data.Comment: 32 pages, 7 tables, 27 figures, revised: figures re-arranged, and minor corrections. To appear in Journal of Physics

Coiling Instability of Multilamellar Membrane Tubes with Anchored Polymers

We study experimentally a coiling instability of cylindrical multilamellar stacks of phospholipid membranes, induced by polymers with hydrophobic anchors grafted along their hydrophilic backbone. Our system is unique in that coils form in the absence of both twist and adhesion. We interpret our experimental results in terms of a model in which local membrane curvature and polymer concentration are coupled. The model predicts the occurrence of maximally tight coils above a threshold polymer occupancy. A proper comparison between the model and experiment involved imaging of projections from simulated coiled tubes with maximal curvature and complicated torsions.Comment: 11 pages + 7 GIF figures + 10 JPEG figure

Point mutations in the Rpb9-homologous domain of Rpc11 that impair transcription termination by RNA polymerase III

RNA polymerase III recognizes and pauses at its terminator, an oligo(dT) tract in non-template DNA, terminates 3′ oligo(rU) synthesis within this sequence, and releases the RNA. The pol III subunit Rpc11p (C11) mediates RNA 3′–5′ cleavage in the catalytic center of pol III during pausing. The amino and carboxyl regions of C11 are homologous to domains of the pol II subunit Rpb9p, and the pol II elongation and RNA cleavage factor, TFIIS, respectively. We isolated C11 mutants from Schizosaccharomyces pombe that cause pol III to readthrough terminators in vivo. Mutant RNA confirmed the presence of terminator readthrough transcripts. A predominant mutation site, F32, resides in the C11 Rpb9-like domain. Another mutagenic approach confirmed the F32 mutation and also isolated I34 and Y30 mutants. Modeling Y30, F32 and I34 of C11 in available cryoEM pol III structures predicts a hydrophobic patch that may interface with C53/37. Another termination mutant, Rpc2-T455I, appears to reside internally, near the RNA–DNA hybrid. We show that the Rpb9 and TFIIS homologous mutants of C11 reflect distinct activities, that differentially affect terminator recognition and RNA 3′ cleavage. We propose that these C11 domains integrate action at the upper jaw and center of pol III during termination

Well-being as a Function of Person-Country Fit in Human Values

It is often assumed that incongruence between individuals’ values and those of their country is distressing, but the evidence has been mixed. Across 29 countries, the present research investigated whether well-being is higher if people’s values match with those of people living in the same country or region. Using representative samples, we find that person-country and person-region value congruence predict six well-being measures (e.g., emotional well-being, relationship support; N = 54,673). Crucially, however, value type moderates whether person-country fit is positively or negatively associated with well-being. People who value self-direction, stimulation, and hedonism more and live in countries and regions where people on average share these values report lower well-being. In contrast, people who value achievement, power, and security more and live in countries and regions where people on average share these values, report higher well-being. Additionally, we find that people who moderately value stimulation report the highest well-being