The Lsm1-7/Pat1 complex binds to stress-activated mRNAs and modulates the response to hyperosmotic shock

RNA-binding proteins (RBPs) establish the cellular fate of a transcript, but an understanding of these processes has been limited by a lack of identified specific interactions between RNA and protein molecules. Using MS2 RNA tagging, we have purified proteins associated with individual mRNA species induced by osmotic stress, STL1 and GPD1. We found members of the Lsm1-7/Pat1 RBP complex to preferentially bind these mRNAs, relative to the non-stress induced mRNAs, HYP2 and ASH1. To assess the functional importance, we mutated components of the Lsm1-7/Pat1 RBP complex and analyzed the impact on expression of osmostress gene products. We observed a defect in global translation inhibition under osmotic stress in pat1 and lsm1 mutants, which correlated with an abnormally high association of both non-stress and stress-induced mRNAs to translationally active polysomes. Additionally, for stress-induced proteins normally triggered only by moderate or high osmostress, in the mutants the protein levels rose high already at weak hyperosmosis. Analysis of ribosome passage on mRNAs through co-translational decay from the 5' end (5P-Seq) showed increased ribosome accumulation in lsm1 and pat1 mutants upstream of the start codon. This effect was particularly strong for mRNAs induced under osmostress. Thus, our results indicate that, in addition to its role in degradation, the Lsm1-7/Pat1 complex acts as a selective translational repressor, having stronger effect over the translation initiation of heavily expressed mRNAs. Binding of the Lsm1-7/Pat1p complex to osmostress-induced mRNAs mitigates their translation, suppressing it in conditions of weak or no stress, and avoiding a hyperresponse when triggered

Massive spin-half particle in the de Sitter universe

With the use of the Newman-Penrose spin coefficients, the radial part of the electrom equation in the de Sitter-Schwarzschild space is separated, and the transmission coefficient is calculated when the metric is specialized to the de Sitter case. Two different solutions of the radial equation are given. In the first one, the wavenumber corresponds to the flat space value; i.e., k2=ω2−m2, where ω is the energy and m is the rest mass of the particle. In this case, when ω»m, the transmission coefficient Γ becomes zero whereas, when ω→m, it is finite and is zero only for the lowest angular momentum state. In the second solution, k2 is found to involve the angular momentum. Γ in this case, exhibits a resonance phenomenon and becomes zero only for certain values of the energy or of the mass; one instance when Γ becomes zero is when ω→m, l=½ and k2= m2/4. When m = 0, both expressions for Γ correspond to the value for the massless neutrino