Regulation of the Ysh1 endonuclease of the mRNA cleavage/polyadenylation complex by ubiquitinmediated degradation.

Mutation of the essential yeast protein Ipa1 has previously been demonstrated to cause defects in premRNA 3ʹ end processing and growth, but the mechanism underlying these defects was not clear. In this study, we show that the ipa1-1 mutation causes a striking depletion of Ysh1, the evolutionarily conserved endonuclease subunit of the 19-subunit mRNA Cleavage/Polyadenylation (C/P) complex, but does not decrease other C/P subunits. YSH1 overexpression rescues both the growth and 3ʹ end processing defects of the ipa1-1 mutant. YSH1 mRNA level is unchanged in ipa1-1 cells, and proteasome inactivation prevents Ysh1 loss and causes accumulation of ubiquitinated Ysh1. Ysh1 ubiquitination is mediated by the Ubc4 ubiquitin-conjugating enzyme and Mpe1, which in addition to its function in C/P, is also a RING ubiquitin ligase. In summary, Ipa1 affects mRNA processing by controlling the availability of the C/P endonuclease and may represent a regulatory mechanism that could be rapidly deployed to facilitate reprogramming of cellular responses.post-print4,60 M

The xerophilic genera Xerobiotus and Pseudohexapodibius (Macrobiotidae; Tardigrada): biodiversity, biogeography and phylogeny

The genera Xerobiotus and Pseudohexapodibius are xerophilic and characterized by reduced appendages and claws as adaptations to move between small interstices. To increase the knowledge of their biodiversity, biogeography and phylogeny, several specimens from European countries and Australia were analysed using an integrative approach, i.e. morphological, karyological and molecular studies (18S, 28S, cox1, cytb and ITS2). The phylogenetic position of Xerobiotus with respect to the three evolutionary lineages of Macrobiotus remains unchanged with respect to what was previously identified in the phylogeny of Macrobiotidae. The following new Xerobiotus species are described: Xerobiotus litus sp. nov., Xerobiotus arenosum sp. nov. and Xerobiotus reductus sp. nov. It is proposed that Macrobiotus naginae should be transferred to Xerobiotus (Xerobiotus naginae comb. nov.). Pseudohexapodibius degenerans clusters within Xerobiotus and shares morphological and genetic characters with this genus. Some discrepancies between genetic and phenotypic data are found among the analysed species. Even between the results obtained with analysed genes disagreements are found, with cox1 and cytb generally agreeing with phenotypic results more than ITS2. Genotypic and phenotypic data are useful tools for species identification, but they have to be evaluated critically to obtain reliable results

Analysis of light diffraction by azobenzene-based photoalignment layers

Photoalignment materials, such as the azobenzene-based PAAD series studied here, are becoming increasingly important in liquid crystal-based optical devices and displays. Yet their properties and, in particular, their response to light, are still not fully understood. We investigate, experimentally and theoretically, the photoinduced birefringence, the order parameter and the formation of surface relief gratings, as well as the diffraction caused by them. We show that some of the azobenzene PAAD materials are suitable for the formation of surface relief gratings with high modulation depth, while others exhibit strong photoinduced birefringence. The two effects are inversely correlated: the stronger the surface relief grating is, the weaker is photoinduced birefringence. Analytical formulas based on the Raman-Nath approximation and numerical simulations of Maxwell’s equations are used to quantify the diffraction caused by the induced diffraction gratings, showing excellent agreement between theory and experiment

A novel putative transcription factor protein MYT2 that preferentially binds supercoiled DNA and induces DNA synthesis in quiescent cells

Myelin transcription factor 2 (MYT2), a putative transcription factor found in the human central nervous system, was cloned from an expression cDNA library from human T-cells. MYT2 shares weak similarity to bacterial type I topoisomerases and shares 63% sequence identity to a replicase from Leuconostoc mesenteroides. MYT2 preferentially binds supercoiled DNA (scDNA). Incubation of MYT2 and scDNA at or above equal molar ratios generated topoisomer-like patterns that were abolished by deproteination. Thus, MYT2 appears to relax scDNA via a non-enzymatic mechanism. The banding pattern of MYT2–scDNA complexes was shown to be quantisized, saturable and sequence-independent. Microinjection of MYT2 mRNA induced Go growth-arrested NIH 3T3 cells to enter the S phase of the cell cycle.link_to_OA_fulltex