A common function for mRNA 5\u27 and 3\u27 ends in translation initiation in yeast

The mRNA poly(A) tail and its associated poly(A) binding protein (Pab1p) are ubiquitous in eukaryotes. The function of the poly(A) tail is to stabilize mRNA and to stimulate its translation. The development of a poly(A)- and cap-dependent yeast in vitro translation system has allowed us to understand how poly(A) stimulates translation. We find that Pab1p but not the cap binding protein eIF-4E is required for poly(A) tail-dependent translation, and that the Pab1p-poly(A) tail complex functions to recruit the 40S ribosomal subunit to the mRNA. These data introduce a new step into the pathway of translation initiation and merge the translational functions of the two ends of mRNA

The yeast Pan2 protein is required for poly(A)-binding protein-stimulated poly(A)-nuclease activity

The removal of the mRNA poly(A) tail in the yeast Saccharomyces cerevisiae is stimulated by the poly(A)binding protein (Pab1p). A large scale purification of the Pab1p-stimulated poly(A) ribonuclease (PAN) identifies a 76-kDa and two 135-Da polypeptides as candidate enzyme subunits. Antibodies against the Pan1p protein, which is the minor 135-kDa protein in the preparation, can immunodeplete Pan1p but not PAN activity. The protein sequence of the major 135-kDa protein, Pan2p, reveals a novel protein that was also found in the previously reported PAN purification (Sachs, A. B., and Deardorff, J. A. (1992) Cell 70, 961-973). Deletion of the non-essential PAN2 gene results in an increase of the average length of mRNA poly(A) tails in vivo, and a loss of Pab1p-stimulated PAN activity in crude extracts. These data confirm that Pan2p and not Pan1p is required for PAN activity, and they suggest that ribonucleases other than the Pab1p-stimulated PAN are capable of shortening poly(A) tails in vivo

Cosmic microwave background and parametric resonance in reheating

The variation of the perturbative 3-curvature parameter, \zeta, is investigated in the period of reheating after inflation. The two-field model used has the inflaton, with an extra scalar field coupled to it, and non-linear effects of both fields are included as well as a slow decay mechanism into the hydrodynamic fluid of the radiation era. Changes in \zeta occur and persist into the succeeding cosmic eras to influence the generation of the cosmic microwave background fluctuations.Comment: 21 pages, 6 figures.Corrects misprinted formula and 2 number

Spacetime Energy Decreases under World-sheet RG Flow

We study renormalization group flows in unitary two dimensional sigma models with asymptotically flat target spaces. Applying an infrared cutoff to the target space, we use the Zamolodchikov c-theorem to demonstrate that the target space ADM energy of the UV fixed point is greater than that of the IR fixed point: spacetime energy decreases under world-sheet RG flow. This result mirrors the well understood decrease of spacetime Bondi energy in the time evolution process of tachyon condensation.Comment: 25 pages, 4 figures, harvma

Bondi-Metzner-Sachs symmetry, holography on null-surfaces and area proportionality of "light-slice" entropy

It is shown that certain kinds of behavior, which hitherto were expected to be characteristic for classical gravity and quantum field theory in curved spacetime, as the infinite dimensional Bondi-Metzner-Sachs symmetry, holography on event horizons and an area proportionality of entropy, have in fact an unnoticed presence in Minkowski QFT. This casts new light on the fundamental question whether the volume propotionality of heat bath entropy and the (logarithmically corrected) dimensionless area law obeyed by localization-induced thermal behavior are different geometric parametrizations which share a common primordeal algebraic origin. Strong arguments are presented that these two different thermal manifestations can be directly related, this is in fact the main aim of this paper. It will be demonstrated that QFT beyond the Lagrangian quantization setting receives crucial new impulses from holography onto horizons. The present paper is part of a project aimed at elucidating the enormous physical range of "modular localization". The latter does not only extend from standard Hamitonian heat bath thermal states to thermal aspects of causal- or event- horizons addressed in this paper. It also includes the recent understanding of the crossing property of formfactors whose intriguing similarity with thermal properties was, although sometimes noticed, only sufficiently understood in the modular llocalization setting.Comment: 42 pages, changes, addition of new results and new references, in this form the paper will appear in Foundations of Physic

Cell elongation in the grass pulvinus in response to geotropic stimulation and auxin application

Horizontally-placed segments of Avena sativa L. shoots show a negative geotropic response after a period of 30 min. This response is based on cell elongation on the lower side of the leaf-sheath base (pulvinus). Triticum aestivum L., Hordeum vulgare L. and Secale cereale L. also show geotropic responses that are similar to those in Avena shoots. The pulvinus is a highly specialized organ with radial symmetry and is made up of epidermal, vascular, parenchymatous and collenchymatous tissues. Statoliths, which are confined to parenchyma cells around the vascular bundles, sediment towards the gravitational field within 10–15 min of geotropic stimulation. Collenchymatous cells occur as prominent bundle caps, and in Avena , they occupy about 30% of the volume of the pulvinus. Geotropic stimulation causes a 3- to 5-fold increase in the length of the cells on the side nearest to the center of the gravitational field. Growth can also be initiated in vertically-held pulvini by the application of indole-3-acetic acid, 1-naphthaleneacetic acid or 2.4-dichlorophenoxyacetic acid. 2.3.5.-triiodobenzoic acid interferes with growth response produced by geotropic stimulation as well as with the response caused by auxin application. Gibberellic acid and kinetin have no visible effect on the growth of the pulvinus. Polarization microscopy shows a unique, non-uniform stretching of the elongating collenchymatous cells. Nonelongated collenchymatous cells appear uniformally anisotropic. After geotropic stimulation or auxin application, they appear alternately anisotropic and almost isotropic. Such a pattern of cell elongation is also observed in collenchyma cells of geotropically-stimulated shoots of Rumex acetosa L., a dicotyledon.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47463/1/425_2004_Article_BF00385422.pd

One-step affinity purification of the yeast ribosome and its associated proteins and mRNAs.

We describe a one-step affinity method for purifying ribosomes from the budding yeast Saccharomyces cerevisiae. Extracts from yeast strains expressing only C-terminally tagged Rpl25 protein or overexpressing this protein in the presence of endogenous Rpl25p were used as the starling materials. The purification was specific for tagged 60S subunits, and resulted in the copurification of 80S subunits and polysomes, as well as ribosome-associated proteins and mRNAs. Two of these associated proteins, Mpt4p and Asc1p, were nearly stoichiometrically bound to the ribosome. In addition, the degree of mRNA association with the purified ribosomes was found to reflect the mRNA's translational status within the cell. The one-step purification of ribosome and its associated components from a crude extract should provide an important tool for future structural and biochemical studies of the ribosome, as well as for expression profiling of translated mRNAs