Structural and kinetic insights into tRNA promoter engagement by yeast general transcription factor TFIIIC.

Transcription of transfer RNA (tRNA) genes by RNA polymerase (Pol) III requires the general transcription factor IIIC (TFIIIC), which recognizes intragenic A-box and B-box DNA motifs of type II gene promoters. However, the underlying mechanism has remained elusive, in part due to missing structural information for A-box recognition. In this study, we use single-particle cryogenic electron microscopy (cryo-EM) and single-molecule fluorescence resonance energy transfer (smFRET) to reveal structural and real-time kinetic insights into how the 520-kDa yeast TFIIIC complex engages A-box and B-box DNA motifs in the context of a tRNA gene promoter.

JWST sighting of decameter main-belt asteroids and view on meteorite sources.

Asteroid discoveries are essential for planetary-defense efforts aiming to prevent impacts with Earth, including the more frequent megaton explosions from decameter impactors. While large asteroids (≥100 km) have remained in the main belt since their formation, small asteroids are commonly transported to the near-Earth object (NEO) population. However, due to the lack of direct observational constraints, their size-frequency distribution -which informs our understanding of the NEOs and the delivery of meteorite samples to Earth-varies significantly among models.

Method for measuring the transpiration resistance of fruit and vegetables.

This investigation explores the intricate relationship between postharvest quality losses in fruit and vegetables and the dynamic interplay of transpiration and respiration activities. It underscores the profound impact of inherent produce properties and postharvest environmental conditions on transpiration, inducing changes in both external appearance and internal quality, notably wilting. Despite their common use, produce-specific transpiration coefficients encounter limitations due to diverse assumptions in calculations.