The conserved eukaryotic THO-TREX complex acts at the interface between transcription and mRNA export and affects transcription-associated recombination. To investigate the interdependence of nuclear mRNA processes and their impact on genomic integrity, we analyzed transcript accumulation and recombination of 40 selected mutants covering representative steps of the biogenesis and export of the messenger ribonucleoprotein particle (mRNP). None of the mutants analyzed shared the strong transcript-accumulation defect and hyperrecombination of THO mutants. Nevertheless, mutants in 3' end cleavage/polyadenylation, nuclear exosome, and mRNA export showed a weak but significant effect on recombination and transcript accumulation. Mutants of the nuclear exosome (rrp6) and 3' end processing factors (rna14 and rna15) showed inefficient transcription elongation and genetic interactions with THO. The results suggest a tight interdependence among mRNP biogenesis steps and transcription and an unexpected effect of the nuclear exosome and the cleavage/polyadenylation factors on transcription elongation and genetic integrity.

The aim of this study is to evaluate the modification of the excretory portion and its comparison with the acinus, on stimulating the rat submaxillary gland with noradrenaline and isoproterenol. Stimulation of the submaxillary gland with these drugs for a period of 10 min produces different effects in the acinus and excretory portion. The secretory granules do not show reorganisation of their contents after stimulation with isoproterenol, while in the acinus the material is reorganised forming concentric laminae. After stimulation with noradrenaline, the acinar lumen increases its diameter with respect to the control groups while this same stimulus does not modify the diameter of the ductal lumen. After stimulation with noradrenaline the extracellular spaces are consistently obliterated in all ducts except the striated duct, in which the behaviour is variable as in the acinus. In these two latter cases, the extracellular spaces are visible in some cases and not in others. Stimulation with noradrenaline is a potent stimulus of synthesis in both the granular undulated duct and the striated undulated duct, while in the acinus this effect is produced by isoproterenol.