A genome-wide function of THSC/TREX-2 at active genes prevents transcription–replication collisions

The THSC/TREX-2 complex of Saccharomyces cerevisiae mediates the anchoring of transcribed genes to the nuclear pore, linking transcription elongation with mRNA export and genome stability, as shown for specific reporters. However, it is still unknown whether the function of TREX-2 is global and the reason for its relevant role in genome integrity. Here, by studying two TREX-2 representative subunits, Thp1 and Sac3, we show that TREX-2 has a genome-wide role in gene expression. Both proteins show similar distributions along the genome, with a gradient disposition at active genes that increases towards the 3 end. Thp1 and Sac3 have a relevant impact on the expression of long, G+C-rich and highly transcribed genes. Interestingly, replication impairment detected by the genome-wide accumulation of the replicative Rrm3 helicase is increased preferentially at highly expressed genes in the thp1Δ and sac3Δ mutants analyzed. Therefore, our work provides evidence of a function of TREX-2 at the genome-wide level and suggests a role for TREX-2 in preventing transcription– replication conflicts, as a source of genome instability derived from a defective messenger ribonucleoprotein particle (mRNP) biogenesis.Spanish Ministry of Economy and Competitiveness [BFU2010-16372]; Junta de Andalucía [CVI4567 and P12/BIO-1238]; European Union (FEDER); and a JAE predoctoral training grant from the Spanish Research Council (CSIC) [to J.M.S-P.]. Funding for open access charge: Spanish Ministry of Economy and Competitiveness [BFU2010-16372].Peer reviewe

Coherent control of molecular Rydberg wave packets.

New experiments and theory contributing to the understanding of the dynamics and control of molecular Rydberg wave packets are presented. An intuitive scheme for controlling the rotational quantum state of a Rydberg molecule is demonstrated experimentally. We determine the accumulated phase difference between the various components of a molecular electron wave packet, and then employ a sequence of phase-locked optical pulses to selectively enhance or depopulate specific rotational states. The angular momentum composition of the resulting wave packet, and the efficiency of the control scheme, is determined by calculating the multipulse response of the time dependent Rydberg populations. The dynamics of predissociating Rydberg electron wavepackets are observed using the optical Ramsey method. The time-resolved spectra are hydrogenic and are very well modeled by assuming that only one p Rydberg series contributes to the dynamics. This is in contrast with previous observations of autoionising Rydberg electron wave packets which show quite dramatic deviations from hydrogenic behaviour above the Born-Oppenheimer limit. The origin of these deviations lies in the interplay between electronic and molecular phase. By exploiting these phases we are able to control the ratio of predissociaton to autoionisation A multichannel quantum defect theory analysis of the Rydberg state of NO is undertaken. The analysis takes into account all the accessible series with / < 3 and all documented interseries interactions. This analysis is the most complete description of NO to date and will aid in the design of future coherent control experiments