The 3' Pol II pausing at replication-dependent histone genes is regulated by Mediator through Cajal bodies' association with histone locus bodies.

Non-polyadenylated mRNAs of replication-dependent histones (RDHs) are synthesized by RNA polymerase II (Pol II) at histone locus bodies (HLBs). HLBs frequently associate with Cajal bodies (CBs), in which 3'-end processing factors for RDH genes are enriched; however, this association's role in transcription termination of RDH genes remains unclear. Here, we show that Pol II pauses immediately upstream of transcript end sites of RDH genes and Mediator plays a role in this Pol II pausing through CBs' association with HLBs. Disruption of the Mediator docking site for Little elongation complex (LEC)-Cap binding complex (CBC)-Negative elongation factor (NELF), components of CBs, interferes with CBs' association with HLBs and 3' Pol II pausing, resulting in increased aberrant unprocessed RDH gene transcripts. Our findings suggest Mediator's involvement in CBs' association with HLBs to facilitate 3' Pol II pausing and subsequent 3'-end processing of RDH genes by supplying 3'-end processing factors.

Thermal characteristics of second harmonic generation by phase matched calorimetry.

We analyze a solution of the heat equation for second harmonic generation (SHG) with a focused Gaussian beam and simulate the temperature rise in SHG materials as a function of the second harmonic power and the focusing conditions. We also propose a quantitative value of the heat removal performance of SHG devices, referred to as the effective heat capacity Cα in phase matched calorimetry. We demonstrate the inverse relation between Cα and the focusing parameter ξ, and propose the universal quantity of the product of Cα and ξ for characterizing the thermal property of SHG devices. Finally, we discuss the strategy to manage thermal dephasing in SHG using the results from simulations.

Thermal performance in high power SHG characterized by phase-matched calorimetry.

We proposed a method to determine device quality in heat removal. Temperature change depending on SH power was analyzed by fitting with a new model to characterize heat removal performance of SHG modules, named as phase-matched calorimetry (PMC). The thermal disposal performance of SHG devices was improved by combination of metal housing and reduced crystal aperture. With a tight aperture, we demonstrated a 19 W single-pass 532-nm SHG at a conversion efficiency of 26.5% in a 10-mm-long PPMgSLT crystal without saturation.