UV damage-induced RNA polymerase II stalling stimulates H2B deubiquitylation

Histone H2B monoubiquitylation plays an important role in RNA polymerase II (RNAPII) elongation. Whether this modification responds to RNAPII stalling is not yet known. We report that both yeast and human cells undergo a rapid and significant H2B deubiquitylation after exposure to UV irradiation. This deubiquitylation occurs concurrently with UV-induced transcription arrest and is significantly reduced in a DNA damage-bypassing RNAPII yeast mutant. Consistent with these results, yeast deubiquitylases Ubp8 and Ubp10 are associated with the RNAPII complex. Moreover, simultaneous deletion of Ubp8 and Ubp10 leads to a lack of H2B deubiquitylation after UV exposure. Consequently, nucleotide excision repair at an actively transcribed gene locus is decreased, whereas UV-induced RNAPII degradation is increased in ubp8Δubp10Δ mutant cells. These results indicate that eukaryotic cells respond to RNAPII arrest by deubiquitylating H2B to coordinate DNA repair and RNAPII degradation

Screening of ligninolytic fungi for biological pretreatment of lignocellulosic biomass

To identify white rot fungi with high potential in biological pretreatment of lignocellulosic biomass, preliminary screening was carried out on plates by testing different strains for their ability to oxidize guaiacol and decolorize the dyes azure B and Poly R-478. Of the 86 strains screened, 16 were selected for secondary screening for their ligninolytic ability; however, low manganese peroxidase activity and no lignin peroxidase activity were detected. Strain BBEL0970 proved to be the most efficient in laccase production and was subsequently identified as Trametes versicolor by analysis of the ribosomal DNA internal transcribed spacer gene sequence. In combining laccase production with biological pretreatment, the replacement of glucose with barley straw significantly improved the laccase activity by up to 10.3 U/mL, which provided evidence toward potential utilization of barley straw in laccase production by BBEL0970. Simultaneously, comparison by thermogravimetric analysis of the untreated and pretreated barley straw in liquid fermentation of laccase also demonstrated the high potential of BBEL0970 in biological pretreatment of lignocellulosic biomass. This work sheds light on further exploration on the integrated process of low-cost laccase production and efficient biological pretreatment of barley straw by T. versicolor BBEL0970