Transcription initiation factor IIB involves in Schwann cell differentiation after rat sciatic nerve crush

Histone Chaperone Nrp1 Mutation Affects the Acetylation of H3K56 in Tetrahymena thermophila

Histone modification and nucleosome assembly are mainly regulated by various histone-modifying enzymes and chaperones. The roles of histone-modification enzymes have been well analyzed, but the molecular mechanism of histone chaperones in histone modification and nucleosome assembly is incompletely understood. We previously found that the histone chaperone Nrp1 is localized in the micronucleus (MIC) and the macronucleus (MAC) and involved in the chromatin stability and nuclear division of Tetrahymena thermophila. In the present work, we found that truncated C-terminal mutant HA-Nrp1^TrC abnormally localizes in the cytoplasm. The truncated-signal-peptide mutants HA-Nrp1^TrNLS1 and HA-Nrp1^TrNLS2 are localized in the MIC and MAC. Overexpression of Nrp1^TrNLS1 inhibited cellular proliferation and disrupted micronuclear mitosis during the vegetative growth stage. During sexual development, Nrp1^TrNLS1 overexpression led to abnormal bouquet structures and meiosis arrest. Furthermore, Histone H3 was not transported into the nucleus; instead, it formed an abnormal speckled cytoplastic distribution in the Nrp1^TrNLS1 mutants. The acetylation level of H3K56 in the mutants also decreased, leading to significant changes in the transcription of the genome of the Nrp1^TrNLS1 mutants. The histone chaperone Nrp1 regulates the H3 nuclear import and acetylation modification of H3K56 and affects chromatin stability and genome transcription in Tetrahymena.

Increased Expression of TBP/TFIID after spinal cord injury in adult rats

Transcription factor IID (TFIID), as a general transcription factor, plays a pivotal role in the preinitiation complex (PIC) assembly and transcription initiation by recruiting RNA polymerase II to the promoter. The TFIID complex contains the TATA-box binding protein (TBP) and a group of conserved TAF proteins. However, its distribution and function in the central nervous system (CNS) are more diverse than previously understood. Here, we mainly investigated the spatiotemporal expression and cellular localization of TBP/TFIID during spinal cord injury (SCI) in adult rats. Western blot analysis revealed that TBP/TFIID was present in normal rat's spinal cord. It gradually increased, reached a peak at the third day after SCI, and then decreased. We observed that TBP/TFIID was widely distributed in spinal cord, mainly in neurons and glial cells. In addition, Western blot detection also showed that the third day post-injury was the proliferation peak indicated by the elevated expression of proliferating cell nuclear antigen (PCNA), a marker of proliferating cells. Importantly, injury-induced expression of TBP/TFIID was colabelled by PCNA showed the increase of TBP/TFIID expression in proliferating astrocytes and microglia. Collectively, we hypothesize that TBP/TFIID may be implicated in the proliferation of astrocytes and microglia and the recovery of neurological outcomes.

A new paradigm for transcription factor TFIIB functionality

Experimental and bioinformatic studies of transcription initiation by RNA polymerase II (RNAP2) have revealed a mechanism of RNAP2 transcription initiation less uniform across gene promoters than initially thought. However, the general transcription factor TFIIB is presumed to be universally required for RNAP2 transcription initiation. Based on bioinformatic analysis of data and effects of TFIIB knockdown in primary and transformed cell lines on cellular functionality and global gene expression, we report that TFIIB is dispensable for transcription of many human promoters, but is essential for herpes simplex virus-1 (HSV-1) gene transcription and replication. We report a novel cell cycle TFIIB regulation and localization of the acetylated TFIIB variant on the transcriptionally silent mitotic chromatids. Taken together, these results establish a new paradigm for TFIIB functionality in human gene expression, which when downregulated has potent anti-viral effects.

Changes in the BAG1 expression of Schwann cells after sciatic nerve crush

Bcl-2-associated athanogene-1 (BAG1), a co-chaperone for Hsp70/Hsc70, is a multifunctional protein, which has been shown to suppress apoptosis and enhance neuronal differentiation. However, the expression and roles of BAG1 in peripheral system lesions and repair are still unknown. In this study, we investigated the dynamic changes in BAG1 expression in an acute sciatic nerve crush model in adult rats. Western blot analysis revealed that BAG1 was expressed in normal sciatic nerves. BAG1 expression increased progressively after sciatic nerve crush, reached a peak 2 weeks post-injury, and then returned to the normal level 4 weeks post-injury. Spatially, we observed that BAG1 was mainly expressed in Schwann cells and that BAG1 expression increased in Schwann cells after injury. In vitro, we found that BAG1 expression increased during the cyclic adenosine monophosphate (cAMP)-induced Schwann cell differentiation process. BAG1-specific siRNA inhibited cAMP-induced Schwann cell differentiation. In conclusion, we speculated that BAG1 was upregulated in the sciatic nerve after crush, which was associated with Schwann cell differentiation.