Anti-Scl-70 Antigen polyclonal antibody

Ebola virus (EBOV) protein L (EBOL) acts as a viral RNA-dependent RNA polymerase. To better understand the mechanisms underlying the transcription and replication of the EBOV genome, we sought to identify cellular factors involved in these processes via their coimmunoprecipitation with EBOL and by mass spectrometry. Of 65 candidate proteins identified, we focused on DNA topoisomerase 1 (TOP1), which localizes to the nucleus and unwinds helical DNA. We found that in the presence of EBOL, TOP1 colocalizes and interacts with EBOL in the cytoplasm, where transcription and replication of the EBOV genome occur. Knockdown of TOP1 markedly reduced virus replication and viral polymerase activity. We also found that the phosphodiester bridge-cleaving and recombination activities of TOP1 are required for the polymerase activity of EBOL. These results demonstrate that TOP1 is an important cellular factor for the transcription and replication of the EBOV genome and, as such, plays a key role in the EBOV life cycle.

DNA topoisomerases modulate DNA topology to maintain chromosome superstructure and genome integrity, which is indispensable for DNA replication and RNA transcription. Their function in plant development still remains largely unknown. Here, we report a hitherto unidentified role of Topoisomerase I alpha (TOP1 alpha) in controlling flowering time in Arabidopsis (Arabidopsis thaliana). Loss of function of TOP1a results in early flowering under both long and short days. This is attributed mainly to a decrease in the expression of a central flowering repressor, FLOWERING LOCUS C (FLC), and its close homologs, MADS AFFECTING FLOWERING4 (MAF4) and MAF5, during the floral transition. TOP1a physically binds to the genomic regions of FLC, MAF4, and MAF5 and promotes the association of RNA polymerase II complexes to their transcriptional start sites. These correlate with the changes in histone modifications but do not directly affect nucleosome occupancy at these loci. Our results suggest that TOP1a mediates DNA topology to facilitate the recruitment of RNA polymerase II at FLC, MAF4, and MAF5 in conjunction with histone modifications, thus facilitating the expression of these key flowering repressors to prevent precocious flowering in Arabidopsis.