Nucleolar Protein Dnt1 Is Involved In RDNA Silencing By Influencing Condensin In Fission Yeast

In eukaryotes,the ribosome is responsible for all the protein synthesis in the cell,and nucleoli are the places of ribosomal RNA synthesis,processing and assembling.rDNA region is mainly composed of numerous tandem repeat sequences,and maintaining the stability and integrity of repetitive sequences in rDNA is critical for the normal physiological activities of the cells.rDNA silencing is that when a reporter gene normally transcripted by RNA PolII is inserted into the rDNA region,the expression of the gene will be significantly inhibited.The mechanisms of rDNA silencing can effectively inhibit gene transcription,avoid the homologous recombination between rDNA tandem repeats,maintain stability and integrity of rDNA region.In this study,we discovered that gene transcription is necessary for rDNA silencing regulated by the fission yeast nucleolar protein Dntl,and histone acetylation modification is probably not relevant to Dntl function.Nucleolar localization of Acrl(accumulation of condensin at rDNA)depends on Dntl.By use of the high-affinity between GBP and GFP,NCT complex(Nrcl-CKII-TAFs)artificially targeted at nucleolus can resuce rDNA silencing defects in dnt1?,which indicates that NCT complex has different functions in chromosome arm and nucleolus.Similarly,condensin artificially targeted at nucleolus can effectively reverse the rDNA silencing defects in dnt1?.Thus,our results showed that Dntl regulates rDNA silencing probably by controlling condensin function at nucleolus.