The Cohesin Regulatory Factor Pds5 Interacts With Proteasomes To Control Chromosome Axis Length During Meiosis

Meiosis is essential for sexual reproduction in eukaryotes.During meiosis,diploid cells undergo a single round of DNA replication and two successive rounds of chromosome segregation.Homologous chromosomes and sister chromatids segregate during Meiosis I and Meiosis II,respectively,to produce gametes with half of the number of chromosomes,ensuring the genetic stability of the offspring.Chromosome structure and morphology undergo dramatic change during meiosis,especially along with homolog pairing,synapsis,and segregation to ensure the proper progression of this specific cell cycle.The cohesin complex involves in this important progress.Pds5,an important regulatory factor of cohesin complex,localizes on chromosome axes and regulates chromosome axis length at meiotic prophase I.However,how Pds5 regulates the axis length is not clear.In this thesis,we use Sacch aromyces cerevisiae as experimental materials.Based on the verification of the interaction between Pds5 and proteasome,the mutant strains were constructed to explore the function of the interaction between Pds5 and proteasome in meiosis.The main results are as followings:1.Pds5 interacts with proteasomes and recruits them to chromosomes during meiosis.Our previous results on Pds5 immunoprecipitation-mass spectrometry showed that Pds5 may interact with proteasomes.Here,the interaction between Pds5 and proteasome subunits Prel,Rpn6,and Rpt2 was confirmed by using yeast two-hybrid and co-immunoprecipitation.Moreover,the N terminal containing the first 700 amino acid residues of Pds5 mediates the interaction.Error-prone PCR mediated random mutagenesis indicates many amino acids on the fragment containing 355-701AA are required for the interaction between Pds5 and Rpn6.Further experiments showed that most proteasomes cannot be recruited to chromosomes in the absence of Pds5,however,the localization of Pds5 on chromosomes is only slightly affected in the absence of proteasome subunits Prel or Rpn6.These results suggest that Pds5 interacts with proteasomes to recruit them to chromosomes during meiosis.2.Pds5 interacts with proteasome to regulate chromosome axis length during meiosis.Yeast strains bearing the meiosis-specific depletion of proteasome subnit Prel,Rpn6,or Rpt2 showed the similar decreased chromosome axis length as the meiosis-specific depletion of Pds5 strain during meiosis.The double mutant with meiosis-specific depletion of Pds5 and one proteasome subunit also showed the similar axis length as any single mutant during meiosis.This result suggests that Pds5 regulate chromosome axis length by recruiting proteasomes to chromosomes during meiosis.Additionally,these proteasome mutants also showed delayed nuclear division and largely decreased sporulation frequency.In summary,we showed that Pds5 recruits proteasomes to regulate chromosome axis length during meiosis.These findings reveal a new role of proteasomes and elucides the mechanism of Pds5 regulating chromosome organization during meiosis.