Functional Research Of Saccharomyces Cerevisiae Histone H2A Ser122 Phosphorylation And Histone H4 N-terminal Acetylation In Meiosis

Meiosis is an essential process of sexual reproduction in eukaryotes.It includes one round of DNA replication followed by two successive rounds of chromosome segregation to produce gametes with half of the parental chromosomes.During meiosis,homologous chromosomes(homologs)undergo pairing,synapsis,and recombination.Crossover recombination(CO)results in paternal and maternal DNA exchange flanking the CO site,which is the major resources for genetic diversity and also provides the mechanical linkage with the help of sister chromatid cohesion,which is required for the correct segregation of homologs.The nucleosome is the basic structural unit of the chromosome and is composed of histones and DNA.The amino-terminal of histone is exposed on the nucleosome surface,which is subjected to several kinds of post-translation modifications,such as methylation,acetylation,and phosphorylation.These modifications can regulate the interaction between histones and DNA,and between adjacent nucleosomes,by alteration the charge of amino acid residues.In addition,histone modifications can also be used as "tags" to recruit non-histone proteins to regulate other related biological processes.Lots of studies have shown that histone modifications play important roles in DNA transcription,DNA damage repair,and chromosome remodeling.However,the function of histone modifications in meiosis is still unclear.Clarification the function of histone modification in meiosis is helpful for the further understanding of the molecular mechanism of meiosis but also provides a theoretical basis for diagnosis and treatment of reproductive-related diseases.In this study,we used Saccharomyces cerevisiae to explore the function of histone H2A Ser122 phosphorylation,histone H4 N-terminal and relevant acetylation in meiosis.The function of H2A Ser122 phosphorylation in meiosis was studied by using hta S122D and hta S122A mutants,which mimic phosphorylated and non-phosphorylated states,respectively.We found that the nuclear division of hta S122D mutant was delayed,and the proportion of nuclear division was significantly decreased.In addition,sporulation and spore viability was significantly decreased.The hta S122A mutants have severer meiotic defects than hta S122D mutants,including much lower sporulation level and spore viability.These results indicate that the proper dynamics of phosphorylation and dephosphorylation of H2A Ser122 are essential for multiple aspects of meiosis,including nuclear division,recombination,synapsis,sporulation,and spore viability.To investigate the function of the histone H4 N-terminal in meiosis,we constructed the hhf N4-19? mutant.It was found that meiosis nuclear division is delayed,and the sporulation level was significantly reduced,indicating that the histone H4 N-terminal fragment plays important roles in meiosis.To further investigate whether its roles are related to the acetylation of lysine of amino acid residues at 5,8,12 and 16,we constructed the hhf K5,8,12,16Q and hhf K5,8,12,16R mutant to mimic acetylation state and non-acetylation state,by changing all of these four lysine amino acids to glutamine and arginine,respectively.The meiotic nuclear division in the mutants of hhf K5,8,12,16Q and hhf K5,8,12,16R is delayed,and the recombination,sporulation,spore viability are impaired.Moreover,hhf K5,8,12,16R mutant has severer meiotic defects.These results suggest that the proper dynamics of acetylation and deacetylation on these four amino acid residues play an important role during meiosis.In conclusion,histone H2A Ser122 phosphorylation and histone H4 amino termini acetylation play important roles in meiosis including recombination,synapsis,sporulation and spore viability.