Histone association with DNA in eukaryotic cells forms the nucleosome core particle, the fundamental repeating subunit of chromatin. This association allows the DNA to be compacted into the nucleus.  Compaction prevents regulatory machinery from accessing the DNA for DNA-templated processes such as: DNA replication, transcription and repair. The cell must alter the structure of the chromatin to carry out these processes. Two mechanisms cells use are post-translational modifications to histones and the replacement of canonical histones with structural and functional variants. In <i>Saccharomyces cerevisiae</i>, the most abundant variant is the H2A variant H2A.Z. It remains unclear as to how the cell differentiates these two histones for placement in chromatin. We sought to identify specific residues on H2A.Z that distinguish it from H2A. We used two criteria to identify potentially important/distinguishing residues: 1) we identified residues that are well-conserved in H2A.Z and 2) we identified residues that are variant between H2A and H2A.Z. We targeted Threonine 87, Serine 111, and Serine 131. Using the NetPhos algorithm, we find there is a high probability each is phosphorylated. Mutation of the T87, but not S131 or S111, leads to sensitivity to caffeine and 6-Azauracil. We found that expression of the Gal1 gene is unaffected in the T87 mutant. Surprisingly, either deletion of H2A.Z or mutation of T87 leads to a sensitivity to rapamycin. RT-PCR of TOR signaling pathway genes TOR1 and STM1 were performed. We found these genes to be differentially expressed in the T87 mutant. Finally, we looked at expression of H2A.Z in these mutants. We find global and chromatin levels of H2A.Z to be significantly lowered in the T87 mutant.  Taken together, these findings indicate that T87 is important for the functionality of H2A.Z. We also find a potential role of H2A.Z in regulating the TOR signaling pathway.

Identification of functionally important residues in histone H2A.Z in <i>Saccharomyces cerevisiae</i>

2019 Spring National Meeting

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Identification of functionally important residues in histone H2A.Z in Saccharomyces cerevisiae