CENP-A gene replacement demonstrates that Ser68phos and Lys124ub are dispensable Ser68phos and Lys124ub are not required to maintain centromeres indefinitely CENP-A without Ser68phos or Lys124ub mediates centromeric chromatin assembly in G1 Ser68phos and Lys124ub are dispensable for early steps in centromere establishment