PCH2 is an essential nucleolar component of the pachytene checkpoint, which prevents chromosome segregation when recombination and chromosome synapsis are defective (2). Nucleolar localization of Pch2p depends on silencing factors Sir2p and Dot1p, mutation of each of which disrupts the pachytene checkpoint (2, 1). Mutation of PCH2 relieves the checkpoint-induced pachytene arrest of zip1, zip2, and dmc1 mutants, resulting in chromosome missegregation and low spore viability (1). Pch2p also functions to repress interhomolog recombination in the ribosomal DNA during meiosis by excluding the meiosis-specific DNA binding protein Hop1p, which is required for homologous chromosome synapsis and the formation of chiasmata (1). In some situations, Pch2p will also localize to telomeres in a Sir3p-dependent manner and provide checkpoint function, thereby linking the nucleolus, chromatin silencing, and the pachytene checkpoint (1).

Last updated: 2004-07-01