B-Family Subunits of PP2A Orchestrate Septation and Conidiation in Aspergillus nidulans
Protein phosphatase 2A (PP2A) is a conserved heterotrimeric protein phosphatase that regulates multiple aspects of cell growth and metabolism in eukaryotic cells. Zhong and Jiang et al. (p. 1494–1506) identified two B-family subunits of PP2A-ParA and -PabA required for hyphal growth, conidiation, and self-fertilization through regulation of PP2A activities in Aspergillus nidulans. ParA locates to septa, while PabA colocalizes with nuclei. ParA counteracts with PabA during the septation process. By contrast, ParA functions synthetically with PabA during hyphal growth. The finding indicates that B-family subunits of PP2A coordinate with each other spatially and temporally and play unique and comprehensive functions in the filamentous fungus A. nidulans.
All Are Not Equal: Mechanistic Differences between Tetrahymena Genome Processing Events
Tetrahymena undergo two chromosome processing events during sexual reproduction: internal eliminated sequence (IES) excision and chromosome breakage with new telomere addition. IES excision occurs via a well-characterized RNAi-based pathway but it has been unclear whether chromosome breakage involves the same mechanism. Cranert et al. (p. 1519–1529) have now shown that the telomere protein paralog Pot2 localizes to sites of chromosome breakage (CBSs) but not to IES or telomeres. Moreover, CBSs fail to accumulate histone modifications that are essential for IES removal. Thus, the work demonstrates that IES excision and chromosome breakage are mechanistically different, and it also reveals a novel role for Pot1 family members.
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