Molecular Biology of the Cell
Molecular Biology of the Cell
5 years ago

The meiosis-specific Cdc20 family-member Ama1 promotes binding of the Ssp2 activator to the Smk1 MAP kinase.

Aviva Diamond, Edward Winter, Aaron M Neiman, Timothy Philips, Chong Wai Tio, Gregory Omerza
Smk1 is a meiosis-specific MAP kinase (MAPK) in budding yeast that is required for spore formation. It is localized to prospore membranes (PSMs), the structures that engulf haploid cells during meiosis II (MII). Similar to canonically activated MAPKs, Smk1 is controlled by phosphorylation of its activation-loop threonine (T) and tyrosine (Y). However, activation loop phosphorylation occurs via a non-canonical two-step mechanism in which 1- the cyclin-dependent kinase activating kinase Cak1 phosphorylaytes T207 during MI and 2- Smk1 autophosphorylates Y209 as MII draws to a close. Autophosphorylation of Y209 and catalytic activity for substrates require Ssp2, a meiosis-specific protein that is translationally repressed until anaphase of MII. Ama1 is a meiosis-specific targeting subunit of the anaphase promoting complex/cyclosome (APC/C) that regulates multiple steps in meiotic development including exit from meiosis II. Here we show that Ama1 activates autophosphorylation of Smk1 on Y209 by promoting formation of the Ssp2/Smk1 complex at PSMs. These findings link meiotic exit to Smk1 activation and spore wall assembly.

Publisher URL: http://doi.org/10.1091/mbc.E17-07-0473

DOI: 10.1091/mbc.E17-07-0473

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