Secretory defects cause transcriptional repression of ribosome biogenesis in Saccharomyces cerevisiae. However, the molecular mechanism underlying secretory defect-induced transcriptional repression of ribosome biogenesis remains to be fully elucidated. In this study, we demonstrated that the Arp2/3 complex was required for reduction of ribosome protein gene expression in response to defective secretion by addition of tunicamycin. Two cmd1 mutants, cmd1-228 and cmd1-239 that cause mislocalization of calmodulin and defective mitotic spindle formation, respectively, failed to interact with Arc35, a component of the Arp2/3 complex. These mutants also caused defects in the reduction of ribosome protein gene expression induced by secretory blockade. A mutation in TUB4 (tub4-1), whose product has an essential function in microtubule organization, showed a similar response. In addition, we showed that the response to a secretory defect required SUN protein Mps3, which was localized at the nuclear envelope and involved in spindle pole body assembly. These results suggest that the Arp2/3 complex is required to transmit signals resulting from secretory blockade, and that the spindle pole body functions as a transit point from cytoplasm to Mps3 at the nuclear envelope. Copyright © 2016 John Wiley & Sons, Ltd.

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Journal Article

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Yabuki Y, Katayama M, Kodama Y, Sakamoto A, Yatsuhashi A, Funato K, Mizuta K

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