**Mmi1, the Yeast Ortholog of Mammalian Translationally Controlled Tumor Protein (TCTP), Negatively A**ff**ects Rapamycin-Induced Autophagy in Post-Diauxic Growth Phase**

### **Jana Vojtova \* and Jiri Hasek \***

Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, Prague 4 142 20, Czech Republic

**\*** Correspondence: jana.vojtova@biomed.cas.cz (J.V.); hasek@biomed.cas.cz (J.H.); Tel.: +420-241-062-504 (J.V.); +420-241-062-343 (J.H.)

Received: 15 November 2019; Accepted: 3 January 2020; Published: 7 January 2020

**Abstract:** Translationally controlled tumor protein (TCTP) is a multifunctional and highly conserved protein from yeas<sup>t</sup> to humans. Recently, its role in non-selective autophagy has been reported with controversial results in mammalian and human cells. Herein we examine the effect of Mmi1, the yeas<sup>t</sup> ortholog of TCTP, on non-selective autophagy in budding yeas<sup>t</sup> *Saccharomyces cerevisiae*, a well-established model system to monitor autophagy. We induced autophagy by nitrogen starvation or rapamycin addition and measured autophagy by using the Pho8Δ60 and GFP-Atg8 processing assays in WT, *mmi1*Δ, and in autophagy-deficient strains *atg8*Δ or *atg1*Δ. Our results demonstrate that Mmi1 does not affect basal or nitrogen starvation-induced autophagy. However, an increased rapamycin-induced autophagy is detected in *mmi1*Δ strain when the cells enter the post-diauxic growth phase, and this phenotype can be rescued by inserted wild-type *MMI1* gene. Further, the *mmi1*Δ cells exhibit significantly lower amounts of reactive oxygen species (ROS) in the post-diauxic growth phase compared to WT cells. In summary, our study suggests that Mmi1 negatively affects rapamycin-induced autophagy in the post-diauxic growth phase and supports the role of Mmi1/TCTP as a negative autophagy regulator in eukaryotic cells.

**Keywords:** Mmi1; TCTP; translationally controlled tumor protein; autophagy; reactive oxygen species; rapamycin; nitrogen starvation
