Fission Yeast Dma1 Is Involved In Polar Growth During Starvation Exit By Mediating The Ubiquitination Of Tip1

Fission yeast(Schizosaccharomyces pombe)is a typical polar growing organism that initially undergoes monopolar growth until G2 phase when it turns on bipolar growth(NETO).The microtubule plus-end tracking protein complex?Tips member Tipl plays an important role in NETO.It supervises the growth of interphase microtubules along the cell axis,ensuring that polar growth factors are transported to the cell poles.Dmal is a fission yeast spindle assembly checkpoint(SAC)protein,and it is also an E3 ubiquitin ligase,which has been reported in ubiquitinating SIN pathway member Sid4 at the spindle body(SPB),inhibits SIN pathway and thereby prevents cytokinesis.Our previous study showed that Dmal was located at the septum and SPB,which has been reported,and also had a weak localization at the poles of the cell.DmaI physically interacts with Tipl.After Dmal deletion,the le'vel of Tipl is increased.In this study,by adding double mNeonGreen to the C-terminus of Dmal,the localization of Dmal at the end is more clearly,and it is observed that Dmal colocalized with Tip1 at the poles of the cell.Our results showed that dmal d does not cause increaseed localization of Tipl in cells under vegetative growth.However,during the starvation exit,we observed that Tipl-tdTomato accumulated in the dmal ? strain at the poles of the cell,and the cell growth rate and bipolar recovery rate were also significantly faster than the wild type.In addition,we also observed the tipl25K-25R mutant,which has all mutations in the lysine site and cannot be ubiquitinated.It was found that,we could not see the increaseed localization of Tipl25k-25R-tdTomato neither under vegetative growth nor after starvation exit,but we found that the mutant produced a certain proportion of T-type cells during the starvation exit.This suggests those two mutant have a different effect on cells.At the same time,we found that the cells did not synthesize new Tipl during the the starvation exit.Finally,we also looked for another E3 ubiquitin ligase SPBC15C4.06c,and the ubiquitination of Tipl completely disappeared after dmal and SPBC15C4.06c double deletion.Taken together,our data suggest that fission yeast Dmal is involved in maintaining the polar growth rate at a proper pace during exit from starvation.