Growth of the Mammalian Golgi Apparatus during Interphase

Abstract

During the cell cycle, genetic materials and organelles are duplicated to ensure there is sufficient cellular content for daughter cells. While Golgi growth in interphase has been observed in lower eukaryotes, the elaborate ribbon structure of the mammalian Golgi has made it challenging to monitor. Here we demonstrate the growth of the mammalian Golgi in its protein content and volume during interphase. Through ultrastructural analyses, physical growth of the Golgi was revealed to occur by cisternal elongation of the individual Golgi stacks. By examining the timing and regulation of Golgi growth, we establish that Golgi growth starts after passage through the cell growth checkpoint at late G1 phase and continues growing in a manner highly correlated with cell size growth. Finally, by identifying S6 kinase 1 as a major player in Golgi growth, we reveal the coordination between cell size and Golgi growth via activation of the protein synthesis machinery in early interphase.