A novel connection between the Nuclear Pore Complex and The Cell Division Cycle in Saccharomyces cerevisiae:The Nucleoporins Nup84 and Nup188 are Significant to the Activity of the G1 Cyclin Cln3

Abstract

In Saccharomyces cerevisiae, commitment to cell division is largely regulated by a complex that contains the G1 cyclin Cln3. This complex must be actively moved from the cytoplasm to nucleus, where Cln3 functions in initiating the transcription of genes important in progression through the cell cycle. In order for Cln3 to enter the nucleus, it must pass through a large assembly of proteins known as the nuclear pore channel (NPC), which is embedded within the nuclear envelope. Three proteins of the NPC were previously defined as important in the localization of an artificial construct consisting of a portion of the Cln3 protein. This research identifies genetic interactions between full-length Cln3 and the NPC components Nup84, Nup188, and Nup2 to ascertain the relevance of these genes in regulated cell division. Cln3 activity is reduced in the absence of NUP84 and NUP188, but not in the absence of NUP2. The absence of NUP188 increases the relative frequency of unbudded cells, which suggests that the lack of the Nup188 protein delays passage through the G1 phase of the division cycle. The absence of NUP84 does not increase the frequency of unbudded cells, but rather increases the frequency of cells with aberrant morphologies. The investigation concludes that Nup84 and Nup188 are significant to the functionality of Cln3, while Nup2 is not. This research offers the first documentation of a physiological link between the function of the G1 cyclin Cln3 and the nuclear pore complex (NPC).