Kar5p is required for multiple functions in both inner and outer nuclear envelope fusion in Saccharomyces cerevisiae.
Bottom Line: Several kar5 mutant proteins localized properly but did not mediate Prm3p recruitment; other kar5 mutant proteins localized and recruited Prm3p but were nevertheless defective for nuclear fusion, demonstrating additional functions beyond Prm3p recruitment.We identified one Kar5p domain required for SPB localization, which is dependent on the half-bridge protein Mps3p.Finally, a split-GFP assay demonstrated that Kar5p localizes to both the inner and outer nuclear envelope.
Affiliation: Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544-1014.Show MeSH
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Mentions: To further understand how Kar5p might interact with other nuclear fusion proteins, we expressed Kar5-TM3-GFP in nuclear fusion mutants prm3Δ, kar2-1, and kar8Δ. In kar2-1 and kar8Δ shmoos, Kar5-TM3-GFP appeared normal; it enriched strongly at the SPB, and formed several bright puncta elsewhere on the nuclear envelope (Figure 4A). In contrast, in prm3Δ shmoos Kar5-TM3-GFP enriched strongly at the SPB, but did not form additional puncta, and instead was diffusely localized along the nuclear envelope and peripheral ER (Figure 4A). This suggested that Prm3p might have a role in restricting Kar5p to the nuclear envelope and causing it to aggregate.
Affiliation: Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544-1014.