Figures & data
Figure 1. Roles of Ebp2 and Rrs1 at the nuclear periphery and summary of phenotypes in each condition. (A) Ebp2 and Rrs1 localize to the perinuclear region through Mps3, and thereby serve a structural function in the nucleus. Ebp2, Rrs1 and Mps3 are associated with the silent information factor Sir4, and function in telomere clustering in S phase cells and silencing. (B) Mutant forms of Ebp2 and Rrs1 lose association with the nuclear periphery at the restrictive temperature, thereby leading to the loss of the integrity of the nuclear envelope. Telomeres remained localized to the nuclear envelope but lost the cluster formation in S phase cells and the silent domain organization. (C) The ectopic expression of Mps3-N′ leads Ebp2 and Rrs1 away from the nuclear periphery, thereby compromising their telomeric roles and the structural role at the nuclear periphery. Mps3-N′ also titrate Est1, a component of telomerase which is required for Ku-dependent telomere tethering in S phase, from the perinuclear binding sites.Citation21 (D) The lack of Sir4 does not affect the interaction of Ebp2 and Rrs1 with Mps3 and the perinuclear localization of Ebp2. Telomeres are detached from the nuclear periphery due to the absence of Sir4. The perinuclear Ebp2 and Rrs1 is sufficient for providing the structural role independently of telomeres. ONM, outer nuclear membrane; INM, inner nuclear membrane; M-N’, Mps3-N′; E/R, Ebp2 and Rrs1; NE, nuclear envelope; Tel., telomere; gray ellipse, unknown proteins constituting the perinuclear protein network; white circle, telomeric complex of Yku70/80 and telomerase.
Figure 2. Two states of Ebp2 and Rrs1 in the nucleus. (A) Ebp2 and Rrs1 interact with each other. Freely diffusible forms of Ebp2 and Rrs1 in the nucleolus have essential functions in biogenesis of the 60S ribosomal subunit. Rrs1 and Rpf2 are necessary for incorporation of 5S rRNA and ribosomal proteins L5 and L11 into pre-ribosomes. (B) Ebp2 and Rrs1 form the complex with Mps3 at the nuclear periphery and act as a complex playing roles in the structural maintenance of the nucleus and the telomere clustering and silencing. Gray blank ellipse, unknown proteins constituting perinuclear protein network.
