Figure 1

Structure of Escapades. (A) (A') Haploid cells expressing GFP-Esc1p from a galactose-inducible promoter (ATY3258) were induced for 5 hrs (left) or overnight (right) with 2% galactose. Escapades are seen as "fins" (F), "rings" (R) or "patches" (P). Phase images are in blue. Induction with 10–100-fold lower concentrations of galactose reduced the number of cells which were fluorescent but did not affect the appearance of their escapades. Note that fewer fins are seen upon overnight induction. The scale bar in this and all figures designates 1 micron. (B) Strain ATY2957 expressing both untagged Esc1p from a galactose-inducible promoter and a GFP-tagged ER marker (a truncated form of HMG-CoA reductase 1-GFP [59]), after overnight induction. Two cells are illustrated – one toward the upper right and one in the lower middle portion of the field. Note the ring-like escapades (e) in both cells. Fin-like escapades are seen after shorter periods of induction and no such structures are seen in the absence of galactose. The peripheral ER is indicated by the arrow. N: The nucleoplasmic volume. (C) Cells which express mRFP-tagged Htb2p and Nup49p-GFP as well as galactose-inducible untagged Esc1p (ATY3156) were induced overnight. Note the presence of the Nup49p-GFP signal (arrow) outside the margin of the red chromatin mass. By contrast, controls in glucose medium show a conventional circumferential distribution of GFP signal (not shown). (D) (D') GFP-Esc1p-expressing cells (ATY1483) were induced overnight, fixed and processed for transmission EM. Note the constant width of the double membranes that extend from the surface of the nucleus, and the presence of nuclear pores in these extensions (arrows). (E) Time-lapse sequence of a GFP-Esc1 expressing strain (ATY2102) after overnight induction. Note the progressive conversion of the fin to a ring-like escapade. Such conversions are seen only infrequently. N: The spherical portion of the nucleus. (F) (F') Htb2p-mRFP-expressing cells induced for 5 hr to express GFP-Esc1p (ATY3281). The square in the upper field is enlarged and illustrated without the green signal below to clarify the distribution of Htb2p-mRFP. Note the absence of tagged chromatin from the escapades.