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Figure
4. Analysis of Particle Movement
(A-G)
Wild-type yeast strain (K699) expressing both the ASH1 reporter
and the GFP-MS2 protein were observed with epifluorescence and bright
field microscopy. A cell with minimal nuclear signal was chosen so as
not to obscure the particle. Movement of the particle was recorded with
a video camera linked to a VCR. Images are presented at indicated intervals.
(A-F) Movement of the particle from the mother (nucleated) to the bud
(not nucleated). The mRNA particle was analyzed over a period of 4 min,
during which it moved a net linear distance of 4.4 µm in a time
of 128 sec, over a total pathlength of 23 µm.
A,
46s; B, 58s; C, 67s; D, 71s; E, 172s; and F, 211s. (G) A schematic diagram
recapitulates the particle movement over its total path (43 µm
per 240 sec). During the period of observation the 30 sec intervals
are represented beginning with the coolest colors (purple) and proceeding
to the hottest colors (red). The times representing A-F are indicated
as white dots on the travel line. The particle spends 180 out of 240
sec in the bud and about 60 sec localized at or near the bud tip. (H)
Strain K5209 containing a deletion of she1 analyzed by the same
approach showed significantly less net displacement and stayed within
the mother cell, never localizing to the bud tip. Bar, 2 µm.
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