Fig. 4.
Expression ofDrosophilaand human CTP synthase proteins. Expression of mCherry-tagged Drosophila CTPsyn (A) as well as human CTPS1 (B) and CTPS2 (C) in clone 8 cells shows cytoophidium formation. (D) Quantitative comparison of the filament length of Drosophila and human cytoophidia shows that CTPS1 filaments are shorter (~50%) than CTPsyn and CTPS2 filaments. The error bar show mean±s.e.m. At least 75 transgenic cells were counted in each case. Expression of Venus-tagged human CTP synthase (CTPS1, E) in clone 8 cells results in formation of filamentous cytoophidia while the A20R mutant protein (CTPS1A20R, F) forms cytoplasmic foci similar to the corresponding Drosophila protein. The amino acid sequence (1–20) of CTPS1 and the mutant construct is shown at the top of the panels with the mutated amino acid in red. DNA is shown in blue while the Venus-tagged proteins are in green. Scale bar=5 µm. (G) Western blot using extracts from cells co-expressing Venus- and mCherry-tagged CTPsyn proteins. The primary antibody used to stain the blot is shown on the right side of the panel.