Fig. 2.

Effects of tags on protein levels. A, Protein extracts from heterozygous flies with insertions in Fer1LCH, Fer2HCH and Trailer hitch probed with Fer1LCH, Fer2HCH and Trailer hitch antibodies respectively to show the abundance of the tagged proteins (closed arrows) compared with the untagged proteins (open arrows). For a perfectly spliced and stable protein, the two band intensities would be expected to be equal. For Fer1HCH and Fer2LCH, tagged protein levels were 72 and 73% of the untagged, whereas for Trailer Hitch it was 19%. For Fer1HCH and Trailer hitch more than one fly line was available containing variants of the tag inserted; the figures are averaged from these lines. All these genes are predicted to encode single transcripts and protein products. Antibodies for Fer1LCH and Fer2HCH cross react with other proteins and extracts from untagged flies are run in adjacent lanes for comparison. B, Protein extracts from flies containing traps in growl and Rtnl1 (arrows indicate multiple isoforms) probed with anti-GFP to compare tagged protein levels with GFP, StrepII-tagged Venus YFP (SV), or FLAG-StrepII-tagged Venus YFP proteins. C, Confocal images comparing StrepII-tagged-venus proteins with (right) or without (left) FLAG. The addition of the FLAG tag does not reduce tagged protein levels. For these comparisons, the trap construct is inserted into the same intron and thus in the same position within the protein. Scale bars = 20 μm.