Relative CCS4, CCDA, and CCS1 mRNA abundance in ccs4 and ccs4 (CCS4)-complemented strains. RNA was isolated and analyzed by real time PCR. Strains are wild-type CC124 (WT), ccs4-F2D8 arg7-8 (#1), ccs4-F2D8 arg7-8 strain transformed by cosmid pCB412 (#2), ccs4-F2D8 mutant (#3), ccs4-F2D8 arg7-8 strain cotransformed by pCB412 and pSK-CCS4 BamHI (#4), or cotransformed by pCB412 and pSK-CCS4 SacII (#5). Relative transcript levels (RTLs) represent the mean levels of three independent experiments, each analyzed in technical triplicates. RTL values are relative to the CBLP levels and were calculated as described in materials and methods. The abundance of UBQ2 is shown as a control.