pCL1 is a positive control plasmid that encodes the fulllength, wild-type GAL4 protein. The GAL4 protein activates reporter genes under the control of a GAL4-responsive element （UASG）. Thus, pCL1 is used as a positive control for the transcription assay in GAL4-based MATCHMAKER Two-Hybrid Systems. This vector is a derivative of YCp50 referenced in Fields & Song, 1989. pCL1 has not been sequenced.