Guanidine - Hel Extrac - tion of Proteins Expressed in Escherichia coli Using Polycistronic

by Northern blot analysis . Figure I shows part of the sequencing gel from the differential display experiments using chemiluminescent detection. Generally, about 100-200 bands were seen from the whole gel for each primer set; this number is about the same as with radioisotope detection (data not shown) ; most of the bands showed identical intensity among the cells examined. The band indicated by the arrow (CI) shows much higher intensity in PC3-PF, PC3-MF and DUl45 cell lines compared to the low tumorigenic and metastatic LNCaP cell line. The differential expression of this cDNA among the four cell lines was further confirmed by Northern hybridization (Figure 2). The confirmation rate of the differentially expressed cDNAs by Northern blots using our method is similar to that of differential display using radioactive detection (data not shown) . In conclusion, the method described here is a sensitive, reliable and safe alternative to the radioisotopic differential display technique; it has all the advantages of a nonradioactive method without sacrificing the sensitivity of radioactive detection. This method could be applied to any experiment where differential display technology might apply, particularly for those who wish to use nonradioactive procedures.