Northern blot analysis of transfected COS-1 cells. COS-1 cells were transiently transfected with pTH3/WT (WT) or pTH3/S572P (S572P) plasmid. Equal amounts of total RNA isolated from the transfected COS-1 cells were loaded in each lane, as shown by ethidium bromide staining (lower panel). The PLG mRNA was hybridized with a ³²P-labeled full-length PLG cDNA probe (upper panel).