Figure 3

Male germ cell-specific polyadenylation sites are not used in somatic cells. ATCC 3T3 cells (mouse embryonic fibroblasts) were transfected with reporter plasmids containing the polyadenylation cassettes indicated on the left and two days later RNA was extracted from these cells, cDNA was made, and 3' RACE was performed as described in Methods and Materials. Shown are the results of the poly(A) site identification. The open arrow on the bottom indicates the reported site of polyadenylation on that polyadenylation cassette. The black arrows on top represent the sites of polyadenylation identified in transfected cells. The black bar at SV40-mutant shows a mutation in the poly(A) signal (AAUAAA to GAGAAA) of the SV40 polyadenylation cassette.