Microinjection of cloned SV40 DNA fragments in the study of cell proliferation

DNA recombinant technology and the manual microinjection technique were used to study the base sequences in the SV40 early gene coding for cell DNA replication and nucleolar activation. Sequences critical for rRNA gene activation are located between nucleotides 3826 to 3506 (0.39-0.33 m.u.). Base sequences from nucleotide 4350 to 4190 (0.49-0.46 m.u.) are required for cellular DNA replication. Major T antigen determinant is coded by a sequence extending from nucleotide 4190 to 3880 (0.46-0.42 m.u.). Considering that an increase in cell size is regularly accompanied by an increase in the cellular amount of rRNA, nucleolar genes should be a target for growth-in-size signals. Therefore, the SV40 early gene presents a domain responsible for cell growth in size, and another separate but proximate region coding for cellular DNA replication.