34 



routinely transferred every two days at a plating density of 



4 2 



1 x 10 cells/cm by trypsinization as described above. 



Mouse lymphocytic lukemia cells, EL4, were obtained 

 from the Salk Institute for Biological Studies, La Jolla, 

 CA. EL4 cells were grown as suspension cultures in RPMI 

 1640 with 10% FCS, penicillin and striptomycin . They were 

 transferred every three days at a final density of 1 x 10 

 cells/ml . 



Rat fibroblast cells, A-9, and an a-amanitin resistant 

 mutant of the A-9 line, LAN-2, were obtained from Dr. J. 

 Eisenstadt, Institute of Human Genetics, Yale University, 

 School of Midicine, New Haven, CT. The LAN-2 amanitin 

 resistant line contained RNA polymerase II activity several 

 fold more resistant to inhibition by a-amanitin in vitro 

 compared to the analogous enzyme from the parent line A-9, 

 (R. Bryant, personal communication). Both lines were grown 

 in Eagles MEM with Earle's salts, 10% heat inactivated FCS, 



penicillin and streptomycin. Stocks of A-9 and LAN-2 were 



4 

 transferred every three days at a final density of 1 x 10 



2 

 cells/cm by trypsinization as previously described. 



Inhibition of Cell Growth 



Inhibition of cellular proliferation by amanitin- 



protein conjugates was measured by determining cell numbers 



with an electronic particle counter (Celloscope, Particle 



Data, Inc.). For inhibition by ADH-BSA conjugates, cells 



were grown in sterile glass scintillation vials. Prior to 



each experiment AV3 and M-7 CHO cells were harvested by 



