tokens: Genetic analysis places CWH43 upstream of the BCK2 branch of the PKC1 signalling pathway , since cwh43 mutations were synthetic lethal with pkc1 deletion , whereas the cwh43 defects could be rescued by overexpression of BCK2 and not by high - copy - number expression of genes encoding downstream proteins of the PKC1 pathway However , unlike BCK2 , whose disruption in a cln3 mutant resulted in growth arrest in G ( 1 ) , no growth defect was observed in a double cwh43 cln3 mutants .